Firearms examinations.(Evidence Examinations)

Firearms

Firearms examinations can determine the general condition of a firearm and whether the firearm is mechanically functional or in a condition that could contribute to an unintentional discharge. Trigger-pull examinations can determine the amount of pressure necessary to release the hammer or firing pin of a firearm. Examinations can determine whether a firearm was altered to fire in the full-automatic mode. Obliterated and/or altered firearm serial numbers can sometimes be restored. Firearms can be test-fired to obtain known specimens for comparison to evidence ammunition components such as bullets, cartridge cases, and shotshell casings.

Comparisons of suspect firearms can be made with firearms depicted in surveillance images. Photogrammetry can determine the length of the weapon(s) used by the subject(s) depicted in the surveillance films. See Image Analysis Examinations.

Bullets

Fired bullets can be examined to determine the general rifling characteristics such as caliber and physical features of the rifling impressions and the manufacturer of the bullets. The microscopic characteristics on evidence bullets can be compared to test-fired bullets from a suspect firearm to determine whether the evidence bullet was fired from that firearm.

Cartridge Cases or Shotshell Casings

Cartridge cases or shotshell casings examinations can determine the caliber or gauge, the manufacturer, and whether there are marks of value for comparison. The images of questioned cartridge cases and shotshell casings can be scanned into the National Integrated Ballistics Information Network to compare with evidence from other shooting incidents. The microscopic characteristics of evidence cartridge cases and shotshell casings can be examined to determine whether they were fired from a specific firearm.