Firearms, Tool Marks, and Other Impressions Objectives: Describe techniques for rifling a barrel. List the class and individual characteristics of bullets and cartridge cases. Explain the utilization of the comparison microscope for the comparison of bullets and cartridge cases. Distinguish caliber from gauge. Created by C. Ippolito April 2008 12/3/2018

Firearms Identification concerned with determining whether a bullet or cartridge was fired by a particular weapon bullet  gun structural variations irregularities scratches & nicks breaks & wear more than bullet comparisons weapons operation restore obliterated serial numbers detect & characterize GSR determine muzzle-to-target distance Even 4 4/3 Created by C. Ippolito April 2008 12/3/2018

Gun Barrel Manufacture made from solid bar hollowed by drill random marks left followed by rifling grooves on inner surface “twist” bullet for straighter, more accurate path rifling methods hook cutters – rotated – forms spiral groove – 1 at a time broach cutter – concentric rings – simultaneous cuts all button process – metal plug compresses sides mandrel process – barrel hammer from outside down Created by C. Ippolito April 2008 12/3/2018

Gun Barrel Terms Bore Rifling Groove Land Caliber the cavity inside the barrel Rifling spiral grooves in bore spins projectile Groove cut/low-lying parts of rifled bore Land uncut/raised parts of rifled bore Caliber diameter of the bore hundredths of an inch (.22) millimeters (9mm) Created by C. Ippolito April 2008 12/3/2018

Bullet Markings Class Characteristics lands grooves twist direction General Rifling Characteristic File FBI data base of class characteristics Individual Characteristics striations fine lines caused minute imperfections on cutters steel chips from cutters Comparison Microscope tool used to compare bullets Created by C. Ippolito April 2008 12/3/2018

Shotgun Barrel smooth bore gauge groove would spread pellets diameter of barrel # of lead balls with diameter = to bore of barrel that would weigh 1 lb Created by C. Ippolito April 2008 12/3/2018

Comparison of Cartridge/Shotgun Shell Created by C. Ippolito April 2008 12/3/2018

Cartridge/Shell Markings Breechblock rear part of barrel marks base of cartridge/shell Firing Pin strike mark on base of cartridge/shell Ejector/Extractor mechanism that removes cartridge/shell from chamber leaves unique striations Created by C. Ippolito April 2008 12/3/2018

Firearms, Tool Marks, and Other Impressions Objectives: Explain the NIBIN data test system. Explain the procedure for determining at what distance from a target a weapon was fired. Describe the laboratory tests utilized for determining whether an individual has fired a weapon. Emphasize the limitations of the present techniques. Explain why it may be possible to restore an obliterated serial number. Created by C. Ippolito April 2008 12/3/2018

Automated Firearm Search Systems DRUGFIRE (FBI) unique markings on cartridge cases microscope images captured and digitalized Integrated Ballistic Identification System (ATF) Bulletproof bullet analyzing module Brasscatcher cartridge analyzing module National Integrated Ballistic Identification System 1999 the two systems combined Created by C. Ippolito April 2008 12/3/2018

Gunpowder Residues Distance determination Handguns and Rifles distribution of powder/pellets calculate firearm distance from target Handguns and Rifles 1” or less heavy smoke stains loose fibers/melted fibers star-shaped tear surrounded by smoke 12”-18” halo of smoke stain 25”-36” scattered gunpowder particles ball powder cartridges can extend to 6’-8’ > 3’ bullet wipe carbon, dirt, lubricant which wipes off surface of bullet Created by C. Ippolito April 2008 12/3/2018

GSR Patterns Created by C. Ippolito April 2008 12/3/2018

GSR Patterns 3” 9” 15” 21” Greiss test Sodium rhodizonate Test shows nitrites Sodium rhodizonate Test turns lead particles pink then violet Created by C. Ippolito April 2008 12/3/2018

Primer Residues Dermal Nitrate Test Primer Test paraffin wax treated w/diphenylamine blue color w/nitrates Primer Test looks for: lead styphate barium nitrate antimony sulfate SEM Testing Neutron Activation Analysis Atomic Absorptive Spectrophotometry Created by C. Ippolito April 2008 12/3/2018

Serial Number Restoration detects strain in metal crystals can be “re-etched” HCl + copper chloride + water for steel Created by C. Ippolito April 2008 12/3/2018

Firearms, Tool Marks, and Other Impressions Objectives: List procedures for the proper collection and preservation of firearm evidence. Explain how a suspect tool is compared to a tool mark. Explain the forensic significance of class and individual characteristics to the comparison of impressions. List some common field reagents used to enhance bloody footprints. Created by C. Ippolito April 2008 12/3/2018

Collection & Preservation of Firearms Safety – unload any ammo note hammer/safety position note location of fired/unfired ammo Revolver note chamber position note cartridge/casing in chamber w/position each round in own box Automatic remove magazine – test for prints Water recovery ship weapon with water covering weapon Created by C. Ippolito April 2008 12/3/2018

Collection and Preservation of Ammo Must save class/individual markings free bullets by breaking away material use only plastic tools scribe with initials leave trace materials on bullet paint, fibers, etc. Created by C. Ippolito April 2008 12/3/2018

Tool Marks indented impressions class characteristic all tools show microscopic irregularities from their manufacturing indented impressions individual characteristics microscopic irregularities from damage and wear Created by C. Ippolito April 2008 12/3/2018

Preserving Impressions photograph Lifting Impressions in Dust/Dirt electrostatic lifting device Casting Impressions dental stone (gypsum) Snow Impression Wax Created by C. Ippolito April 2008 12/3/2018