Firearms examination is a discipline of forensic science which has as its primary concern to determine if a cartridge case, bullet or other ammunition component was fired in a specific firearm. This is actually a form of toolmark examination where the firearm, because it is made of material harder than the ammunition components, acts as a tool to leave impressed or striated marks on the various ammunition components that come into contact with the firearm.
Firearms that are submitted are tested to determine if they function properly, and then they are test fired under laboratory conditions. This provides the examiner with exemplars from the firearm that may be compared to other evidence items.
Firearms may also be submitted in which an attempt has been made to obliterate the serial number. Even if the metal surface is ground away or filed down, the structure of the metal molecules that remain may retain the structure of the original stamp. Serial number restoration may be performed by polishing, or by a variety of chemical or magnetic means, and may result in the restoration of a partial or a full serial number.
The Jefferson County Regional Crime Laboratory Firearms section has one Forensic Firearms Examiner. In February of 2014, the Laboratory was accredited to perform full firearms analysis, including microscopic comparison and identification. This is the first time these services have ever been offered by a local entity. In addition to those new services, the Firearms section routinely performs functionality evaluations, serial number restorations, and also generates test fires for comparison. Suitable items are imaged into the Integrated Ballistics Identification System (IBIS)/Brass TRAX database in hopes of generating investigative leads on entered specimens.
Gunshot residue and distance determination is the examination of clothing and other items for the presence of gunshot residue or shot patterns in an attempt to determine muzzle-to-object distance. Although these examinations are not conducted at the Jefferson County Regional Crime Laboratory, it is important that submitting agencies be aware of the potential forensic information that may be gained through these examinations. The Laboratory’s Firearms Examiner is familiar with the requirements for these examinations and works closely with Examiners who perform them. The Crime Lab is happy to assist with the pursuit of any additional examinations which may be of forensic benefit to a criminal case.