Interpretarea Tehnică a Urmelor Create De Armele De Foc Probleme
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International Journal of Volume 2 Issue 2 / 2012 Criminal Investigation 119-125 TECHNICAL INTERPRETATION OF FIREARMS MARKS PROBLEMS SOLVED BY FORENSIC BALLISTICS Iamandi LUCA, PhD Abstract In terms of forensic science, the interpretation of traces and evidence throughout on-site examination aims primarily to establish the relationship that exists between them and the offense committed. Such an interpretation is aimed at explaining the origin of traces and found objects, the formation mechanism of different types of marks and traces and the relationship that exists between the traces and the evidence (material means) existing in the field of crime. Correct interpretation of the traces found on site can lead to the elucidation of many problems posed by criminal investigation: the nature of the crime committed, the time and place of commission, the operating mode, the number of participants, the actions or inactions of the perpetrator after the crime, etc. Most times forensic ballistics provides solutions both to establish exactly the weapons used in criminal activity and to elucidate the circumstances related to the author, action, participants, victim, etc. All these are related to ballistic expertise. Keywords: firearms, ballistic, technical interpretation Solving problems with ballistic expertise weapon in the legal sense, the Judicial ballistic expertise, as part category that fits the gun; of forensics, shall be performed in a - What is the type, model and caliber of specialized laboratory1. the firearm; which is the serial number The request for expertise shall be of the fire arm; forwarded to the institution where the When the inscriptions stamped on laboratory functions and not directly to a the gun have been removed, chemical person. electrochemical or ferromagnetic methods The head of the institution will should be considered to reveal them. nominate the specialist who will perform - status of the firearm. the examination, in relation to the nature b) On firearm use use: and the complexity of the work and the - evidence to prove recent firing; work load of each subordinated expert2. - possibilities to fire a faulty weapon; The questions that the experts must - possibilities to fire without pulling the answer should only cover very specific trigger; aspects, and can not extend to matters - the weapon’s operating status, caliber outside their competence (legal and effectiveness of a crafted weapon; classification, for example). - existance of traces of additional In case of infringements of the factors of firing on the gun barrel; weapons and ammunition laws, the - distance and direction of the shot, following main issues can be cleared by possibly the victim’s and the drawer’s ballistic legal expertise: positions; a) On weapon: - if a shot hole is the entry or the exit; - if the device under examination is a http://www.ijci.eu eISSN: 2247-0271 119 TECHNICAL INTERPRETATION OF FIREARMS MARKS PROBLEMS SOLVED BY FORENSIC BALLISTICS - if the victim was hit by a ricochet or After the shooting, so after leaving direct fire; the barrel, the bullet goes back to its - type, model and brand of the weapon original size or suffers some longitudinal that was shot after marks on the tubes deformation. or on the bullets under consideration; The barrel interior construction is - if tubes or bullets from the crime precisely indicated by the rifling grooves scene were fired or not by the gun marks on the bullet. provided for test firing3; The rifling characteristics (the - if the gun provided for test firing has distance between the grooves) and the been used for other attacks. twist rate provide information on the type, c) On ammunition: brand and model of the firearm. - series, size, model, type of bullet and For example, if on the bullet there tube; are no transversal marks and there are only - qualitative state of the shell; longitudinal marks, either there was a gun - if they were made industrially or with a strongly corroded5 barrel, or handicrafted; unnapropriate bullets have been used. - if the shot ammunition shows Thus on site can be found similarities to the comparison model;4 deformed shells or bullets or even broken d) On the silencer: ones. - if a silencer was attached to the gun; This can be caused either by use of - the technical features of the silencer; a firearm with the barrel cut off or a - if it was made industrially or normal gun but when the bullet hit an handicrafted. obstacle and reached the target via Ballistic expertise can also solve ricochet. other issues i.e. acoustic examinations In case of shells found on site, their (examination of the sound traces of the size, format and weigh will indicate the shot, of the arming and of the percussion). type of the used firearm: rifle, pistol or revolver. Establishing the type, model and brand Note that the shell, its neck and its of the weapon that was fired internal diameter always reveal the firearm caliber. The bullets and the shells found on At the outbreak of fire, due to gas site can supply valuable details. pressure, the cartridge case and its neck Thus, the bullet diameter - in the thickest are slightly expanded, causing a diameter part – usually indicates the weapon’s increase. caliber. If expansion is more pronounced The explanation is that the bullet, and the neck is more or less cracked it can the cartridge component for a particular be appreciated that a smaller caliber bullet weapon, has a size of 0.2 - 0.5 mm larger was used. than pipe size. The following table shows the For this reason it can not be bullets and cartridges cases characteristics introduced into a firearm neither before that can help determine the make and nor after the shot. caliber of firearms. 120 International Journal of Criminal Investigation, 2, 2, 119-125 Iamandi LUCA Nr. Cartridge Caliber Length ( mm) Weight (grams) Crt (mm) cartridge bullet Case cartridge bullet case 10,2- 1 For pistol 7,62 34,7 14 24,5 5,45-6,7 1,57-1,7 11,1 Model 1933 2 Standard for 6,35 23,0 12,6 13,7 5,3 3,3 2,0 Browni ng 3 Standard for 9scurt 24,7 11,5 17,4 9,5 6,0 3,25 Browni ng 4 Parabbelum 7,65 29,5 15,0 21,5 10,5 6,0 4,14 5 Parabellum 9 29,5 15,0 19,0 12,5 8,0 3,15 6 Label for 8 36,5 26,5 15,7 12,0 7,8 4,0 revolver 7 Colt,md 1911 11,43 32,4 16,3 22,8 19,0 12,9 5,8 Rifle with 8 7,62 77,16 28,6 53,0 21,75 9,6 9-11 light bullet 1908 Russia When the specialist or the expert is - The barrel pipe thickness; presented with a less known firearm it - The number, the orientation and the could be difficult to establish its make, size of the grooves. model and type. It can be concluded that both the Firstly he will examine the construction of the gun parts which leave inscriptions and the signs of the producer. tool marks on the cartridge case and their Along with the gun serial number the dimensions, including their positioning, firearms may present many inscriptions can lead – in most cases - to accurately with various meanings, for example the establish the fire gun model. firearm name, the caliber, the manufacturer’s name. Functioning status of the fire gun Secondly, especially when the above mentioned inscriptions are missing, The issue of establishing the state he will proceed to establish the technical of operation of the weapon comes up when and constructive features of the firearm. the person who fired claims certain defects The technical details of any firearm of the firearm. consist of: Given that research of this kind is - Total length; very difficult, forensic practice - Weight with and without cartridges; recommends that the examination of the - The length of the bore; gun is run in a certain order, using every http://www.ijci.eu eISSN: 2247-0271 121 TECHNICAL INTERPRETATION OF FIREARMS MARKS PROBLEMS SOLVED BY FORENSIC BALLISTICS weapon’s instructions provided for grip the breech is pulled back and then examination. released. One then checks if the breech The firearm should be examined came back to the initial position and if the mounted as well as dismounted. cartridge was pushed into its chamber7. Examination of mounted firearms When the hammer is blocked with is performed to determine the state of the safety catch and the trigger is pulled, maintenance of parts and their functioning. the trigger must not move back and the It is recommended that a breech should not move. roentgenography or a gammagraphy is The last check is aimed at performed before the gun is dismantled to establishing whether the firing avoid accidents, in case the firearm is mechanisms work well. Thus we check if, loaded or blocked. when pressing the trigger the cock is easily The photography will indicate the released from the ‘armed’ position. When state and the way that the gun parts are no more pressure is applied on it, the combined. It is necessary to establish the trigger comes back to the initial position. amount of pressure that needs to be Examination of dismantled applied on the trigger to determine the firearms. Each component part will be onset of the lock. This is determined using examined separately. Firstly we check if a dynamometer or a weight hanging on the the parts have the same serial number. The gun’s trigger. The lowest degree of barrel examination – after it is wiped with pressure required for a well functioning clean cloth – is aimed at establishing gun should not be below the minimum channel defects: shown in the tables or indicated by the - missing chips, indenture, pores, bigger manufacturer.