Forensic Sci Analysis & Lab
Forensic Sci Analysis & Lab FRSC 4253
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This 10 page Class Notes was uploaded by Alessia Huels on Thursday October 22, 2015. The Class Notes belongs to FRSC 4253 at University of Central Oklahoma taught by Dwight Adams in Fall. Since its upload, it has received 33 views. For similar materials see /class/227707/frsc-4253-university-of-central-oklahoma in Forensic Science at University of Central Oklahoma.
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Date Created: 10/22/15
Cusack 1 01102011 The Anatomy of Firearms 0 Purpose 0 The purpose of this module is to familiarize yourself with the anatomy of rearms and the most common firearm types 0 Objectives 0 The earliest known firearm ignition systems and their anatomy and shortfalls o 3 popular ignition systems that ultimately provided the greatest milestones in weapon and ammunition development 0 Characteristics of ri ed barrels o Firearm nomenclature o The most common firearm types used today and their anatomy 0 Brief history 0 Modern firearms are manufactured in a variety of shapes and sizes to fit multiple purposes 0 Today there are vast numbers and a staggering assortment of models 0 In today s society practically any type of gun can be found Uses vary by youth gangs persons involved in drug trafficking paramilitary survivalists and even what we would considers ordinary citizens o The earliest form of a firearm was simply a small cannon hand cannon 0 These weapons were likely used as psychological deterrents more than anything else 0 Originally hunting and intimidation o 3 firearm ignition types I Matchlock I Wheel Lock I Flintlock o EXpensisve 0 Early ignition systems 0 httpwwwhuntered 39 coursech5 know vour 39 39 J htm photos I Rust causes M16 to jam 0 Inability to oil gun o Matchlock and Wheel lock systems I Matchlock 0 Pan 0 Pan cover 0 Slow match 0 You actually have to light 0 Unable to stay lit if wet or moist I Wheel lock 0 Pan 0 Pan cover 0 Pyrite Cusack 2 o Creates a spark o Cock or doghead o Springpowered wheel I Flintlock 7 rst time we see people say cock the hammer 0 Flint o Frizzen 0 Causes spark 0 Lock plate 0 Pan 0 percussion lock 0 cock 0 Cap 0 Nipple I Combustion and hot gases I 3 popular systems that were breakthroughs in the history of rearms were 0 The pin re system bad 0 Primer cup 0 Firing pin 0 Cartridge case 0 projectile o The rim re system 22 caliber short long long ri e common 0 Hammer with ring pin 0 Primer o Cartridge case 0 projectile o The center re system 7 know this drawing 7 one of most prominent designs 0 Firing pin 0 Priming compound 0 Primer cup 0 Cartridge case 0 Flash hole 0 What is normal versus abnormal o More and more airsoft pistols look like real things I Not taped no neon sights 0 Regular consumer would not know that it isn t a real pistol o Ruger Mark III I 22 caliber I Smaller than palm of hand ts on a keychain I Revolver 011211 0 Smooth bore weapons 0 Made of wrought iron or steel Cusack 3 I Heavy rusting 0 Black powder I Stuck to barrel walls I Turned to sulfur like substance 0 Load ball shaped and spherical ammunition 0 Pack and re 0 Ri ed Barrels o The most important aspect of rearm and tool mark examination revolves around the identi cation of characteristics 0 There are two speci c types of characteristics associated with ri ed barrels and ammunition components I Class characteristics 0 Predetermined manufactured features 0 Chambered for what caliber bullet 0 Length of barrel 0 Nominal diameter of the bore Provide a means to quickly rule out certain sources and narrow down to a smaller group of possible sources I Individual characteristics 0 Imperfections or irregularities produced accidently during manufacture or caused by use abuse corrosion rust or damage 0 Use I Multiple rings I Not cleaning 0 Abuse Putting something down barrel that scratches ti o Are unique and original to any and all tools 0 When a bullet is red through a ri ed barrel the lands of the ri ing cut into the sides of the bullet creating depressions called Land Engraved Areas LEAs the nondepressed regions on the bullet are called Groove Engraved Areas GEAs I Ri e barrel land makes a groove on a bullet A groove inside a barrel creates a bullet land Have an inverse relationship between lands and grooves bullets and barrels I This is what NIBlN measures for 0 While there are numerous methods of barrel ri ing the two most common types are Conventional and Polygonal I Conventional 0 Cut ri ing 0 Will always have de ned shoulders 0 Bullet red will always have de ned shoulders 0 distinct I Polygonal o Instrument inserted into barrel and barrel is beat to t that pattern 0 Smooth 0 Looks like it just slid down the barrel Cusack 4 o Darkening slippage 0 Burns as it slides down the bullet gases escape on edges of the ri ing I Masks typical characteristics I Hard to identify 0 Masks individual characteristics on bullets o Cartridge cases have lots of characteristics I Mostly seen in handguns and semiautomatic pistols o Reasonably priced 0 Law enforcement uses 0 Desert Eagles 0 HNKs I High end semiautomatic pistol o Firearms terminology o The Association of Firearms and Toolmark Examiners AF TE created a glossary of terms 1977 that was to be used as reference guide for terms commonly used in the discipline However over time contributions have been so extensive for the purposes of this course we will only examine those necessary 0 Ri ing I Term given to spiral grooves cut into the bore of a barrel 0 Stabilizes a bullet in ight o Improves trajectory o Caters to higher velocity I Groove Diameter 0 Photo Precision Forensic Testing 0 Groove at top to groove at bottom I Bore Diameter 0 From land to land interior portion of bore 0 Lands I Always have equal numbers of lands and grooves I Twist left or right 0 Land ows over your right shoulder 0 Right hand twist 0 Land ows over your left shoulder 0 Left hand twist o Grooves I Always have equal numbers of lands and grooves o Caliber I Nominal diameter of the bore within a firearm in inches ie 357 I In regards to ammunition caliber refers to nominal bullet diameter without the decimal included I European made 0 9 mm o 9 x 19 inches in US 355 inches Cusack 5 0 Action I The working mechanism of a rearm I May be broken down into action types ie bolt automatic lever o Projectile Bullet I An object propelled by force of rapid burning gases or other means I Bullet o A nonspherical projectile for use in a ri ed barrel 0 Cartridge Case I The container that holds all components which make up a live round of ammunition o Propellant I The chemical composition within a cartridge case that produces combustion and gases propelling the projectile 0 Primer I The ignition component of a cartridge case 0 Recoil I Note Every rearm has recoil For every action there is an equal or similar reaction Is the effect mechanism that creates a reaction due to pressure and force within a firearm o Often referred to as bite or kick o ie the average pressure in a 45 caliber pistol is around 14000 pounds per square inch 0 meaning when the pistol is red there is a pressure over one ton pushing the bullet down and out the barrel while at the same time pushing the gun back towards the shooter o Firearm Types 0 Are pellet guns BB guns air soft pistols or paintball guns considered rearms No They don t use combustion Legally is a firearm inthis course it is not a rearm I Know the code word for word on test I The Federal Statue Title 18 United States Code Section 9211a113 o 13 the term rearm means A any weapon including a started gun which will or is designed to or mav readily be converted to expel a projectile by the action of the explosive39 E the frame or receiver of anv such weapon C anv firearm muffler 0r firearm silencer or 1D any destructive device Such term does not include an antigue rearm o Muffler or silence I This includes a potato o Antiques I Have to be manually lit 0 There are four types of rearms I Pistol 0 Background 0 Earliest known was the Colt 1911A Cusack 6 o Advantage I Utilizes its recoil to eject load and cock the hammer o Disadvantage I More complicated design requires more practice I Barrel lengths are usually limited 0 Longer barrel means more accuracy 0 Example revolver just have to line up sight 0 Barrel moves in a pistol 0 Not lock breach 0 Pull slide back and it is loosened I Only tted into the frame I Internal hammer drops 0 Action types consist of o Semiautomatic I Autoloading 0 Fires loads extracts ejects repeats FLEER o Recycles very fastly I All semiautomatic weapons utilize an additional pull of the trigger perform the operating cycle 0 Double Action Only DAO I Single pull res loads extracts ejects repeats FLEER 0 Heavy Trigger Full 0 Load magazine single pull of trigger cocks the hammer 0 Safe Action Single Action Semiautomatic I Termed by Glock I Safety mechanisms 0 Three stage trigger o If you drop the gun or put finger on trigger but don t push d tip down it wont fire 0 Must have finger fully on trigger 0 Internal firing pin block 0 Wont let hammer fall forward 0 Drop safety 0 Keeps firing pin from falling forward 0 Has a notch I Safest working pistol for those that ca1ry gun cocked and loaded 0 Parts 0 Genitron com 0 Slide Cusack 7 0 Safety 0 Hammer 0 Frame I Only portion that contains the serial number I Considered a rearm in itself I Does not include slide connected to the body 0 Trigger guard 0 Slide release 0 Trigger 0 grips I Revolver 0 Background 0 Advantages I Simple design I Reliable I Reasonable price I Tend to be more accurate 0 Long barrel 0 Disadvantages I Limited to six shots I Slow reload I Trigger pull is greater 0 Firearm having multiple chambers configured around an axis 0 Utilize the same discharge mechanism or action to successfully discharge 0 Actions 0 Single action I Requires manual cocking of the external hammer before sufficient pressure releases the firing mechanism 0 Benefit 0 Lighter trigger pull 0 Releases trigger to the rear after manual cock not the same thing as a hair trigger 7 not standard from manufacturer 7 manipulated 0 Double action I An action in which a single pull of the trigger cocks and releases the external hammer o Disadvantage o Heavier trigger pull 0 Parts 0 Genitron com 0 Cylinder stop notches 0 Frame Cusack 8 0 Cylinder release 0 Hammer 0 Cylinder 0 Barrel 0 Ejector rod 0 Trigger guard o Trigger 0 grips I Shotgun 0 Background 0 Similar in appearance to ri es but the barrel is much larger 0 Do not have ri ing I Smooth bore weapons 0 Advantage I Ability to utilize different forms of ammunition o ie slug pellets buck shot 0 a long aimbig bore rearm consisting of a receiver stock and barrel Combinations or frames may be con gures as overunder double barrel or hinged frame 0 Actions 0 May vary depending on style of shotgun however actions are similar to those used in ri es I ie Autoloading single action and pumpslide action 0 Pump action most common style and most commonly preferred 0 Pumpslide action I Requiring the manual cycling of a slide located in front of the receiver to load operate the firing mechanism extract and eject the fired cartridge 0 Parts 0 Stock 0 Safety 0 Framereceiver o Ejection port 0 Magazine 0 Foreend o muzzle I Ri e 0 Background 0 Differ in length when compared to other handguns primarily in barrel length and the presence of a butt stock 0 Most often utilized for hunting and military 0 Advantage I Much more accurate and powerful O 0 Action 0 W E 00000000 0 Cusack 9 Considered a long aim rearm consisting of a barrel and stock which may contain one of many actions While there are multiple action types ie single action bolt action semiautomatic and pump action the most commonly known are the bolt action and the lever action ri es I Bolt action 0 Requires manual loading manual cycling and manual bolt engagement in order to operate the ring mechanism I Lever action 0 Requires the manual operation of an external lever below the receiver in order to operate the ring mechanism Stock Bolt handle Safety Trigger guard Trigger Magazine oor plate Bolt Muzzle Barrel 0 Submissions Evidence Retrieval and Transfers 0 First steps always include evidence collection preservation and documentation 0 It is pertinent that all evidence transfer documentation is recorded and kept on hand in order to provide a proper chain of custody I Submiss1ons 0 Property management 0 May deliver the evidence to the respected laboratory and have personnel sign it in and out 0 Evidence BarCoding 0 Falls under the chain of custody tracking method and may or may not be utilized by an agency 0 Chain of Custody Logs O 0 Numerous can be broad or more speci c Speci city is always better I Evidence Retrieval 0 Evidence once obtained by the examiner should be logged or booked into the laboratories evidence log then properly stored until examined I Evidence Transfer 0 Once evidence has been examined and resealed proper paperwork to complete the chain of custody log should be lled out Cusack 10 o The evidence may then be transferred to another unit for examination or back to the property management unit for storage
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