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Gunshot Residue

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Jaimie Barnes

on 24 April 2013

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Transcript of Gunshot Residue

Jaimie Barnes Gun Shot Residue in Forensic Investigation What is Gun Shot Residue? Other Firearm Evidence - Gun Shot Residue (GSR) is the burnt and unburnt gunpowder that is propelled from a firearm as it is fired. From hands or surfaces - using adhesive 'stubs' How is it collected? Did the suspect fire a gun? How is it used? If a person has fired a gun, been near a gun fired, handled a gun or ammunition, contacted a surface with GSR - then GSR could be present. What can it really tell us? Serial numbers and registration Primer GSR is created by the ignition of the primer and contains particles of lead, barium and antimony. Sources http://www.focossforensics.com/html/gunshot_residue.html Powder GSR creates pattern evidence as it is expelled through the muzzle of a firearm. It contains un-burnt and partially burnt gun powder, particulate metals and nitrites. To be analyzed with scanning electron microscope or X-ray analyzer Stubs Versus Swabs? A Comparison of Gunshot Residue Collection Techniques. Visual or physical collection of evidence with clear powder burns Can be used to determine distance from which gun was fired from. Infrared film with filters or Video spectral comparator To visualize residue marred by dark clothing or bloodstains Visualization of Gunshot Residue Patterns on Dark Clothing Determine the distance from the firearm to the victim when fired. Was this person near when the gun was fired? If a person did not fire a gun, fired one but did not get GSR on the sampled area, or washed, wiped or otherwise removed GSR after firing a gun, before the sample - then GSR could be absent. GSR on hands - http://oag.ca.gov/sites/all/files/pdfs/cci/reference/peb_15.pdf GSR on victim - GSR on the victim, usually on clothing, can be compared with known-distance test firings of the firearm, or similar, to determine the distance between the muzzle and victim when it was fired. Tests to use in examination include Modified Griess Test (nitrite residues), Dithiooxamide Test (copper-bearing bullet), Sodium Rhodizionate Test (lead). Careless evidence handling, medical personnel, object obstructions, dried blood or other debris, water, fired from beyond maximum deposit distance. GSR affected by - Contact Shots - When fired at a close range the affects of a gunshot and residue are clear, including ripping, tearing, burning, melting of cloth / fibers and high concentrations of GSR. http://library.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNGSR.html http://www.firearmsid.com/a_distancegsr.htm National Institute of Justice: Firearm Examiner Training Distribution of gunshot residues – The influence of weapon type Latent Fingerprints - Firearm, casings, magazine DNA Ballistics - Bullets, casings, trajectories
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