Module 5 & Tool Marks

Forensic Science Teacher Professional Development Firearms Module MODULE 5A Unit 1 Modern Firearms Development and Manufacture MODULE 5B Unit 2 The Class and Individual Characteristics of Bullets and Cases Unit 3 Microscopic Examination and Comparison of Bullets and Cartridge Cases Unit 4 The Implementation of NIBIN MODULE 5C Unit 5 Estimation of Shooting Distance Unit 6 Gunshot Residues Analysis Unit 7 Serial Number Restoration MODULE 5D Unit 8 The Collection and Preservation of Tool Marks, Tire, and Shoe Impressions Unit 9 The Class and Individual Characteristics of Tool Marks, Tire, and Shoe Impressions Module 5A Introduction to Firearms

Forensic Science Teacher Professional Development

In a gun-related crime, bullets, cartridge cases, and guns (whether discovered at a crime scene or obtained from a suspect) are important items of evidence that a crime scene investigator must collect for laboratory examination and identification. The laboratory testing of ammunition or guns is known as firearms examination or firearms identification. Forensic services of a firearms examination division in a crime laboratory may include • classifying firearms, determining functionality, and explaining the features of the firearms and their proper function; • estimation of shooting distance; • gunshot residue analysis; • serial number restoration; and/or • microscopic examination of fired bullets and cartridges. Microscopic comparisons of fired bullets and cartridges are fundamentally tool mark examinations and comparisons and may include • fired bullets and cartridges collected from crime scenes and test-fired bullets and cartridges from a suspect (in order to establish the linkage of a bullet to a suspected gun, or a cartridge to a suspected firearm); and/or • bullets and cartridges collected from different crime scenes (in order to establish linkages between different crime scenes or establish linkages between firearms). Firearms examiners examine and compare tool marks. Because the task is to compare markings on specific items, firearms examinations and tool mark examinations are usually under the same unit or division in a crime laboratory.

Throughout the module, you may click on the links provided to view additional information.

http://www.cchc.us/Articles/THE%20HISTORY%20OF%20FIREARMs%20&%20Toolmark%20Identification%20--Brownsville%20Excerpt.pdf The following are professional organizations for firearms and tool mark examiners. The Association of Firearms and Tool Mark Examiners (AFTE) allows examiners to obtain their certifications in firearms examination. The Scientific Working Group for Firearms and Tool Marks (SWGGUN) provides a series of consensus guidelines for the firearm and tool mark discipline.

http://www.afte.org/ http://www.swggun.org/ The National Institute of Justice (NIJ) also provides an excellent web resource for firearm and tool mark examiners. To view the NIJ website, you will need to create an account on the website.

http://projects.nfstc.org/firearms/

Unit 1 Modern Firearms Development and Manufacture

Background  A firearm is a device for accelerating a to a high speed, sending it towards a selected target.  The cartridge contains the energy that provides the driving force for the projectile.  A cartridge consists of four basic components: the case, powder, projectile, and .

Rifles, guns, and are common firearms that may be involved in a crime. The first step in a firearm examination is to identify the type of firearm used. Unit 1 Modern Firearms Development and Manufacture

Type of firearms: Classification by firing mechanism

 A single shot fires one round then requires manual ejection of the cartridge casing before another round can be fired.  A semi-automatic fires one bullet then reloads with a fresh cartridge each time the is pulled and released.  An automatic continues to fire until the trigger is released. Unit 1 Modern Firearms Development and Manufacture

Classification by design & purpose

Rifles  A is a firearm designed to be fired from the shoulder, normally having a long barrel.  Rifles can be single shot, semi-automatic, or fully automatic. Unit 1 Modern Firearms Development and Manufacture Handguns  A is a firearm with a defined barrel length limit.  Handguns are classified as single shot, , or semi-automatic . . A single shot firearm must be manually cocked before each shot. . Revolvers have a rotating cylindrical cartridge holder, allowing the weapon to be fired semi-automatically. . Semi-automatic pistols are mechanically analogous to semi-automatic rifles. o A in the grip holds the ammunition. o Empty cartridge cases are automatically ejected. Unit 1 Modern Firearms Development and Manufacture

Examples of handguns

Figure 1 Figure 2 Ruger P series semi-automatic pistols made by Sturm, Ruger & Company A Colt Unit 1 Modern Firearms Development and Manufacture  Shotguns are designed to be fired from the shoulder, having long barrels that are generally not rifled. The barrel is smooth without the grooves and lands.*  shells contain either pellets or a packed into a cartridge along with the powder charge and primer.  The of a shotgun is used as the unit of measurement to express the diameter of the barrel. Therefore, the gauge of a shotgun and diameter of the barrel are directly related.  The gauge is determined from the weight of a solid sphere of that will fit the bore of the firearm. It is expressed as the multiplicative inverse of the sphere's weight as a fraction of a . For example, a 1⁄12th pound ball fits a 12-gauge bore. Thus, there are twelve, 12-gauge balls per pound.

*This terminology will be discussed later in this module. Unit 1 Modern Firearms Development and Manufacture

Shotgun A , or cartridge, consists of five basic components:  The case, including the head  Shot or slug  Wad  Powder charge

 Primer Figure 3 Example of a shotgun shell Unit 1 Modern Firearms Development and Manufacture

Cartridge Components  The case is the container for the other three components of a cartridge.  Powder consists of small disks, cylinders, or balls of known as cellulose nitrate.  The projectile, or bullet, is usually made from lead or copper-coated lead.  The primer consists of a shock-sensitive material. Unit 1 Modern Firearms Development and Manufacture

Figure 4 Diagram of a cartridge http://science.howstuffworks.com/revolver2.html Unit 1 Modern Firearms Development and Manufacture In principle, the firing process (or the cycle of fire) can be separated into several steps:  Feeding  Chambering  Locking  Firing Note that in some firearms,  some of the steps may be  Unlocking simplified or combined.  Extraction  Ejection  Cocking Unit 1 Modern Firearms Development and Manufacture The firing process  The firing pin strikes the primer cup located on the base of the case, compressing the cup and causing the shock-sensitive primer to ignite.  The primer then transfers a spark or flame to the powder charge, located in the body of the case.  The burning powder rapidly gives off heat and gases, and the pressure forces the projectile from the case and down the barrel of the weapon. Unit 1 Modern Firearms Development and Manufacture  Rifling refers to the helical (spiral) grooves cut or impressed into the barrel of a handgun or rifle to cause the exiting projectile to spin and hence have a true and accurate course on leaving the barrel.  The raised areas are known as lands and the depressed areas, grooves.  A spinning projectile has a flatter trajectory and flies a truer path to the target. Unit 1 Modern Firearms Development and Manufacture

Figure 5 Helical groves cut inside a End of Module 5A

Forensic Science Teacher Professional Development