Lecture 2 - FA1 - Firearms Analysis (2024)2.pdf

FA1 – Forensic Firearms Analysis FSCI 3010u Fall 2024 1 Firearms – Assigned Reading Lecture notes Fundamental of Forensic Science (Houck & Siegal): Chapter 21 pp 531 to 541 Posted PDFs specific to types of firearms and ammunition NIST/OSAC SWGGUN links Mandatory: know the purpose and role of these organizations Recommended: become familiar with what has already been published 2 November 22, 1963 https://ww w.youtube.c om/watch? v=Zmz4lz6l 8Fs 3 http://www.washingtonpost.com/w p-srv/special/national/jfk-50th- anniversary/ https://www.jfk.org/exhibition/ 4 5 A Brief Review 6 What is Forensic Science? This Photo by Unknown Author is licensed under CC BY-NC-ND What is Science? 7 8 To be accepted in court… WE WILL COVER THE DAUBERT STANDARDS LATER IN THE SEMESTER THE THEORY MUST BE VALIDATED THROUGH THE TESTING OF THE THE THEORY MUST BE FUNDAMENTAL PROPOSITIONS TESTABLE. UPON WHICH THE SCIENCE IS BASED. 9 10 NAS 2009 Report National Academy of Sciences Report put in serious question the state of forensic sciences Much has changed since then! 11 Establishing Guidelines Scientific Working Groups (SWG) developed standards for best practices Previously Started by the FBI Working groups made up of scientists from around North America https://www.nist.gov/forensic-science/interdisciplinary- topics/working-groups/legacy-scientific-working-groups NIST/OSACs Today NIST – National Institute of Standards and Technology OSAC – Organization of Scientific Area Committees Government based, set-up by President of the USA 12 https://www.nist.gov/forensic-science 13 14 Physics/Pattern Interpretation Scientific Area Committee The Firearms & Toolmarks Subcommittee focuses on standards and guidelines related to the examination of firearm and toolmark evidence. This includes the comparison of microscopic toolmarks on bullets, cartridge cases, and other ammunition components and may also include firearm function testing, serial number restoration, muzzle-to-object distance determination, tools, and toolmarks. Bloodstain Pattern Analysis Forensic Document Examination Firearms & Toolmarks Friction Ridge Footwear & Tire https://www.nist.gov/topics/organization-scientific-area-committees-forensic-science/physicspattern-interpretation 15 OSAC progress includes (drafts) Validation Quality system Terminology list standards standards Case notes, report Collection and And much, much writing, expert storage more testimony 16 SWGGUN Remember slide 12? Scientific Working Group for Firearms & Toolmarks (SWGGUN) Provide working guidelines Provide training guidelines, etc. Discuss analytic methods Monitor research and technology Exchange ideas and other information in the forensic firearm and toolmark discipline The Admissibility Resource Kit (SWGGUN ARK) https://afte.org/resources/swggun-ark 17 Firearms & Ammunition 18 Introduction Individualizing characteristics transferred to bullets and Firearms examination is cartridge cases complex, technical, and Ammunition Analysis (GSR, May include shooting detailed work reconstruction Muzzle to target and the use of distance) ballistics Firearm Ballistics is the study of an Science object in flight and is under the Examining tool domain of physics marks requires Operation and understanding of performance how the tools themselves are made and used Forensic firearms science is Manufacture the study of firearms 19 Examiners should have a broad knowledge and familiarity with various types, makes, models, and styles of firearms New products and older models and the history of Types of Firearms manufacturers and their products Sporting, Hunting, and Outdoor Trade Show and Conference (SHOT Show) is good source of information 20 Firearms: TWO TYPES SHOULDER FIREARMS HANDGUNS Rifles Revolvers Shotguns Pistols Machine/military guns 21 Revolvers Ammo is fed into firing chamber through revolving cylinder To load/unload, cylinder swings out or can be released Cylinder revolves by cocking the hammer (or pulling the trigger) https://www.youtube.com/watch?v=TXliIJ_66F Q 22 Semi-automatic Ammo fed by spring-loaded magazine Fires one bullet for each trigger pull https://www.youtube.com/watch?v=rJMXXuGhIN E 23 The Curious Case of Squib Rounds An interesting side note! Magnum revolver blocked with a bullet – multiple rounds fired to attempt to remove blockage Two main causes of squib rounds: Inadequate powder put into the load – the use of reloaded ammunition to save money No gunpowder in the load – primer can send the bullet just far enough to block In Movies and TV… the barrel Very dangerous! Gases and debris could fly back towards the shooter Gun could explode! 24 Rifles Repeating One bullet fired for each pull of trigger Must expel cartridge, cock & reload from a magazine Bolt action or lever Semi-automatic Use energy of fired ammo to expel empty cartridge, cock & reload Automatic Machine gun https://www.youtube.com/watch?v=QKa4OQBejKQ 25 Shotguns Like a rifle, but with a smooth bore Fires pellets – also called “shot” Fires single projectiles – called “slugs” 26 Shotguns Barrel may be constricted to “choke” the pellets Diameter = “gauge” How many lead balls with same diameter of barrel would weight one pound? That’s the gauge 27 Rifling 28 Common Rifling Methods Broach rifling Button Rifling ◦ The use of a long, hardened steel rod ◦ Most common method with several cutting rings spaced down ◦ A button is a very hard steel plug that is the rod forced down an unrifled barrel ◦ Known as ‘gang broaches’ ◦ The grooves are then formed in the ◦ Each successive cutting ring is slightly barrel under very high pressure larger in diameter ◦ The pressure created to form the rifling ◦ The cutting rings have gaps evenly in the barrel hardens and polishes the spaced around them to allow for the inside of the barrel lands ◦ The rod is twisted as it is pulled through the barrel and this forms the spiral to the rifling pattern 29 Look down the muzzle: 30 Resulting impressions 31 Polygonal Rifling Impressions A by-product of hammer forging More rounded edges (compared to squared off edges of cut rifling) Solid steel mandrel is produced with desired rifling shape and inserted into blank barrel Outside of barrel is hammered Most common patterns are 6/right and 8/right Glock, Steyr, IMI, SIG Sauer, etc. 32 Bore diameter – a circle which touches tops of lands Note: “Caliber” – used to mean bore diameter – it really is an approximation 33 Ammunition Ammunition is what a firearm fires! For handguns/rifles For shotguns Known as a ‘bullet’ or Known as a ‘shell’ ‘cartridge’ Similar to bullet ammo, but Contains one or more of: pellets/shot need to be held Single solid projectile together Propellant (fuel) Wadding between pellets & Primer (igniter of the fuel) propellant Cartridge case 34 Bullets Bullets can be classified as one of three main types: 1. Lead/lead alloy Hardened lead with minute amounts of other metals 2. Fully jacketed Lead core wrapped in copper/nickel or steel 3. Semi-jacketed Metal jacket only partially covering – nose exposed Eg. Hollow point cartridge 35 Bullet/Cartridge 36 Shell 37 PROPELLANT PRIMER Smokeless powder, ignited by Small metal cup contains primer percussion-sensitive material Nitrocellulose + stabilizers Struck by firing pin Includes Lead, Antimony, Barium 38 What happens when ammunition is discharged? Hammer strikes primer cap Centre fire or rim fire Primer explodes Propellant ignites, generates hot gases Bullet pushed out of cartridge case https://www.youtube.com/watch?v=RWpE7ZltIx Bullet travels down barrel, 8 scratched by L/G etc. 39 Next steps – forensic analysis Striations Headstamps/Cartridge case characteristics Firing pin impressions Measurements Eg. Bullet weight/caliber Cartridge extraction marks Wounds/damage Cartridge ejection marks Trajectory/ballistics Breech marks Databases Plume (distance measurements) Etc.!!! 40 Have a Great Weekend! 41

Lecture 2 - FA1 - Firearms Analysis (2024)2.pdf

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