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Home , Ballistics, Cartridge (firearms), Choke (firearms), External ballistics, Internal ballistics, Muzzle energy

7 and

Rachel Bolton-King1* and Johan Schulze2* 1Department of Forensic and Crime Science, Staffordshire University, Stoke-on-Trent, Staffordshire, UK; 2Veterinary Forensic and Wildlife Services, Germany and Norway

7.1 Crime Scene Evidence: Firearms and Ballistics by Rachel Bolton-King 82 7.1.1 Introduction 82 7.1.2 Firearms 82 7.1.2.1 Types of 83 7.1.2.2 Modern firing mechanisms 84 7.1.3 85 7.1.3.1 Composition 85 7.1.3.2 Live cartridges 86 7.1.3.3 Fired cases and 86 7.1.4 87 7.1.4.1 87 7.1.4.2 87 7.1.4.3 88 7.1.4.4 88 7.1.4.5 Production of residue (GSR) 89 7.1.5 Intermediate ballistics 89 7.1.5.1 Propellant and gaseous products 89 7.1.5.2 Projectile 90 7.1.5.3 Muzzle attachments 90 7.1.6 91 7.1.6.1 Muzzle and kinetic 91 7.1.6.2 92 7.1.6.3 Range 94 7.1.6.4 Accuracy and precision 94 7.1.7 95 7.1.7 Retrieval of fired ammunition components 95 7.1.8.1 Cartridges and fired cartridge cases 95

*Corresponding authors: [email protected]; [email protected]

© CAB International 2016. Practical Veterinary Forensics (ed. D. Bailey) 81 82 R. Bolton-King and J. Schulze

7.1.8.2 Fired projectiles and 96 7.1.8.3 Gunshot residue (GSR) 96 7.1.9 Conclusion 97 7.2 Wound Ballistics by Johan Schulze 99 7.2.1 Introduction 99 7.2.2 Basics of wound ballistics 99 7.2.3 Some specifics of wound ballistics 102 7.2.3.1 Deformation/fragmentation 102 7.2.3.2 Entrance and exit wound 102 7.2.3.3 Shotgun 104 7.2.3.4 Airgun 105 7.2.4 Essential steps of investigating a animal 106 7.2.4.1 Before necropsy 106 7.2.4.2 The practical approach 107 7.2.4.3 Recovery of 112 7.2.5 Conclusion 113

7.1 Crime Scene Evidence: Firearms ­ammunition and ballistics. The focus will and Ballistics be on the common types of firearm and asso- ciated ammunition that are utilized by ­civilians, which would ultimately be en- Rachel Bolton-King countered in the majority of cases where veterinarians are involved in forensic investi- gations. For more in-depth reading into this 7.1.1 Introduction field, recommended reading includes Farrar and Leeming (1983), Carlucci and Jacobson Crime scenes involving shooting-related in- (2008), Heard (2008), Haag and Haag (2011), cidents can contain a raft of forensic evi- Warlow (2011). dence that may be of benefit to the forensic veterinarian and criminal investigating team. The nature of the firearm (Section 7.1.2) and the ammunition (Section 7.1.3) utilized 7.1.2 Firearms in the shooting have a critical role to play in the resulting injury and trauma exhibited The legal definition of a firearm differs slightly in the body. from the dictionary definition. A firearm is The term ballistics is defined as the defined by The Firearms (Amendment) Act study of the of projectiles. Ballis- 1988 (UK Parliament, 1988) as ‘a lethal bar- tics is divided into three main categories: relled weapon of any description from which internal (Section 7.1.4), external (Section 7.1.6) any shot, or other can be dis- and terminal (Section 7.1.7); however, there charged’; whereas the Oxford English Dic- is also a fourth category known as inter- tionary (Oxford University Press, 2014) sim- mediate ballistics (Section 7.1.5). Terminal ply identifies a firearm as different types of ballistics (Section 7.1.7) covers both inani- , i.e. ‘a , or other portable gun’, mate objects and living organisms; however, thus ‘gun’ is defined as ‘a weapon incorpor- the study of projectiles through living organ- ating a metal tube from which bullets, shells, isms is classified as a sub-category of terminal or other are propelled by ballistics referred to as wound ballistics (see , typically making a characteristic loud, Section 7.2). sharp noise’. The mechanism of firing the The field of firearms and ballistics is projectile (Section 7.1.2.2) is unspecified; ­extensive. This chapter, therefore, aims to however, the legal definition implies that provide an introductory explanation of the weapon must be capable of killing a the scientific theory underpinning firearms, living target. The dictionary states that an Firearms and Ballistics 83

explosive force is required; however, the force may not have to be explosive in order to be lethal. The legislation around firearm ownership, transportation and use will vary Muzzle extensively depending on the region in which the crime occurred. Barrel

7.1.2.1 Types of firearm Tr igger The term is commonly used to de- scribe any firearm that is capable of being Frame fired from one hand (AFTE Training and Standardization Committee, 2007). This term includes two types of firearm: (or revolving pistol) and pistol, although the sub- (SMG) may also be con- Fig. 7.1.1. Annotated image of a Sig Sauer P226 sidered in this category. Within the UK, air semi-automatic pistol field stripped into its key are currently the most common component parts listed from top of the image; slide firearms utilized in gun crime as these are (containing the ejection port), barrel (with integral typically legal and unlicensed, but this is chamber), guide , frame and magazine closely followed by (Berman, (housed inside the grip of the frame). 2012; Smith et al., 2012) due to their small size, making them easy to conceal from and typically utilizes cartridges measured other civilians and law enforcement. Air in rather than calibre. Gauge equates weapons are typically used for recreational to the number of with the diameter use, such as target shooting, whereas hand- of the barrel bore, that collectively weigh are typically utilized for self-defence. 1 lb. The calibre is either the internal diam- The main difference between a pistol eter of the mouth of the cartridge case or the and a revolver is that a revolver has a maximum diameter of the projectile (units containing multiple chambers, each capable may be metric or imperial). For example, a of housing a single ammunition cartridge, 12-gauge shotgun has a barrel diameter of and the chamber is therefore separated from 0.729 in. and 12 lead balls of 0.729 in. weigh the barrel. A pistol has a single chamber that 1 lb. are usually single- or double- houses only one ammunition cartridge and barrelled with the latter having either a this is integrated into the barrel. A sub- side-by-side or up-and-over barrel align- machine gun is a shorter-barrelled, light- ment. Shotgun barrels also may contain a weight machine gun, designed to fire pistol-­ at the muzzle end, which can be inte- sized cartridges in short or long bursts of gral to the barrel or be removable. The choke fire. Modern handgun barrels are typically aims to force the multiple shot together rifled with a spiral internal surface profile prior to exiting the barrel and there are vary- consisting of alternating spiral lands and ing degrees of choke available. To be made grooves to enhance the ballistic properties of more concealable, criminals are known to the projectile upon muzzle exit. Figure 7.1.1 cut down and shorten the barrel length, indicates the key components common to a which will ultimately reduce the velocity, wide range of firearms. energy and range of the projectile(s) and in- also have a single chamber to crease the spread of lead shot fired from the house one cartridge, but are identified by ammunition due to excessively high their longer-rifled barrel and are larger (Haag and Haag, 2011) and choke removal. in overall size than handguns. Rifles are Tasers and stun guns may also be con- designed to be fired by one individual, but sidered as a firearm in some countries, in- using two hands. cluding Great Britain. Tasers are designed to A shotgun is differentiated from hand- fire two barbs from a cartridge, which are guns and rifles due to the smooth-bore barrel connected to the weapon by wire reaching 84 R. Bolton-King and J. Schulze

up to 10.6 m. When the wired barbs make the legal limits for an air weapon to be classi- contact with or penetrate the upper layer of fied as a firearm are higher than 1 ft lb (Home the skin (epidermis) the electrical circuit is Office, 2014). Criminal use of air weapons complete and current is passed through the was on the rise until 2003/2004 (Berman, target’s tissue to incapacitate. Tasers can be 2012), when legislation aimed to reduce this used in stun drive mode to cause pain, (Squires, 2014). However, injuries to animals whereby the cartridge is not used and con- caused by air weapons are still more com- tact is made directly between the skin and monly observed by veterinarians. To be legal the electrical device. and unlicensed, air must generate pro- Other weapons that could be considered jectile less than 6 ft lbs (8.1 J) relevant within the context of veterinary fo- and less than 12 ft lbs (16.3 J) for air rifles rensics are bows and crossbows, humane (Home Office, 2014). However, in Northern killers such as captive- guns (Warlow, Ireland, air weapons firing projectiles with 2011), weapons and paintball guns. muzzle energy greater than 1 J must be held However, by the UK legal definition these on a firearms certificate (Northern Ireland are not firearms and therefore not considered Office, 2005). within the scope of this chapter. The ammunition is loaded into the weapon either manually, or automatically from a magazine or of ammunition. Auto- 7.1.2.2 Modern firing mechanisms matic loading (self-loading) uses the energy created from discharging a previous cart- Firing mechanisms involve the loading of ridge to reload the next live cartridge of am- the projectile/ammunition into the weapon munition into the chamber ready to be fired and the functioning of all the firearm’s in- again. Heard (2008) and Warlow (2011) ternal components required to propel the discuss the range of firing mechanisms that projectile out of the barrel. Design and func- enable self-loading of ammunition and tionality of specific firearms is an extensive ­examples include recoil, and bolt-­ topic, ultimately determined by the firearm . Principally, there are two overarching manufacturer. Forensic veterinarians do not automatic firing mechanisms: semi-automatic need to know the in-depth details of all fir- and fully automatic. Semi-automatic means ing mechanisms, but need to appreciate that with one pull of the , one cart- the differences in the key firing mechanisms ridge is fired. With fully automatic, one and how these influence the ammunition pull of the trigger causes continual firing selected, the properties of the projectiles and reloading of ammunition until either the fired and the potential differences that trigger is released, or there is no ammunition could be expected for wound examination left to fire from the magazine or belt. There and interpretation. are some firearms designed to fire short Air weapons are relatively low-powered bursts of ammunition, whereby continual weapons, which use a high-pressure volume hold of the trigger will fire a small number of gas, typically atmospheric air or of cartridges (usually three to five); to fire dioxide, to transfer energy to the projectile further cartridges the trigger will need to () and propel it out of the barrel; these be released and pulled again. Modern weapons therefore do not require ignition of ­pistols such as Browning Hi-Power and Ber- chemical compounds to generate kinetic etta 92FS are commonly semi-automatic, energy. Air weapons using atmospheric air whereas SMGs such as MAC-10 and typically operate by manually compressing SMG may also have the capability of fully a spring; pulling the trigger releases the automatic fire and the AK47 assault rifle spring compressing the air and pushing it may have the additional option of short- behind the pellet. Alternatively, the pellet is burst fire. fired utilizing a small jet of compressed gas, For handguns, there are two ways to set such as carbon dioxide, released from a the trigger and fire the weapon: single-action small gas canister attached to the weapon and double-action. Single-action requires a when the trigger is pulled. In most of the UK, manual cocking of the and then a Firearms and Ballistics 85

subsequent pull of the trigger to fire. With ­designed first for a specific purpose; the weapon double-action, a longer and heavier pull of is developed later to fire that ammunition. For the trigger will first cock the hammer and example, Georg Luger developed the 9 × 19 then release the /striker on to the mm cartridge in 1902 which was later designed cartridge causing it to discharge. to be fired in the 1908 Luger P08 semi-automatic For rifles and shotgun, the firing mech- pistol (Jones and Ness, 2009; Bolton-King, anisms include single-shot, bolt-action (bolt 2012). Thus, a wide range of ammunition with a is turned to the cartridge into the breech variety of specifications has been developed end of the barrel before firing), self-loading for specific purposes (Table 7.1.1); choosing the (similar to self-loading pistols) and pump-­ correct ammunition for a specific weapon can action (breech is linked to the fore-end, which be critical to achieve the intended outcome. To when pulled back, unlocks the breech and ensure the weapon fires safely and correctly, ejects the cartridge case; pushing the fore-end the dimension(s) of the ammunition (calibre or forward loads in a live cartridge from the gauge) must be accurately selected for the fire- magazine and cocks the weapon). arm in which it is discharged. Other terms used to describe firearms and their firing mechanisms include converted 7.1.3.1 Composition (for example, a firing weapon converted to fire ammunition such as Olympic 38 or Modern ammunition has developed from Baikal), home-made, concealed (firearms made loading individual components (primer, propel- to look like other objects such as pen gun), de- lant and projectile) into a self-enclosed cart- activated (firearms made unable to fire -am ridge system to create a closed environment munition by machining/removing key compo- for a large amount of gas to be produced and nents), reactivated (deactivated weapons made allow the gas pressure to rise ­exponentially. to fire again) and imitation (firearms that look The core components of a cartridge are the real, but do not fire live ammunition). cartridge case and the projectile. The projectile is positioned at the mouth of the cartridge case and they are crimped together to form the cartridge. 7.1.3 Ammunition The base of the cartridge case houses the primer unit that contains the primer compound. Inside Like firearms, ammunition has developed the cartridge case, the propellant is confined over the centuries. However, ammunition is between the primer unit and the projectile.

Table 7.1.1. Common examples of modern ammunition calibres and their intended purpose.

Calibre (in.) Weapon Type (Centre-Fire) Purpose

0.22 Hornet Rifle Small varmint (<200 m) 0.223 Remington Rifle Military standard (long range) 0.303 British Rifle Military standard (long range) 0.357 Magnum Revolver Law enforcement (short range) 0.410 Shotgun Small varmint/game hunting 0.45 (ACP) Pistol Close combat, self-defence 0.458 Winchester Magnum Rifle Hunting dangerous game

Calibre (mm)

7.62 NATO Rifle Military standard (long range) 9 × 19 Pistol or sub-machine gun Military standard (short range)

Gauge

20 Shotgun Recommended for hunting novices 12 Shotgun Short range bird hunting 86 R. Bolton-King and J. Schulze

The primer (Section 7.1.4.1) and propel- fired from pistols, , rifles and ma- lant (Section 7.1.4.2) are both mixtures of chine guns are typically referred to as bullets. chemical compounds designed to ignite, burn Shotgun ammunition, however, commonly and provide oxygen to the combustion pro- contain multiple spherical lead pellets known cess. Priming compounds are typically inor- as shot. However, some shotgun cartridges are ganic compounds that are explosive and designed to fire a single projectile () from more exothermic, whereas propellant flakes a rifled-barrel shotgun, commonly used for are organic in nature, burning slower and beast destruction. slightly cooler. There are two main classifications of 7.1.3.2 Live cartridges modern cartridge: centre-fire and -fire. The difference is due to the location of the Although fired cartridge cases and fired pro- explosive primer that ignites the cartridge. jectiles (Section 7.1.3.3) are the primary As the name implies, the centre-fire cartridge types of forensic firearms evidence recovered has the primer located in the centre of the from crime scenes, the presence of unfired base, whereas the primer within the rim- (live) cartridges is important to forensic fire- fire cartridge has it located around the rim. arms examiners. Live cartridges allow an Projectiles are identified for ammunition examiner to determine exactly the type of based on the intended functional purpose of ammunition that was used by the firer and the cartridge and the weapon type the cart- can be used for corroborative intelligence ridge is designed for. Projectile shape, dimen- and for test firing to assist in the identifica- sions and material properties affect the tion of a specific weapon. external (Section 7.1.6) and terminal ballis- tics (Section 7.1.7) following projectile exit 7.1.3.3 Fired cartridge cases from the barrel. Typically the softer the ma- and projectiles terial property of the projectile, the more easily the projectile will deform on impact Brief examination of fired cartridge cases with a target, increasing surface area and can provide valuable intelligence to the increasing the amount of energy that can be forensic practitioners investigating the inci- transferred into the target material. For ex- dent. Information can include the manufac- ample, a full metal jacketed (FMJ) projectile turer and calibre of the likely ammunition is harder than a metal jacketed hollow-point used, and probable identification of the type (HP) that has an exposed lead cavity at the of weapon, its manufacturer and model, using projectile nose. The HP will deform and mush- class characteristics transferred during the room on impact with a target, significantly firing process (for example, the shape and reducing penetration depth and increasing dimensions of the firing pin impression). wounding in comparison to an FMJ. This Knowledge of such initial intelligence can makes the FMJ more suitable for military aid the forensic veterinarian in their exam- use and the HP more suitable to law enforce- ination of wounds (Section 7.2). ment and hunting, where only one target The fired ammunition component that needs to be hit. is more commonly encountered by a forensic Air weapons do not utilize a cartridge veterinarian is the fired projectile, which system, as the compressed air supplies the may or may not be located inside the ­injured force to propel a single lead pellet using com- species. Ideally, the presence of a forensic parably low gas pressure. More lethal firearms firearms examiner or ballistics expert would utilizing cartridge-based ammunition create be very beneficial as they can assist with much higher gas during ignition, wound examination and interpretation and therefore have greater , and recover any firearms-related evidence; muzzle energy, range and penetration depth. however, the overriding purpose of the veter- However, research has shown that even blank inarian is to preserve life. As a minimum, an firing weapons can be fatal, due to the gas pres- X-ray of the wound should be undertaken, sures released (Demirci et al., 2011). Projectiles as some initial visual analysis of the X-ray Firearms and Ballistics 87

images can provide intelligence to the prac- will not explain these concepts in depth, titioner during their examination. The approxi- but will introduce the various stages that mate dimension of the base of the projectile comprise the ignition of typical modern can indicate the calibre of the weapon, and cartridge-based ammunition. the shape of projectile found may lead to the type of weapon that discharged it. Also, it is 7.1.4.1 Primer possible that the projectile may have frag- mented inside the body; this could be due When the base of the cartridge is struck by to the design of the ammunition component the firing pin, this creates an impression in or because the projectile has struck dense the metal base known as the firing pin im- material within the body; for example, bone. pression. The distortion to the base causes Retrieval of fired projectiles will be covered the case to strike a metal anvil positioned in Section 7.1.8. directly beneath, within the primer unit, thus Although beyond the scope of this chap- creating a . The spark detonates the un- ter, submission of fired cartridge cases and stable, explosive inorganic primer producing projectiles to the laboratory for examination a flame jet of approximately 2000°C (Heard, by a firearms examiner can further identify 2008). the specific weapon that was involved using The primer mixture comprises an microscopic examination of the individual ­igniter, an oxidizer and a . The igniter is characteristics engraved and impressed into an explosive chemical compound such as the fired ammunition component. Individual lead styphenate or tetrazine (in lead-free am- characteristics are created by unique tool- munition). Barium nitrate is an oxidizer that marks generated on the surface of the weapon aids flame production by providing oxygen components during the component manufac- during the , and sulphide turing process. The toolmarks are randomly is an example of the fuel needed to increase created due to wear of the tool surface used the and length of the flame. to manufacture the component and these The flame is forced through one (boxer toolmarks are transferred to the component primer type) or two (berdan primer type) during the firing process. As they are random flash holes in the top of the primer unit, and unique, the individual characteristics can which provides sufficient thermal energy to be used to identify a specific weapon compo- ignite the propellant flakes housed in the nent. Even if a firearm is not recovered, exam- main body of the cartridge case. ination of multiple fired cases or projectiles can be used to link shooting incidents to- 7.1.4.2 Propellant gether and identify a single weapon used in one or more incidents, known as an inferred Propellant is compressed grains of organic weapon. materials designed to burn at a controlled rate. In modern smokeless propellant (as op- posed to black powder), and/ 7.1.4 Internal ballistics or nitroglycerine is the main component. The shape and dimensions of the grains Internal ballistics covers all aspects involv- (ballistic size) and presence/absence of mod- ing the ammunition and firearm from the erators, stabilizers and/or retardant chemicals moment the firing pin strikes the cartridge within or coated on the grain surface(s) can to the point at which the projectile exits the control the burning rate of the propellant. muzzle of the firearm. A range of scientific As the grains combust, they produce a large concepts underpin internal ballistics, which volume of gas (primarily carbon dioxide include combustion theory, Piobert’s law of and water vapour), which is sealed inside burning, the ideal gas law, laws of thermo- the cartridge case and chamber of the firearm. dynamics, conservation of energy and linear The temperature and pressure builds inside , and ’s laws of physics the cartridge, thereby increasing the burn- (Carlucci and Jacobson, 2008). This section ing rate of the propellant and resulting in an 88 R. Bolton-King and J. Schulze

exponential rate of combustion. The initial The precise velocity of the projectile prior rate of combustion is also determined by the to exit will vary to some extent from the am- ratio between propellant volume and case munition manufacturer’s specifications, de- volume; a greater volume of unfilled pending on the specifications of the model in the cartridge case will result in a slower of firearm the ammunition is fired from. For combustion rate, as the gas has more space example, for a given cartridge, the tighter the to fill before the pressure can start to rise. fit of the projectile within the barrel bore, the When the pressure is high enough in the cart- greater the level of initially acting ridge it the projectile(s) free from the against the forward motion of the projectile, cartridge case; this is known as shot start and therefore the lower the muzzle velocity. (Farrar and Leeming, 1983). If the barrel is longer, then frictional force may act for longer. There will also be some vari- 7.1.4.3 Projectile ability from cartridge to cartridge due to the tolerances during ammunition production and At shot start, the projectile(s) starts to travel how the cartridge seats in the breech of the down the barrel of the weapon and accelerates weapon. due to the work done by the high-pressure gas on the entire surface of the projectile 7.1.4.4 Weapon base, which increases energy transferred to the projectile. Due to the increase in space The of the primer, combustion of behind the projectile, the pressure is still the propellant and friction generated (typic- rising, but the propellant starts to burn at ally for rifled barrels) between the barrel and an increasingly slower rate. Peak pressure the projectile will transfer thermal energy occurs approximately 0.5 ms after cartridge to the metallic firearm components, primarily ignition and can be in excess of 300 MPa the chamber and barrel. Lawton (2001) indi- (Warlow, 2011). cates barrel bore in the region If the barrel is rifled (see Section 7.1.5.2) of 1100°C, whereas Warlow (2011) suggests then there will be some friction when the over 2200°C. Contact between firearm com- projectile engages with the slightly smaller ponents and ammunition, together with dimension of the barrel bore created by these extreme temperatures, even over such lands of the barrel . Some gas will es- a short period of time, will cause surface cape in front of the projectile through the melting and enhanced wear of the weapon grooves of the rifling as these may be deeper components. than the maximum diameter of the project- When the propellant combusts, the pres- ile. If the barrel is smooth bore and multiple sure of the gases does not only act in the projectiles are fired from the cartridge, as direction of the projectile base, but in all with a shotgun, some gas may escape by directions around the breech of the weapon. passing between and around the shot inside As a result, while the projectile remains inside the barrel. the barrel, the pressure exerted forwards At the time of peak pressure, the pro- on the projectile is experienced backwards jectile may have only moved 2 cm. As the on the weapon, known as recoil. Typically, the projectile accelerates and level of kinetic greater the recoil velocity, the more uncom- energy overcomes the initial frictional force, fortable the weapon is to fire. The production an increasing volume will be left behind the of high-pressure gas or recoil energy gener- projectile and the rate of burning continues ated can be exploited in the weapon design to reduce as the propellant flakes reduce and be utilized by the firing mechanism to in size and produce less gaseous products. eject fired cartridge cases after discharge and Providing sufficient force is maintained as load new cartridges (auto-loading). the propellant burns, the projectile(s) will pass As the pressure acts in all directions, the down the barrel to the muzzle exit within muzzle of the weapon will also lift slightly 2 ms from the strike of the firing pin (War- above its point of aim, especially if the low, 2011). muzzle end of the weapon is unsupported. Firearms and Ballistics 89

Barrel lift will vary depending on the am- 2008) classifies intermediate ballistics as an munition utilized and will ultimately affect area in its own right. The time and distance shooting accuracy. This needs to be con- that intermediate ballistics covers will vary, sidered when sighting the weapon and fir- depending on the type of ammunition used ing in automatic modes. and the ballistic properties of the projectile. This section will briefly discuss how the flow 7.1.4.5 Production of gunshot of gaseous combustion products and presence residue (GSR) of muzzle attachments influence propellant particles and the motion of the projectile The inorganic primer and organic propellant upon muzzle exit. will not completely burn during ignition of the cartridge. This generates a mixture of 7.1.5.1 Propellant particles and unburnt, partially burnt and still burning gaseous combustion products particles, referred to as gunshot residue (GSR) or firearms discharge residue. GSR will also As previously discussed, high-pressure com- contain some of the metallic particles pro- bustion products escape the muzzle in front duced from the wear of the firearm compo- of the projectile due to the high pressure re- nent surfaces, together with the ammunition lease of gas after shot start, together with a materials removed by striated contact with column of air that is pushed forwards by the the weapon components, such as the barrel. moving projectile. When these high-pressure GSR particles predominantly exit the weapon gases exit the muzzle, a shock wave (precur- once the projectile has left the muzzle, but sor blast shock) is created just in front of the some will escape before the projectile(s) exits muzzle, travelling slightly above 340 m/s and GSR will be carried by the escaping gas- ( of sound) and meets with the ‘normal’ eous combustion products in gaps between atmosphere. This shock wave generates a the projectile(s) and bore surface. GSR will sonic bang and radiates out in a spherical also exit from any opening within the fire- direction away from the muzzle. arm, such as the ejection port (semi-automatic Precursor bottle shock and the Mach weapon) or cylinder (revolver). disk also occurs around the muzzle as the Partially burnt and still burning particles precursor blast shock is trying to travel are important with respect to intermediate back inside the barrel, against the flow of gas ballistics (Section 7.1.5), as well as being (Carlucci­ and Jacobson, 2008). The bottle significant to forensic investigation. In the shock increases as the gas velocity increases; context of veterinary forensics, presence or as gas velocity reduces the bottle shock will absence of GSR can assist with determining eventually shrink back inside the barrel. firing distance between muzzle and the tar- When the projectile exits the muzzle, get, differentiating between initial entry and the gas seal is broken and a further release of exit wounds and identification of the type highly pressurized gas is released into the of ammunition used (Heard, 2008; Broz˙ek-­ atmosphere. A second high-pressure blast wave Mucha, 2009; Dalby et al., 2010; Haag and is formed, together with further bottle shock Haag, 2011; Warlow, 2011). and Mach disk. This second blast wave is higher in pressure than the precursor blast wave and is initially non-spherical due to 7.1.5 Intermediate ballistics the projectile and flow of combustion gases. This blast wave accelerates the combus- Intermediate ballistics is a transitional area tion products forwards, creating a turbulent covering the moment the projectile exits the column of gas. The column of gas initially barrel until the projectile is considered to overtakes the projectile, causing a shock wave be in free . Heard (2008) encompasses around the base of the projectile (stern shock), intermediate ballistics within the scope of which can accelerate the projectile and pro- wider external ballistics, whereas more spe- duce instability and yawing. The spherical cialized literature (Carlucci and Jacobson, blast shock is travelling faster and has more 90 R. Bolton-King and J. Schulze

energy than the precursor blast shock and the nose to rise or fall above or below the catches up with it; shock waves lose energy projectile’s line of flight base, which increases and velocity as they increase in size and the the surface area presented at the projectile gas molecules dissipate. nose. Such increase in surface area increases Within the gaseous combustion prod- the air resistance around the projectile, redu- ucts, still burning propellant particles are also cing projectile velocity and, without a rota- present. These particles exit from the barrel tional force about the centre of , this in front of the projectile, but are predomin- would cause the bullet to tumble. Tumbling antly built up behind the projectile. As these would ultimately reduce projectile velocity, particles pass through high-pressure shock energy, distance (range), accuracy, precision waves, their temperature and burning , but increase damage/wound poten- increases producing visible light (incan- tial due to an increased surface area upon descent radiation), known as . contact with the target. Preflash can occur before the projectile exits To counteract destabilization, the rifling the muzzle, but primary muzzle flash occurs inside the barrel consists of spiral lands and at the muzzle of the firearm after projectile grooves. The higher-profile lands on either exit. Intermediate muzzle flash can occur side of the grooves in the barrel bore are further from the muzzle. As the gases in the smaller in diameter compared to the max- bottle shock expand rapidly they cool down imum diameter of the projectile and therefore and a faint muzzle glow can be seen moving engrave into the surface of the projectile, away from the muzzle. gripping the projectile and bringing about Once all the combustion products have rotation as the projectile travels down the been released from the barrel, there is a void barrel. Upon muzzle exit, the projectile will in the barrel bore. As the blast shock radiates be rotating at a pre-defined rate. This rota- out in all directions, the blast wave can then tion helps to re-stabilize the projectile as recede down the empty barrel along with it travels through the turbulent gas due to some of the combustion products. If a target gyroscopic nutation and thus, the rate of is in close proximity to the muzzle upon dis- rifling twist down the barrel is important charge, it is this vacuum effect which sucks for optimum stabilization of the projectile. the target material back inside the barrel, Depending on the muzzle velocity of which can therefore be of forensic significance the projectile, the projectile will either not when interpreting the shooting incident. reach the blast wave (subsonic projectile), or overtake the blast shock (supersonic pro- jectile) and generate a shock wave and 7.1.5.2 Projectile audible sonic bang from the nose of the pro- Upon muzzle exit, the projectile is in a tur- jectile. With supersonic projectiles, a further bulent atmosphere and is therefore not fully shock wave and sonic bang will be created stabilized. This can have varying degrees of when the base of the projectile subsequently impact on the projectile, depending on its passes through the blast shock. shape. For example, cannonballs and shot are typically spherical and therefore turbulence 7.1.5.3 Muzzle attachments will affect the object similarly in all directions. Heard (2008) indicates there are six types With most other types of projectile, however, of muzzle attachment for pistols, revolvers, they are designed to be aerodynamic and rifles and shotguns: stable during free flight and may have charac- teristic features (such as fins) on the surface to 1. sound suppressors. ensure that the projectile arrives at the target 2. recoil reducers (compensators). nose first. 3. flash hiders. Turbulence created by the combustion 4. muzzle counter weights (to reduce muzzle products initially destabilizes these projectiles, lift). causing the projectile to yaw slightly (1.5° 5. grenade dischargers. for a 0.303-in. rifle bullet (Heard, 2008)), i.e. 6. recoil boosters. Firearms and Ballistics 91

Only the first three will be discussed here, 7.1.6.1 Muzzle velocity and as these have a direct influence on intermedi- ate ballistics. During internal ballistics, approximately Sound suppressors are predominantly 30% of the energy created is actually trans- designed to reduce noise generated from an ferred to the projectile(s) (Warlow, 2011), expanding gas pressure wave by 18–32 dB predominantly in the form of kinetic energy, (Heard, 2008). They also act to reduce flash resulting in of the projectile(s) and recoil to some extent. Such attachments to a known velocity. Following muzzle exit lower the energy of the gas by allowing the and a very short distance past the muzzle, gases to expand within a closed container, the projectile reaches a maximum velocity, by increasing the volume the gas flows into referred to as muzzle velocity. Muzzle vel- or by making the gas do mechanical work ocity is pre-determined by the ammunition (moving a rotor, for example), or by reducing manufacturer; however, as previously ex- the temperature through absorption. Those plained, fired projectiles may not reach the suppressors that are built into the barrel can technical specification of muzzle velocity also reduce the muzzle velocity of the pro- quoted by the ammunition manufacturer. jectile to less than the , Kinetic energy and muzzle velocity are thereby preventing the supersonic boom of two of three linked factors; the third compo- firing by bleeding off some gas near the muz- nent that affects muzzle velocity and the zle of the weapon. kinetic energy is the projectile mass. Kinetic Recoil reducers (or muzzle brakes) are energy is calculated by squaring the vel- designed to direct the muzzle gas sideways ocity and then multiplying this by half the rather than in a primary forwards motion. mass of the projectile. As the mass of the Gas deflection is obtained by placing one or projectile increases, a greater amount of more sets of symmetrical ports along the work, force and energy is required to move sides of the muzzle attachment for gases to the projectile the same amount. Therefore, escape. for two projectiles of different to Modern flash hiders are usually the sim- have the same muzzle velocity, more kinetic plest type of muzzle attachment. These energy (and therefore a higher gas pressure) devices are primarily designed to reduce is required to fire the heavier projectile. intermediate muzzle flash by dispersing the A projectile with higher mass will ultimately muzzle gas and breaking up the barrel shock enhance its ‘carrying power’ (Heard, 2008). and Mach disk. They are usually cone-shaped, When considering terminal ballistics a tube with odd-numbered slots, or a bar later on, the kinetic energy of the projectile style (Farrar and Leeming, 1983; Carlucci is of greater importance than the velocity of and Jacobson, 2008). the projectile, as kinetic energy takes into account both projectile mass and velocity. It is also the ability of the projectile design to transfer energy to the other object that im- 7.1.6 External ballistics pacts on the resulting damage to the object. As soon as the projectile exits the muz- External ballistics covers the period of zle, the energy and force acting on the pro- flight from the point at which the projectile jectile is in the forwards (horizontal) direc- is stable and behaving within ‘normal’ at- tion away from the muzzle, therefore the mospheric conditions until the moment it velocity vector has a positive value. Initially comes into contact with an object. Like this will be the dominant direction of force internal ballistics, this aspect is very com- acting on the projectile. However, unless plex and involves extensive mathematical the projectile is fired into a vacuum, there computation to determine a projectile’s flight will always be forces acting against the pro- path. This section considers basic concepts jectile in the opposite direction limiting the that critically underpin this area of applied ­forwards progression, reducing the kinetic physics. energy and therefore the velocity of the 92 R. Bolton-King and J. Schulze

projectile over time. These opposing forces a long, sharp and low-angled nose () to are from the interaction with molecules reduce the cross-sectional surface area ini- within the atmosphere; the phenomenon is tially presented to the air and may even have known as air resistance (). The forward a slightly angled base (boat-tail) to improve movement of the projectile compresses the the flow of air particles and reduce turbulence air molecules in front of it causing areas of from air molecules behind the projectile. higher pressure which act in all directions The term is used to cal- around the front of the projectile. Minimiz- culate the decline in projectile velocity due ing the cross-sectional area of the projectile to the air, and takes into account projectile and making the projectile less angular will mass and diameter (Carlucci and Jacobson, reduce air resistance. The air molecules then 2008). Typically, the higher the ballistic flow around the projectile, a small amount coefficient, the better a projectile retains its of surface (skin) friction is created between velocity over time. Using data provided by the air molecules and the sides of the pro- Forker (2010), Table 7.1.2 and Fig. 7.1.2 jectile, further reducing the kinetic energy illustrate how the projectile energy changes and velocity of the projectile. for some common cartridges. When the air molecules have passed over the sides of the projectile, they have to fill in the space left by the base of the project- 7.1.6.2 Trajectory ile. This again causes high-pressure regions at the back edges of the projectile and leaves Air resistance is not the only force acting on a turbulent wake of gas behind the project- the projectile. Acceleration due to gravita- ile. The shape of the nose and base of the tional pull from the Earth is constantly act- projectile are therefore critical to limiting ing downwards in the vertical direction on the effect of air resistance on the kinetic en- the unsupported object at 9.81 ms–2 (Haag ergy and velocity of the projectile. A more and Haag, 2011). As a result, the natural aerodynamically shaped projectile will flight path or trajectory will always ultim- exhibit a slower decline in velocity and ately curve downwards towards the ground kinetic energy due to air resistance. Aero- (bullet drop), unless the trajectory is prema- dynamically shaped projectiles will display turely interrupted by an object.

Table 7.1.2. Examples of various cartridges.

Bullet Muzzle Muzzle Firearm Projectile Weight G1 Ballistic Velocity Velocity Type Cartridge Manufacturer Type (g) Coefficient (fps) (m/s)

Revolver 0.357 Magnum Sellier and FMJ 158 0.154 1263 385 Bellot Pistol 0.45 ACP American Eagle FMJ 230 0.178 890 271 (Federal) 9×19 mm Sellier and FMJ 115 0.102 1280 390 Bellot Rifle 0.22 Hornet Sellier and FMJ 45 0.102 2346 715 Bellot 0.223 Remington American Eagle FMJ 55 0.270 3240 988 (Federal) Boat-tail 0.303 British Sellier and FMJ 180 0.564 2438 743 Bellot 0.458 Winchester DGX 500 0.295 2260 689 Magnum 7.62 mm NATO American Eagle FMJ 150 0.409 2820 860 (Federal) Boat-tail Firearms and Ballistics 93

(a) 8000

7000

6000

(J) 5000 gy

4000

3000 Pr ojectile ener 2000

1000

0 0 100 200 300 400 500 600 700 800 900 Distance from muzzle (m)

0.22 Hornet (FMJ) 0.458 Winchester Magnum (DGX) 0.223 Remington (FMJ Boat-tail) 0.303 British (FMJ) 7.62 mm NATO (FMJ boat-tail)

(b) 800

700

600 y (J)

500

400 Pr ojectile ene rg

300

200 02550751000 125150 175 Distance from muzzle (m)

0.357 Magnum (FMJ) 0.45 ACP (FMJ) 9×19 mm (FMJ)

Fig. 7.1.2. Projectile energy changes for some common cartridges. 94 R. Bolton-King and J. Schulze

The initial projectile trajectory will be projectiles are most influenced by wave affected by the muzzle firing (angle of drag, and therefore the nose of supersonic inclination). However, it is typical for the projectiles needs to be designed to minim- projectile not to exit the muzzle aligned ize drag. with the bore so it will experience vertical Angle of inclination has a significant role and lateral jump (Carlucci and Jacobson, in the maximum potential range of fire for a 2008) caused by air resistance. Considering projectile. For a specific projectile fired in a only the effect of vertical gravitation force vacuum on Earth, the time spent in free flight on a projectile fired in a vacuum at 45°, for for the same ammunition will be identical, but example, the trajectory would be a symmet- the maximum range will be obtained when rical parabolic curve about a peak height. there is as much forwards motion as vertical In atmospheric conditions, this para- motion. Maximum theoretical range will bolic curve is no longer symmetrical due to therefore occur at 45° inclination due to the the effect of air resistance (wave drag, base trajectory’s symmetrical shape; 30° and 60° drag and skin friction). The forces counter- firing will result in identical, but acting the forward motion of the projectile ­reduced, range of fire compared to 45°. will cause the projectile not to reach as high Considering the impact of firing angle vertical distance or as long horizontal dis- alone in atmospheric conditions, maximum tance (range). The velocity of the projectile range will typically be generated when fired will reduce over the time of flight at an ex- between 27° and 30° (Carlucci and Jacobson, ponential rate; therefore, the faster the muz- 2008), although Haag and Haag (2011) indi- zle velocity of the projectile, the greater the cates 30° to 35° for handgun cartridges. The velocity lost per unit of time. accent of the projectile to peak height will Many firearms are discharged at relatively be slightly lower and of less distance com- low-angle (flat) over relatively pared to in the vacuum, but the biggest effect short range; however, when the target is to range occurs during projectile descent to positioned at a significant range or the pro- ground. Pistol and revolver bullets, when jectile needs to travel over obstacles in the fired at their optimum departure angle can line of sight, higher angles of trajectory are reach a maximum range of 1000–2000 m, employed, exploiting the curved trajectory. whereas rifle bullets can reach between 3000 m and 4000 m (Haag and Haag, 2011). Shot need to be considered separately. 7.1.6.3 Range Shot are spherical, symmetrical and do not require stabilization by rotational force. Maximum effective range of real projectile Spheres are less aerodynamic, and these trajectories can be difficult to calculate. projectiles are not designed to be fired over Range is affected by the muzzle velocity, the long distances. Their maximum range in air mass, shape and cross-sectional area of the has been demonstrated to be 1–3% of the projectile. Other effects include altitude, range achieved if fired in a vacuum (Chugh, barometric pressure, crosswind, 1982) compared to approximately 20% for and temperature. However, to consider the bullets. As there are multiple projectiles, effects of all these variables is outside the shot spread out over range and can be used scope of this chapter. more effectively for distance determination As velocity is calculated by dividing (Çakir et al., 2003; Haag and Haag, 2011). distance by time, the greater the velocity of the projectile, the further the projectile will 7.1.6.4 Accuracy and precision travel in a set period of time. To maximize range, the aerodynamic shape and geometry The accuracy (closeness to the intended point of the projectile are critical depending on of impact) and precision (spread around the projectile muzzle velocity (subsonic or super- intended point of impact) of the projectile sonic). Subsonic projectiles are most influ- will be affected by the firer, weapon and at- enced by base drag, whereas supersonic mospheric conditions, including speed Firearms and Ballistics 95

and direction, the extent of which is outside bullets) are designed to mushroom at the nose the scope of this chapter; however, some to increase surface area and increase the examples are considered. transfer of energy from the projectile to the The weapon type is important to con- target. The consequence is a greater damage/ sider. Handguns are typically designed for wounding potential. FMJ projectiles, how- close combat and therefore less accurate and ever, are not designed to deform on impact precise over distance than rifles. Generally, and therefore do not transfer as much energy this is due to the shorter barrel and less aero- into the target, ultimately reducing the dam- dynamic projectiles. By design, shotguns fir- age/wound potential and increasing the depth ing a number of shot are primarily used for of penetration into the target. hunting and therefore accuracy and preci- The angle at which the projectile hits sion are less critical as there are multiple shot the target also affects whether the projectile that spread out as range of fire increases, and is more likely to penetrate into the target or therefore the shot are more likely to pene- ricochet, i.e. deflect off the target surface. trate and strike the animal. For every combination of specific projectile Firing a brand new weapon from a design and target surface, there will be a fixed firing position should provide excel- critical angle that determines whether the lent accuracy and precision. Over time, as projectile penetrates or has the potential to weapon components such as the barrel suf- ricochet. Generally, the critical angle will be fer from wear, the tolerance to generate a relatively low (oblique) and the projectile stable projectile during flight increases typically ricochets off at a comparably and this has a negative effect on accuracy lower angle (Haag and Haag, 2011). and precision. Incorrect support, hand- The effect of ricochet and tumbling will ling and aim of the weapon during firing affect the size and shape of penetrating (Goonetilleke et al., 2009) will reduce ac- wounds (Section 7.2). Tumbling or instabil- curacy and lower precision due to recoil ity in a projectile will cause it to yaw. If the forces, whereas reducing the trigger pull projectile hits an animal in a state of yaw force required to action the trigger mechan- rather than perpendicular and nose first, ism and discharge a round can increase the surface area where impact occurs is in- precision and accuracy. creased and therefore the size of the entry wound may be increased. Such impact angle can also transfer energy into the animal/target more effectively. However, 7.1.7 Terminal ballistics if the projectile is designed to transfer energy effectively (for example, a hollow-­ Energy and design of the projectile as well point or soft-point) then the energy trans- as the , material properties and sur- fer may be less effective as the nose will face roughness will affect what happens to not be able to perform as designed. the projectile when it hits a target surface. Target materials that are less dense and more malleable than the projectile mater- 7.1.8 Retrieval of fired ammunition ials are more likely to deform, be pene- components trated to some extent and absorb more en- ergy from the projectile, compared to those 7.1.8.1 Cartridges and fired that are denser and have greater hardness. cartridge cases Yielding surfaces that deform upon impact produce greater angles of projectile rico- If you are called to a crime scene of a sus- chet than unyielding surfaces (Haag and pected shooting, the forensic veterinarian Haag, 2011). should be aware of the potential for finding The design of the projectile will have live ammunition as well as fired cartridge an effect on the potential for ricochet. Some case evidence. Depending on the nature of projectiles (e.g. soft-point or hollow-point the scene and the location of the incident 96 R. Bolton-King and J. Schulze

geographically, there will be a variety of (Wightman et al., 2013) and the thickness policies governing who recovers this phys- and material properties of their skin will in- ical evidence. The purpose of this section is fluence the ability for the pellet to pene- to remind the practitioner that such evidence trate, together with the energy and shape of has forensic value in inferring the calibre the projectile. and type of firearm likely to have discharged As previously stated, any fired project- the cartridge, the number of weapons in- iles recovered should be handled with plas- volved, and has the potential to link crimes tic tweezers or forceps to prevent damage to utilizing discharge of the same weapon in the forensic characteristics. Upon recovery various cases; and microscopic examination of the projectile, this should be washed with of fired cartridge case evidence can uniquely sterile water to remove biological hazards identify the firearm that discharged it, if a (different protocols are required for project- weapon is ultimately recovered. ile retrieval from humans) and air-dried If unfired ammunition is discovered, before packaging, to prevent any the cartridges need to be recovered using of the projectile material surface. Packaging good practice to minimize contamination, for fired projectiles is ideally in polythene such as wearing gloves, and should be pack- and containers, i.e. not containing aged separately to any weapon recovered to cotton wool. minimize risk and prevent accidental firing. Wadding components within shotgun Cartridges should be packaged in paper bags, cartridges are ejected from the cartridge along cardboard boxes or plastic containers (Tilstone with the single slug or multiple shot. This et al., 2013) lined with non-abrasive­ material can travel over 30 m from the muzzle of the (not cotton wool) to prevent them rolling weapon (Bonfanti and De Kinder, 2013) and, around during transportation. therefore, finding wadding inside a wound If fired cartridge cases, shotgun wad- tract or permanent cavity can imply that ding (typically made of fibre or plastic) and/ the weapon has been discharged at close or projectiles are observed in the scene sur- range to the target. Recovery and packaging roundings they should be recovered using of shotgun wadding should be as described plastic forceps or tweezers, to prevent dam- above for fired projectiles. age to the evidence surface (Bruce-Chwatt, 2010). Handling items with metal tweezers 7.1.8.3 Gunshot residue (GSR) of a harder material than the evidence may cause permanent toolmarks on the evidence GSR can be sampled with commercially surface, that could damage or impede foren- available GSR collection kits by swabbing sic examination and interpretation subse- around the area of the wound entry. GSR quently undertaken by firearms examiners. may be differentiated from other metallic Fired cartridge cases, like the cartridges residues (Romolo and Margot, 2001; Dalby themselves, should be packaged as they are et al., 2010; Grima et al., 2012) and can recovered from the scene in paper bags, sometimes be uniquely identified to a type cardboard boxes or plastic containers lined of ammunition (Brozek-Mucha and Jankow- with polythene/non-abrasive material (not icz, 2001); for example, if the composition cotton wool), with the latter preferably used of the primer is very distinctive. GSR can be for fired projectiles and wadding. indicative of close range of fire (Ditrich, 2012), as can the presence of stippling, pow- 7.1.8.2 Fired projectiles and der tattooing on the skin and burning of hair shotgun wadding from burning propellant flakes and hot gases released from the muzzle of the firearm. Fired projectiles, such as bullets, pellets (air However, if an air weapon was utilized, such weapons), slugs or shot (shotgun) may be characteristics will not be present around present in the animal. Even legal unlicensed an entry wound, even at close proximity, as air weapons can penetrate animal skin, but there is no combustion of propellant used to research has shown that the type of animal propel the pellet out of the weapon. Firearms and Ballistics 97

7.1.9 Conclusion computer tomography (CT) and ultrasound, should be employed at the earliest oppor- This section aimed to introduce some of tunity. Use of such technologies facilitates the key scientific principles underpinning the formation of the forensic examination shooting incidents that may influence strategy by providing visualization of bullet-­ observed wounding in animals. Variations wound channels, projectiles or projectile in the type of firearm and ammunition (in- fragments, and the presence of fractures and ternal ballistics) used in the shooting as other damage in the animal prior to invasive well as environmental conditions and shoot- action. ing distances (external ballistics), location Firearms evidence collated from both of impact, composition of the target mater- the crime scene and the injured animal can ial and design of the projectile upon impact provide vital information and intelligence (terminal ballistics), for example, may all to those investigating both domestic animal cause variations in the expected severity of and wildlife crimes. The form and extent of damage and lethality. By understanding firearms evidence that may be located at a how these factors may affect wounding, po- crime scene will also vary, depending on tential forensic veterinarians may have an the firearm, ammunition and ballistic vari- increased capacity to interpret the manner ables. Correct handling and recovery of in which injuries have been sustained and such evidence is important for any further provide further information to the forensic analysis requested to be probative in the investigative process. case. Demonstration of the breadth of know- The essential steps in the forensic exam- ledge required to investigate shooting inci- ination and investigation of a shot animal dents may highlight the need for forensic were identified, clearly highlighting the veterinarians to get in contact with subject ­requirement for a logical and methodical experts to provide support prior to and dur- approach supported by extensive documen- ing forensic examinations and any subse- tation. The approach for animals should be quent investigation. By building a strong similar to that conducted on humans and all prosecution case, including corroborative wound ballistics research may be relevant evidence from firearms examiners, investi- for consideration in application to animal gators are more likely to be able to link practice. It is vital for external observations crime series and identify those involved in to be completed before invasive internal the crimes, to ultimately increase the prob- examination commences, and modern non-­ ability of prosecution and conviction in fo- invasive imaging technologies, including rensic cases.

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7.2 Wound Ballistics a wound channel caused by a non-deforming, non-fragmenting rifle bullet. Other types of Johan Schulze projectiles and weapons will cause other effects, and some of these are discussed later in the chapter. A bullet entering a dense medium, like 7.2.1 Introduction a body (or ballistic gelatine), transfers en- ergy to the medium into which it penetrates. A standard rifle projectile like the 308 Win- Wounding mechanisms of stretching, com- chester travels with a velocity of about 800 pression and shearing are initiated. Par- m/s (2625 fps). It takes the projectile less than ticles directly struck by, or close to, the pro- 0.5 ms to penetrate the skin and to create a jectile receive a radial accelerative force wound channel approximately 30 cm (1 ft) causing their temporary displacement per- long (Braathen et al., 2006). The challenge pendicular to the axis along which the pro- for the medical investigator is to understand jectile travels. The effect of this radial dis- the interaction between projectile and body location can be compared with a hard and that takes place within this time frame and radiating punch originating from the wound to estimate how the body responds to this. channel. The centrifugal movement of the He then has to relate this knowledge to his medium lasts until the transmitted energy is investigation, and if possible formulate an spent or is absorbed by elastic tissues (or opinion appropriate to answer the demands gel). At this state, about 2–4 ms after the hit, of the legal system. Interpretations of wound the moving projectile has not only created a patterns which may be appropriate to human wound channel approximately the diameter cases may not be directly transferable to ani- of its calibre, but also an additional larger mal forensic investigation and should be cavity. This cavity, known as the temporary undertaken with caution. wound channel, collapses immediately as the I will first discuss some basic wound bal- of the tissue allows the ­particles to listics by looking at the interaction between a return towards their original position, hereby body and a penetrating projectile. Next, some releasing the stored energy. Depending on specifics not discussed in the first part are the tissue or medium involved, the pulsation highlighted. Finally, essential steps in exam- away from and towards the permanent wound ination of an animal which has been shot will channel continues until all transferred en- be outlined. Readers with a special interest ergy has been translated into friction and in wound ballistics are referred to literature thermal energy. Naturally, this forceful radial including Fackler (1987), Di Maio (1999), pulsation causes anatomical and physiological Brinkmann and Madea (2004), Munro and damage in the living tissue. Munro (2008) and Kneubuehl et al. (2011). Anatomical damage is mainly crushing and tearing. Some tissue close to the pass- ing projectile may also be destroyed by the 7.2.2 Basics of wound ballistics heavy centrifugal acceleration described above. This central core of the wound chan- When investigating injuries caused by a pro- nel, originated by the destruction of tissue jectile, the most important topic is the by the projectile, is called the permanent wound channel caused by the passage of the wound channel. The permanent wound projectile through the body. No two wound channel is encircled by the now relocated channels are alike. Innumerable modifying but previously compressed tissue that had factors make it impossible to accurately pre- circumscribed the temporary wound chan- dict the course or form of a particular wound nel. In contrast to the debris related to that channel. Nevertheless, some important phys- of the permanent wound channel, this latter ical mechanisms are well established and tissue zone has (at least for the meanwhile) knowledge of them is crucial when working maintained viability, despite having been with such injuries. The following describes through forced radial pulsation. 100 R. Bolton-King and J. Schulze

Though viability may be maintained, it of energy transmitted per unit distance (Etr) is obvious that tissue close to the permanent is proportional to the amount of energy the wound channel, having been stretched and projectile has stored (E) and inversely pro- compressed considerably more forcibly, is portional to its sectional density (m/A). The likely to show more severe damage than tis- sectional density is defined as the ratio of sue that is more distant. An area surround- the mass of the bullet (m) to the cross-­ ing the permanent wound channel, named sectional area of contact between bullet and the extravasation zone (Fig. 7.2.1), is char- medium (A). acterized by haemorrhage from lacerated E = E/(m/A) capillaries. The haemorrhages are caused tr more by the stretching of blood vessels, to A bullet travelling perpendicularly to the which they are very vulnerable, than by their plane of contact (tip-first position) has a being torn (Kneubuehl et al., 2011). Bones small cross-sectional area. Hence the amount are far less elastic. The size of a penetration of energy transferred is low compared to the through a flat bone, like a scapula, can be a same bullet having rotated and thus present- very close approximation of the calibre of ing a larger cross-sectional area. the projectile (Karger, 2004). In Fig. 7.2.1 below, the longitudinal The overall form of the wound channel section in the lower part of the figure covers is far from homogenous. Its shape is a direct the total length of the wound channel; the result of the amount of energy transferred two cross-sections in the upper part illus- from the projectile on its path through the trate the profile of the wound channel at the tissue. The more energy that is transmitted, levels of the narrow channel (left) and tem- the harder is the impact and consequently porary cavity (right). the greater the dimensions of the permanent It is difficult to appreciate a detailed im- and temporary wound channels. The amount pression of the extent of a wound channel in

Permanent wound channel

Dead tissue

Heavily damaged tissue, high degree of extravasation Less damaged tissue, extravasation less extensive Stretched but apparently undamaged tissue Unaffected, normal tissue

Fig. 7.2.1. Idealized schematic diagram of a wound channel created by the movement of a non-deforming rifle bullet through tissue (based on Kneubuehl et al. (2011) and Karger (2004)). Firearms and Ballistics 101

a body. Fortunately the physical processes projectile. This effect may be increased con- involved have been visualized by experi- siderably with passage through heteroge- ments, mainly through the study of wound neous tissues. channels in simulants for natural bodies During the last phase of the bullet’s jour- such as ballistic gelatine and soap (Nicholas ney, particularly the last part of the wound and Welsch, 2004). channel, the projectile stabilizes itself, tak- Long and slender rifle bullets striking the ing a position with its longitudinal axis surface perpendicularly can stabilize them- perpendicular to its direction of movement. selves in the tip-first position. The exposure In this phase, the projectile has already of a small cross-sectional area to both transferred much of its embedded energy. permanent and temporary wound channels The kinetic energy transformed in rotation initially being narrow, termed narrow wound is more and more matched, and finally zer- channel. While slowing down, however, the oed, by the resisting medium. The projectile projectile becomes increasingly unstable and moves through the medium, oscillating round starts to tumble as it proceeds. At this point, its centre of mass. If the off-centred posi- the narrow wound channel ends and the tioned tip swings faster forward, it meets a second part of the wound channel begins higher resistance than the opposite base, and (Fig. 7.2.1). The tumbling motion causes pres- vice versa. Thus a self-adjusting mechanism entation of parts of the bullet’s side to the stabilizes the projectile until it comes to rest, medium. The cross-sectional area of contact ending the wound channel. increases momentarily while the mass of the Projectiles may be found with their tail projectile, due to the law of , initially towards their direction of travel. They may ensures the maintenance of its velocity. The also be found slightly withdrawn from the dramatic increase of transferred energy is end of the wound channel. This phenom- accordingly reflected in the dimensions of enon is due to residual negative pressure in the wound channel, which consequently the temporary wound channel that pulls the expands, often considerably. projectile slightly backwards once its for- Having lost stability along the longitu- ward movement has ceased. dinal axis, the projectile rotates around its This description of the formation and transversal axis. In general the rotation will structure of ballistic wound channels is ne- first turn the projectile into a position approxi- cessarily simplified, with the discussion mately 90° to its direction of movement. focusing on a rifle bullet that does not deform, Because of inertia, however, the projectile may break up or fragment. There are many modi- continue to rotate to 180°, or even up to 270°, fying variables that can alter this picture, out of line. At the same time, the bullet is but already certain principles are apparent. decelerated far more markedly than in the Thus, when considering missile wound in- narrow wound channel. juries, we may be able to form conclusions Clearly, more extensive injuries are to or consider different scenarios. be expected from the tumbling of a long, fast-­ travelling rifle projectile than from a shorter • The capacity of a bullet to cause injuries and slower handgun bullet. does not primarily depend on its energy Even in a homogenous medium, the or calibre, but on its ability to transmit axis of the wound channel is not necessarily its energy to the body while travelling straight. When not in tip-first position, the through it. If, for example, no exit hole cross-­sectional area of the bullet is asym- was found and the bullet came to rest in metric. The sum of the withstanding forces the body, the conclusion must be that all affecting the projectile is not solely directed of the energy with which the projectile towards the opposite direction to that of was loaded when reaching the target was the motion of the bullet. Hence the bullet absorbed by the body. If a long narrow receives an additional force vectored per- wound channel, in the absence of dam- pendicularly to its direction of travel. This age to large bones, was demonstrated, force can be strong enough to change consid- one might suspect a long-distance shot. erably the previous direction of travel of the With knowledge of the ammunition 102 R. Bolton-King and J. Schulze

used and the extent of the injuries, such of the bullet is not necessarily welcome in conclusions may be justified. this scenario. Exceptions to these require- • A long narrow wound channel can in- ments may be determined by specific needs. dicate different things: it might mean, Beaver hunters try to avoid large exit wounds for instance, that signs of a temporary to maintain the quality of the fur without cavity will be recognized deeper in the making concessions in terms of animal wel- body than usual, or that the bullet left the fare. This is achieved by the use of splinter body before becoming unstable or de- projectiles designed to fragment after impact formed (see Section 7.2.3.1, ‘Deformation/ (Parker et al., 2006). fragmentation’). It might be as a result Fragmentation, caused either by the of a short bullet fired by a handgun or the bullet’s design or by chance, increases the passage of a full-jacketed rifle bullet overall cross-sectional area, consequently travelling relatively slowly. increasing the volume of the temporary cav- • A prominent temporary wound chamber ity. The mass of the original projectile can be does not necessarily equate to extensive ­reduced considerably (Fackler et al., 1984). injuries – although this is often the case. The fragments are dispersed away from the It merely indicates that a significant axis of the main wound channel. Typically, amount of energy has been transferred the distribution of the fragments is cone- to the body. If the tissue affected has shaped and can be visualized by imaging the potential to cope with stretching techniques. On an X-ray image, the configur- and twisting, the consequences might ation of fragments of a high-velocity rifle pro- be less severe than might otherwise be jectile resembles a snowstorm. The longer expected. penetration depth of larger and heavier frag- ments can be demonstrated, strengthening the evidential value of imaging techniques 7.2.3 Some specifics of wound ballistics regarding the line of departure. However, these findings should be verified; for example, 7.2.3.1 Deformation/fragmentation by necropsy. Steady linear embedding of bullet fragments into tissue does not neces- The deformation of a projectile travelling sarily occur and individual fragments might through a body is not necessarily merely an move from the localization into which they incidental result of being exposed to massive initially settled after the bullet disintegrated. decelerating forces. Hunting bullets, for ex- ‘Loose’ fragments can follow the force of ample, are designed to expand directly after , for instance, and be found at the bot- skin penetration in order to increase the tom of body cavities, often embedded in cross-sectional area and thereby enhance the blood clots, or can be moved due to vascular transfer of energy from projectile to animal. embolization. The secondary translocations In this case, the onset of the temporary cavity of bullet fragments like these must, of course, might start very early. Due to the rapid in- be differentiated and be recorded as such. crease of the cross-sectional area of the de- Furthermore, one should bear in mind that forming bullet at the very beginning of the even slow-travelling projectiles, as shotgun wound channel, the narrow channel can be pellets, can disrupt upon collision with, for short or almost absent. The aim of hunting example, bone (Frank, 1986). bullets is to guarantee the animal’s instant Of course, the penetration depth of frag- death by maximally injuring vital organs. At mented and non-fragmented projectiles cannot the same time it is desirable to create an exit be compared. wound. In case of not succeeding in an in- stant kill, an exit wound bleeding to the out- 7.2.3.2 Entrance and exit wound side is almost a prerequisite for retrieving the injured animal. Hence, despite the ‘mush- Every external inspection of the animal will rooming’ bullet deformation, the aim is to include a close examination of entrance and achieve a high penetration depth by maintain- exit wounds. Though these generally are ing the mass of the projectile, and fragmentation straightforward to distinguish, the assignment Firearms and Ballistics 103

of each wound must be undertaken with (Karger, 2004) or energy dispersive X-ray (Di care. It is the author’s experience that en- Maio, 1999). trance wounds in animals seldom show all At the margins of the entry wound, dif- the features described in standard literature ferent zones merging into each other may be referring to missile wounds in humans. distinguished. The central penetration is This may be due to intrinsic differences, caused by the bullet crushing the skin. A cir- such as differing density of hair coat, or to cular wound results when the angle of im- the fact that close-distance shots are gener- pact was perpendicular to the surface, while ally less frequent in animal cases compared an elliptical wound is formed with a low with human shootings. The skin of dogs, angle of impact. As a consequence of loss of pigs, sheep and goats are said to react most tissue substance the edges of the wound similarly to that of man (Schantz, 1979). cannot readily be adapted. Again, tissue Notwithstanding these possibilities for vari- fragments from the skin are accelerated radi- ation it remains meaningful to take a generic ally outwards from the central contact zone approach to describing the possible com- by the impact of the bullet. After having position of entrance and exit wounds, as the been stretched outwards, the elastic skin re- wounding mechanisms are the same, regard- coils somewhat, so that the entry wound is less of species. smaller than the calibre of the bullet. The The entrance wound can be considered edge and an area only a few millimetres the first part of the wound channel. Its im- wide around the entry wound form a ring of portance lies in being the first point of con- discolouration, due to abrasion and possible tact between the projectile and the body. deposition of gunshot residues. The surface The entrance wound potentially conveys defect is a consequence of the displacement valuable information about the angle of im- of debris from crushed tissue, as well as the pact, characteristics of the bullet and the radial acceleration and stretching of the skin distance between the animal and the muz- caused by the entering bullet. The margin of zle of the weapon. If shot from very close distention, an outer reddened ring that range, singeing of the fur or feathers may be merges into the unaffected skin, is character- present, but due to the splashing and oozing ized by multiple petechial sub-epithelial of blood in the wound area it can be very haemorrhages from lacerated capillaries. difficult to recognize. Again, an asymmetric elliptical shape The entrance wound may be the object of to these changes around the central perfor- special interest regarding the occurrence of ation indicates a low angle of impact, with gunshot residues (GSR). To preserve GSRs, the larger tail pointing towards the shooter. all handling of the wound area must be re- The extent of the damage (as for the exit duced to a minimum, and absolutely no wound) does not convey detailed information cleaning of the wound should be undertaken about the bullet used, but it can indicate the uncritically (Karger, 2004)! Though autolysis, amount of energy transferred at this point in moisture, blood and contamination impede the wound channel. There are many factors GSR analysis, the safest way of submitting an that can modify the configuration of the en- appropriate sample is to excise a larger skin trance wound from that described above, de- area around the entrance wound (Di Maio, pending on different underlying physical 1999). The intact wound with its encircling mechanisms. A large irregular star-shaped skin can then be stored frozen until processed wound might, for example, be seen when further. In living animals, or if the entrance additional forces transmitted by propellant wound needs to remain with the body at nec- gases from a close-range shot affect the wound- ropsy, GSR can be sampled using cotton ing process. buds. On dry wounds, one can use cotton Skin penetration of an exiting bullet buds wetted with distilled water, tape-lifts or involves different mechanisms to those de- use a fine-toothed comb in the hair surround- scribed for the entrance wound. In the major- ing the wound (MacCrehan et al., 2003). ity of cases, the projectile has lost much of Examination for GSRs may be performed by, its energy and exposes a larger cross-sectional for example, scanning microscope area when it hits the skin from the inside. 104 R. Bolton-King and J. Schulze

Consequently, the tissue is not crushed but and the ammunition cause variation of the buckled and stretched until the bullet is re- wound pattern. Generally, the shorter the leased by rupture of the skin. As no tissue distance, the denser will be the injuries of substance is lost, the edges of the irregular-­ the entrance wound. If directly after leaving shaped wound can normally be adapted. If, the barrel, the shot sheaf has not spread ra- meanwhile, the localization of the exit dially, it creates a single prominent circular wound and the large temporary cavity coin- wound. With rising distances and wider cide, loss of substance is obvious. spreading of the shot sheaf, the edge of the wound starts to become undulating (scal- 7.2.3.3 Shotgun loping) or discrete skin perforations caused by individual pellets are seen immediately The wound picture created by shotgun pel- peripheral to the central wound. With still lets is largely determined by the range at which wider spread (or larger distance) the larger the weapon is fired. However, the design of central wound is not present and instead a ammunition used and the barrel characteristics wound field composed of many individual are also important. These three factors deter- pellet perforations is found. mine how densely clustered is the sheaf of pel- The range estimation is based on the lets just before reaching the point of impact. wound pattern as long as a central wound is A pellet sheaf and its ballistic can be apparent, but is based on the dispersion pat- compared with a herd of cattle that is to be tern of the pellets at longer ranges. Correctly driven through a river by cowboys. The cow- scaled documentation of a representative boys determine how densely and how fast wound field, showing all points of impact the animals move when the herd reaches the within that field, is necessary to compare the edge of the river. In a widely spread herd, the pattern in question to the test-shot pattern cows will go separately into the river, thereby fired with the same weapon and ammunition. slowing down, but still in a group that is The resulting range estimation would presup- heading in the same direction. If the herd pose that the test field was within the core stays close together, the first animals entering area of the shot sheaf and that the angle of im- the water will slow down and, being crowded pact was perpendicular (Karger, 2004). and pushed by the adjacent animals, will This may illustrate that detailed state- deviate sideways. ments about shooting distances should only The wound channel of a close-range shot- be made with caution, and should include a gun blast may have a larger diameter than statement of the underlying preconditions. the entrance hole, as the decelerated pellets, Shotgun pellets can be made of many like the cattle from the example above, are different metal alloys, such as lead, steel, deviated outwards by pellets clashing from -- (TBT) and other prin- behind. The light spherical pellets lose energy cipal constituents. A first impression of what quickly and, consequently, the penetration material the shotgun pellet is made of can depth of individual pellets generally declines be achieved by studying the radiological im- rapidly with increasing range. Nevertheless, ages (see Section 7.2.4.1, ‘Before necropsy’). the penetration depth can still be consider- However, true and detailed information is able, markedly disrupting internal organs. based on the recovery of the pellets. Besides The tissue damage of shotgun wounds, es- studying obvious injuries, one should pay pecially close-range wounds, can be exten- attention to possible reactions of the sur- sive. At longer ranges, larger types of shot rounding tissue of each recovered pellet. (size and weight of pellets) produce more Kraabel et al. (1996) observed a consistent serious injuries (Ordog et al., 1988). inflammatory response to steel pellets in It is important to note that the morph- mallard muscle tissue, a reaction possibly ology of the skin wound allows only a rough triggered by corrosion. TBT pellets induced estimation of the shooting range. From comparatively mild inflammatory responses. shooting distances of around 3 m, differing Sterile steel shots surgically implanted characteristics of the barrel of the shotgun into dogs corroded and resulted in severe Firearms and Ballistics 105

inflammatory responses, sometimes compli- ical differences and absolute differences cated by bacterial contamination and foreign-­ can be distinct. The skin of birds is, for in- body reactions (Bartels et al., 1991). stance, generally far thinner than mammal Species-­specific differences in the responses skin (Vollmerhaus et al., 1992), not to mention must be taken into account. Tungsten the vast proportional differences between pellets, for instance, implanted intramuscu- humans and, for example, a budgerigar with larly into rats, induced growth of aggressive, a body weight of 45 g. Wightman et al. (2013) rapidly metastasizing high-grade pleomorphic mounted fresh skin samples of different animal rhabdomyosarcomas in an experimental species on blocks of gelatin to test the effect study (Kalinich et al., 2005). of the skin on the perforation ability of air- Sampling of tissue in a state of inflam- gun pellets; chicken skin had no effect, pig mation or granulation provides an opportun- skin stopped the pellet and cow skin was ity for approximation of age of the process perforated by the pellets. (Schulz, 1990; Wohlsein and Reifinger, 2011). Small calibre and light weight of airgun pellets must not be equated with being in- 7.2.3.4 Airgun nocuous. After discharge, the velocity of the projectiles decreases rapidly and the sec- Though air weapons are commonly con- tional density of the pellets is compara- sidered toys, or at least non-lethal weapons, tively low. There is a need for a high muzzle projectiles from air-powered guns cause in- velocity to counteract these ballistic disad- juries and fatalities (Smith, 1985; Bond vantages. Therefore, unless the anatomical et al., 1996; Campbell-Hewson et al., 1997; structures at the point of impact are very Milroy et al., 1998). These weapons have delicate, the barrel–target distance must be been shown to be dangerous devices for hu- relatively short to cause serious injuries mans and animals, and animals wounded by (Missliwetz, 1987; Kneubuehl et al., 2011). airguns are relatively frequently presented Nevertheless, the transmitted energy can be in veterinary clinics (Cooper and Cooper, 2007; significant enough to fracture the upper arm Anon., 2013). Even pellets fired from a com- bone (Phillips, 1979) or to cause a traumatic paratively low-powered weapon, such as a cervical spinal cord injury (de la Fuente -bearing gun, can penetrate human skin. et al., 2013) in a cat. Indeed, cone-shaped Such an injury is reported by Tsui et al. steel pellets are documented to have pene- (2010). A 15-year-old boy suffered from an trated 1 mm-thick steel plates (Smith, 1985). infected wound caused by a spherical soft The wound ballistics of air weapon pro- airgun pellet, 0.2 g in weight and 6 mm in jectiles follows the mechanisms described diameter, discharged from legal weapons above. However, bruises and other injuries with muzzle energy not greater than 2 . with­out penetration of the skin may be con- Other authors (Phillips, 1979; Sinclair et al., sidered a blunt trauma, rather than a gun- 2006; Cooper and Cooper, 2007; Merck, 2007; shot wound. The pathoanatomical findings Munro and Munro, 2008; de la Fuente et al., may be delicate and may easily remain un- 2013) discuss the ability of airgun pellets, usu- detected, even by the owners of affected ally .177 calibre (4.5 mm) with a law-regulated animals. In a study of injured urban cats maximum muzzle velocity of maximal 7.5 and dogs, as many as 16 out of 19 owners Joule,1 to penetrate human skin or the cor- did not suspect a previous shooting incident nea of the human eye. Penetration depth in when veterinary examination discovered ballistic gel close to 8 cm for 5.5 mm pellets their pet to be carrying a small-calibre pro- fired from 10 m range has been reported by jectile (Keep, 1970). This may be a conse- Ogunc et al. (2013). As in anthropocentric quence of a small-sized entrance wound, a forensics (Bond et al., 1996), veterinarians small calibre of the narrow channel and, in should no longer underestimate the potential many cases, the absence of an exit wound. for life-threatening injury from these weapons. In this context, radiographic examination is As stated above, generalization across very valuable, especially for the detection species is problematic, as both general anatom- of older damage. 106 R. Bolton-King and J. Schulze

The picture of the wound channel at potential evidential value in a living animal necropsy is dominated by the appearance of might be changed by necessary clinical treat- crushed tissue and only moderate bleeding. ment, secondary healing, or the animal’s It should be carefully explored along its ­behaviour (licking of the wound, etc.). Car- total length, especially as some types of air-­ casses change due to autolytic processes. weapon ammunition are embedded in radio- Necropsy, as clinical treatment, is an evidence- lucent components () (Smith, 1985). destroying investigative method. Even when These might be found as a fragment within circumstances suggest a rapid response, one the wound channel and must be preserved should consider spending time on documen- as evidence. tation or preservation of evidence. In any Airgun pellets and remains must, of case, each step must be carefully considered course, be preserved using standard routines. to ensure correct procedure. The secured item can be assigned to the Extensive transfer of information from respective type of ammunition. For the foren- the crime scene prevents misinterpretation sic veterinarian, knowledge of the design of observations made in the clinic or the nec- of the bullet and composition material are ropsy hall. If one does not have the chance necessary to obtain the best possible picture to attend the crime scene oneself, one should of the shooting event. In combination with try to collect as much information as possible anatomical findings – such as location of the by interviewing those involved in the inves- point of impact, penetration depth and type tigation at the scene. Information on who of tissue along the wound path – these ballis- might be the most relevant person(s) to talk tic specifications can help investigators to to might be found on the chain of custody form an impression of, for instance, the range scheme or from the officer with overall of the shot (Missliwetz, 1987). By comparing responsibility for the crime scene. three different types of airgun pellets, Smith Certain general questions need to be ad- (1985) observed distinct differences in pene- dressed in cases involving the use of weapons: tration depth in ballistic gel, and a more recent How many shots were fired and from how British study indicates total penetration depth many weapons? How many victims were there, of gelatin and different animal organs to be receiving how many hits each? Did crime around 10–15 cm (Wightman et al., 2013). scene findings (for example, the blood stain The design of the tip and the material pattern) or the localization of the victims in- from which the pellet is made may not only dicate a connection to the wound pattern? be of value for the investigation, but will Questions specific to each body would have a great influence on the capability of the be: In what position was the body found? projectile to penetrate tissue (Smith, 1985). What kind of injuries were there and were there injury-related marks? An example would be the establishment of consistency between 7.2.4 Essential steps of investigating the body and surface alterations. If an animal a shot animal was lying on the ground when it received a coup de grâce, one could expect the exiting 7.2.4.1 Before necropsy bullet to cause damage on the underlying sur- face. One should be aware of the possibility of The immediate priority in the investigation a residual projectile when removing the body. of a surviving shot animal is to administer The missile could be embedded in the ground appropriate first-aid treatment before pro- or within the fur, or could even have re-entered cessing potential evidence from the animal the body. The latter event could involve an or scene. But even in challenging situations, atypical entrance wound on which the un- a well-structured approach is obligatory for informed veterinary forensic examiner may all forensic work, a sine qua non for the expend unnecessary time and resources at- ­forensic veterinary investigator! The evidence tempting to form an opinion. with which we are working has a constantly Preliminary first impression conclusions changing dynamic character. Alterations of from an adspective on-scene examination Firearms and Ballistics 107

of the body might also initiate other types logists (Flach et al., 2014), resulting in the of forensic investigations. For instance, a development of the specialism named ‘vir- star-shaped wound in the head indicating a topsy’, which has shown to be of high value, short muzzle-to-target distance would prompt especially in wound ballistics. a recommendation to look for backspatter of Information from the crime scene and blood and tissue debris on a suspect’s cloth- from imaging provide a solid foundation when ing or weapon. the forensic veterinarian, whether clinician Whenever bullet wounds or other trauma or pathologist, approaches the investiga- are suspected, the animal should be imaged tion of a shot animal. Nevertheless, all these as soon as possible. Instead of using conven- findings need to be recorded by detailed tional radiography, one might consider a documentation. computer tomographic (CT) examination. In human forensic pathology, imaging techniques 7.2.4.2 The practical approach such as CT, magnetic resonance imaging (MRI) and 3D surface scanners, resulting in After having gone through the routine of three-dimensional imaging, are increasingly the external examination, the next step is to integrated into the investigations, especially focus on the documentation of entrance within trauma diagnostics. Post-mortem CT and exit wounds. For most cases, the line of has been shown to be superior to autopsy departure is of special interest. In almost for depicting fractures and locating project- all cases, it provides a strong indication of iles or foreign objects (Flach et al., 2014). CT position of the weapon in relation to the facilities are nowadays widely available and victim. The entrance and exit wounds are when an animal carcass is sealed in a body the only outer sign of the axis along which bag the requirements of working in an environ- the projectile moved. The axis needs to be ment governed by human health standards measured and documented before the in- can be observed. For detecting non-opaque vasive part of the necropsy, which will items like soft gun pellets, undetectable on alter the normal relative positioning of the X-ray images, ultrasonographic examination body, proceeds. An estimation of the line of is particularly useful (Tsui et al., 2010). ­departure based on the position of the en- The most outstanding advantage implied trance and exit wound alone must be con- using 3D-imaging techniques is the creation sidered as preliminary, since the bullet might of a data set documenting the anatomical pro- have changed its direction within the body portions within a whole body. This is done (see Section 7.2.2, ‘Basics of wound ballis- time-effectively and without the need to ma- tics’). Consequently, statements concerning nipulate the evidence by a destructive this matter should not be made without method (Flach et al., 2014). Structures with verification. deviant density, like a wound channel, can be If the animal was hit by several shots, en- visualized against a variety of denser struc- trance and exit wounds must be aligned. If tures, such as parenchymal organs and mus- there is doubt, then all possible permutations cles. Bullets or bullet fragments can be iden- must be considered and documented. It is tified by their exceptionally high density. The an advantage for the clinicians and patholo- data set can be re-processed and re-­assessed gist over the radiologist that he can easily at any time, enabling accurate measurements. manipulate the animal into a variety of dif- Presentation of complex changes, that court ferent positions to verify a working hypoth- and jury might otherwise be challenged to esis (see Figs 7.2.6 and 7.2.7). Care must be understand by verbal description alone, can taken, however, not to place the animal in an be facilitated. A bullet wound channel, for unnatural body position. This would apply example, can be more clearly demonstrated when attempts are made to trace a wound via the clear narrative of CT images (see Box channel on a suspended body in the necropsy 7.2.1., ‘Illegal shooting of wild grey wolf’). room. The body would be stretched and con- The benefits of 3D imaging has enhanced sequently the tracing risks resulting in an cooperation between radiologists and patho- ­exaggeratedly acute angle of shot. 108 R. Bolton-King and J. Schulze

Box 7.2.1. Illegal shooting of wild grey wolf

By combining the documentation achieved by the use of different methods (necropsy and CT-imaging), strong and illustrative evidence could be presented to the court. In August 2011 the shooting of a grey wolf was reported. A claim of legal self-defence during protec- tion of fenced domestic sheep was made by the defence. Necropsy confirmed that the animal had been shot. The angle of incidence was estimated to be between 0° and 10° from the front-right side. The findings

Fig. 7.2.2. Overview picture from lateral aspect of grey wolf (Lupus lupus), showing the thorax and luminal skeleton.

Continued Firearms and Ballistics 109

Box 7.2.1. Continued.

were in contradiction to the statement of the shooter. The prosecution appraised the angle of incidence as being crucial to the case. Data from the pre-necropsy whole-body computer tomographic examination was processed with the aim of a best possible demonstration and verification of the wound channel. The narrow channel through the back muscles could be visualized and its angle to the spinal column was measured. The result confirmed previous examinations and added valuable material for the courtroom presentation. Figures 7.2.2–7.2.5 are from a video presentation made for courtroom demonstration. In Figs 7.2.2 and 7.2.3, there are fractures with loss of bone substance of the caudal four ribs. The wound is funnel-shaped; there are projectile fragments (bright spots) in the wound area. Each fragment on its own renders imprecise estimation of the axis of travel of the projectile before fragmentation. In Fig. 7.2.4, the entrance wound is seen in the upper part of the picture. Before the bullet fractured the 10th rib, it passed three more cranial ribs and their intercostal . This part of the wound channel is not visible. Figure 7.2.5 shows the narrow channel between the entrance wound and fracture of the 10th rib. The perforation of the entrance wound is slightly out of focus and peripheral muscle layers are likely to be located ‘out of axis’, due to their sliding over the deeper muscles. Thus this outer part of the wound channel is less suitable for the estimation of the angle of incidence and was consequently discounted when the angle between the narrow channel and the spine was measured. The Norwegian Øvre Romerike tingrett (district court) sentenced the shooter to four months’ impris- onment for shooting a grey wolf in claimed self-defence and thereby deliberately violating the right of self-defence.

Fig. 7.2.3. Magnification of the image shown inFig. 7.2.2, now showing caudal thorax and cranial lumbar vertebrae from mainly posterior aspect.

Continued 110 R. Bolton-King and J. Schulze

Box 7.2.1. Continued.

Fig. 7.2.4. Hairless body surface of the same section as in Fig. 7.2.3 and viewed from the same perspective.

Fig. 7.2.5. Visualization of the narrow channel between the entrance wound and fracture of the 10th rib, viewed from a precise anterior aspect. Firearms and Ballistics 111

Figs 7.2.6 and 7.2.7 show a wounded represented by the spinal column of the trunk bear. In Fig. 7.2.7, the probe remains in the is the most appropriate marker for the position same relationship to the wound as that of the animal. Parts that have a high degree of shown in Fig. 7.2.6, but now a possible, freedom such as the tail, the distal extremities near horizontal trajectory of the projectile and the head and neck ­region are consequently that caused the injury can be appreciated, less reliable than the trunk. and approximations of the angle of shot and Second, the narrow channel must be long line of departure can be achieved. enough that its axis can be estimated with a The first part of the wound channel – the sufficient degree of certainty. Finally, one narrow wound channel – potentially yields must succeed in elucidating and documenting the most reliable information regarding the the path of the narrow channel. There are a angle from which the animal was shot. This number of factors which may confound dem- portion of the total wound channel may show onstration of the narrow channel. For instance, the best consistency between the axis on it may not be possible using modern imaging which the projectile travelled before and after techniques to demonstrate a collapsed wound hitting the target. In order to utilize this infor- channel; the true axis of the channel might mation, three conditions must be ensured. not be consistent with the estimated route First, the narrow channel must be local- documented before the body was opened. At ized within a part of the body that justifies necropsy, the carcass may be in a state of ad- conclusions regarding the animal’s position vanced autolysis, softening the tissue around the moment it was shot. Usually there is a the narrow channel. While investigating the demand to comment on the general position wound, extreme care must be taken that the of the animal in relation to the shooter. In instrument is not inadvertently extended be- this context, the longitudinal axis of the body yond the confines of the narrow channel.

Fig. 7.2.6. A brown bear (Ursus arctos) lying in right lateral position enabling a standard left-sided procedure. The probe indicates the longitudinal axis of the wound channel. Entrance wound on the left side of the picture. 112 R. Bolton-King and J. Schulze

Fig. 7.2.7. The same animal as in Fig. 7.2.6, now mounted in a close to natural, ventrodorsal position with vertical forelegs and head and neck bent to the right.

7.2.4.3 Recovery of bullets from the body it should be arranged in a logical manner nearby. If not succeed- Bullets or relevant fragments recovered from ing in localizing the projectile, one can the body must be considered as evidence and re-examine piece by piece by palpation must be routinely preserved using standard or X-ray. techniques. They contain valuable informa- • Bullets must not be handled with metal tion for the case and for the examiner. Submit- forceps or other metallic surgical instru- ted to a ballistic lab more information can be ments in order to avoid alteration of the revealed from further examination. Determin- fragile markings on the surface of the ation of the calibre, distinction between rifle bullet. Sterile single-use forceps are and handgun, the linking of the projectile to established tools for this procedure, an individual weapon or type of weapon, though Di Maio (1999) recommends and/or establishing contact of the bullets with removal of bullets with fingers. Prelim- intermediate target before entering the body, inary measurements can be taken using are examples (Brinkmann and Madea, 2004). a plastic vernier caliper. Some cast-iron rules must be observed • To avoid cross-contamination, clean in the process of missile recovery (Wobeser, instruments must be used for each piece 1996; Walker and Adrian, 2003; Brinkmann of evidence. and Madea, 2004). • Bullets should be washed to remove tissue and blood. The use of fresh run- • Care must be taken not to cut the bullet ning water will be sufficient in most while dissecting in the proximity of the cases but, if special washing proced- projectile. ures need to be followed, temporary • No tissue must be discarded until the pro- storage at −20°C without washing is jectile is recovered. If tissue is removed preferable. Firearms and Ballistics 113

• The recovered bullet should be briefly dissecting along the wound track or by more described by recording general appear- direct ­approach. At all steps of examination, ance, deformation/non-deformation, ap- one should consider the need to take (prelim- proximate calibre, full- or semi-jacketed, inary) tests, such as flaming, assessing magnet- weight, magnetic properties, etc. ism or swabbing, if a local infectious condi- • The dried bullets should be placed in tion is suspected. Definitive examination of wadded packaging (Fig. 7.2.8) and paper recovered projectile(s) or fragments should envelope for storage or submission. be performed at the ballistic lab or at a later • It is sufficient to recover a representative phase of the investigation. sample of pellets from shotgun wounds It is necessary to know about the further (Di Maio, 1999). Redundant pellets may steps of examination regarding each bullet be used for preliminary tests, such as before it is actually removed. Generally, it is a testing for magnetism or flame tests. good practice to wash the projectile under • Fillers (felt wads, plastic cups, plastic fresh running water (Walker and Adrian, crosspieces, etc.) should be handled in 2003). This ensures that the surface of the a similar manner to bullets. bullet is cleaned and tissue and blood cannot harden on it. This procedure is contraindicated Early information about the projectile(s) that if the bullet is to be examined for gunshot are to be recovered is normally based on the residues, however, or for all kinds of foreign assessment of radiographs, pictures or other debris, such as textile fibres, or mineral and images. If the recovered projectile matches biological materials (Walker and Adrian, 2003). the imaged structure, that circumstance To save residues, which may be fragments or should be recorded and in due course marked soft tissue of intermediate targets, the projectile on the picture. It will differ from case to case, must undergo special procedures of washing whether bullet removal is best performed by and filtration (Nichols and Sens, 1990). Pres- ervation of traces is possible even with a bul- let recovered outside the body after completely traversing the body – a so-called ‘through and through’ shot. Karger et al. (1996) succeeded in DNA typing cellular debris sampled from hollow point and full-metal-jacket bullets after full penetration of calves, and achieved successful individualization on the basis of STR loci in three human cases (Karger et al., 1997). It is possible also to perform cyto- logical examinations (Nichols and Sens, 1990; Karger, 2004). It can be expected that the amount of gunshot residue obtainable from semi-­jacketed and hollow-point bullets is lar- ger than from full-jacket projectiles (Karger et al., 1996).

7.2.5 Conclusion

The appearance of wounds caused by differ- ent types of projectiles may range from clear to chaotic. Nevertheless, all modifications are a consequence of the impact of forces falling Fig. 7.2.8. The dried bullets should be placed in under the same laws of physics, a conse- wadded packaging and paper envelope for storage quence of action and reaction. The know- or submission. ledge about what a bullet does to the body 114 R. Bolton-King and J. Schulze

and what the body does to the bullet is working with animals being fired upon. ­crucial for surgeons and pathologists to Hence, being acquainted with the basics of unscramble – at least parts of – the traumatic wound ballistics is indispensable to high-­ modifications they are confronted with when quality forensic work.

Case Study 7.2.1. Cat shot by air rifle by David Bailey (images courtesy of Adele Wharton)

Figures 7.2.9a and 7.2.9b show an overview with the deformed pellet still visible in the and close-up view of a cat that had been shot radiograph. by an air-rifle pellet, with an entry wound It is posited that this animal was lying at rest mid-abdomen. Figs 7.2.9c and 7.2.9d demon­ when it was shot from a cranial direction. The strate massive disruption to the left stifle joint, amount of damage done to the stifle joint sug- gests a close contact discharge.

(a)

(b)

Fig. 7.2.9. The cat shown in (a) to (d) has been shot by an air-rifle pellet. Continued Firearms and Ballistics 115

Case Study 7.2.1. Continued.

(c)

(d)

Fig. 7.2.9. Continued. 116 R. Bolton-King and J. Schulze

Note

1 The specific regulation differs widely between countries. In the UK air weapons are, for the time being, regu- lated by law to below 12 ft lb (16.3 J) for air rifles and below 6 ft lb (8.1 J) for air pistols (Wightman et al., 2013).

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