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Firearm Identification: In the Forensic Science Laboratory

February 14, 2011 Comments off

Firearm Identification: In the Forensic Science Laboratory (PDF)
Source: National District Attorneys Association

This monograph serves to introduce the prosecutor to the principal elements of one of the forensic specialties, the science of “firearm and toolmark identification.” Many of the words and terms printed in bold in the text are defined in the glossary.The monograph provides an introductory discussion of the specialty of toolmark identification when the tool in- volved is a firearm.The tool surfaces represented here involve one or more of the following: the interior of the barrel, the chamber, parts of the action, and ammunition magazine components.These surfaces of the firearm can produce toolmarks on fired and unfired ammunition components.The forensic scientist views a “tool” as the harder of two objects where the surface of the harder “tool” produces toolmarks on a softer material. For example, the tool surface of the hard barrel interior leaves toolmarks on the softer metal of the fired bullet. Another example is when a cartridge is fired in a firearm.The softer metal used in the cartridge case construction may show toolmarks caused by the interior chamber and action surfaces coming in contact with the cartridge case. The action is the firearm’s loading and firing mechanism.

For there to be a potential for toolmark identification, the tool working surface (1) must have individuality, and (2) the toolmarks must be reproducible for comparisons. If it is deter- mined that the individual character of the tool working surface is reproduced in the toolmarks from repetitive markings, an examiner may be able to make an identification in later compaisons.

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