Every ﬁrearm leaves unique, reproducible markings on expended bullet and cartridge cases that it ﬁred. The barrel, ﬁring pin, ﬁring chamber, extractor, ejector and other parts of the gun leave these marks, called tool marks, on the bullet and cartridge case faces. Individually and collectively, these markings function as the “ballistic signature” of the ﬁrearm.
Automated Firearms Identiﬁcation System (AFIS) are specialized computer hardware/soware combinations designed to capture, store and rapidly compare digital images of bullets and cartridge casings.
Law enforcement agencies worldwide utilize AFIS to rapidly generate Candidate Lists of probable matches of a suspect bullet/cartridge against the ballistic database. Depending on the agency’s requirements, AFIS will generate the Top 10, Top 20, etc. list of probable matches. The Firearms Examiners then use these candidate lists to select the actual bullets/cartridges they will visually compare with the suspect bullet/cartridge.