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Saturday, March 30, 2013

What is Forensic Firearms Identification?

     In the past called forensic ballistics, forensic firearms identification concerns itself with the comparison of crime scene bullets and firing pin impressions on shell casings with the marks on test-fired rounds in the crime lab. If the marks left on the bullet as the projectile passed through the test-gun barrel are identical to the rifling (grooves inside the barrel) scratches on the crime scene slug, the crime site weapon has been identified. If the firing pin impressions on the known and crime scene shell casings match, an identification has been made as well. (Semi-automatic weapons also leave ejector marks on shell casing that can be compared and identified.)

     Forensic firearms identification is a science grounded on the principle that no two guns will leave the same marks on the ammunition. Bullet scratches (called striations) and firing pin impressions are as unique as a person's fingerprints.

     Firearms identification also includes restoring filed-off serial numbers, tracing projectile flights, identifying the various types of bullet wounds, and determining the range of close shots through muzzle produced powder-stain patterns.

     Experts in the field apply the sciences of metallurgy, chemistry (gunshot residue analysis), microscopy, and ballistics. A knowledge of the gun smith trade is also useful. Like forensic document examiners, forensic firearms experts are trained on-the-job in crime laboratories.  

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