Gunshot Residue Analysis STEM

Gunshot Residue (GSR) Two types: GSR deposited on victim, clothing or target that follows the path of the bullet GSR deposited on the shooter’s hands primarily from the primer

Gunshot Residue (GSR) Gunpowder Chemistry Major detectable elements are: lead (Pb), barium (Ba) & antimony (Sb) Virtually all cartridge cases are made of brass (copper & zinc); also detectable.

GSR: A Revolver Being Fired

GSR: The Firing of an AK-47

Chemical Testing of GSR Modified Griess Test Specific for partially burned and unburned gunpowder particles, most specifically, nitrates found in the partially burned gunpowder Sodium Rhodizonate Test Specific for lead Vaporous lead is usually found closer than arm’s length

Results of GSR Hand Test Negative results may be caused by: Washing the hands Shooter may have been wearing gloves Lead free ammunition A rifle or shotgun may not deposit GSR on hands

GSR on the hand of a suicide victim, proving he was holding the weapon when it was fired.

GSR Testing of Hands Swabs are taken of the suspected shooter(s) hands Examined under the Scanning Electron Microscope (SEM) Tests for Lead, Antimony, and Barium particles Studies suggest it stays on the hands approximately for 6 hours

SEM of GSR Particle

Any Questions?

Video: Gunpowder signature may help solve crimes (2.5 min)

References Richard Ernest Forensic Ballistic Consultant website: http://outzonebbs.net/gunlab/home.shtml Introduction to Forensic Firearms Identification website: http://www.firearmsid.com/new_index.htm http://www-medlib.med.utah.edu http://www.fbi.gov/hq/lab/fsc/backissu/april2000/schehl1.htm http://www.youngguns.btinternet.co.uk/shotguns.htm http://members.tripod.com/k_nibin/ http://www.intercom.net/npo/fop/pdpatches/ATF_jpg http://www.aeroballisticsonline.com/ballistics/bulletsc.html http://www.production-machining.com/articles/0703tb1.html This presentation is available because of the expertise of John Romeo, Firearms Analyst with the Florida Dept. of Law Enforcement