firearms / toolmarks identification

The basic principle of firearms examination is based on the fact that most machined parts will have unique marks, which can be transfered to other surfaces. Almost all gun barrels, as well as the machined areas in the weapon's firing mechanism, leave unique marks on bullets fired through the barrel and on cartridge cases worked through the firearm. A firearms examiner deals with the analysis of both firearms and ammunition of all types. The Firearms Examiner also determines whether a bullet originated from a suspect firearm. Impacted items which were on the receiving end of a discharged bullet are also examined for discharge residues in an attempt to ascertain muzzle distance.

As each machined gun barrel is unique, so too are all machined tools. These tools leave distinct marks on most objects they contact. A toolmark is any machined impression transfer caused by the tool coming into contact with an object. A toolmark examiner compares toolmarks in order to determine what type of tool, or what exact tool, was used to make a specific mark.