To manage these vast amounts of data, law enforcement uses specialized databases and imaging systems.

: When the gun fires, the casing is forced backward against the breech face, transferring its texture to the metal.

: Microscopic flaws in the manufacturing process or wear and tear from use create a "signature" unique to that specific barrel. 2. Impression Marks (on the casing)

: The hooks and pins that pull the spent casing out and toss it away leave distinct scratches on the rim. The Technology of Tracking

Despite its usefulness, "bullet fingerprinting" is not always a definitive proof of guilt. Several factors can complicate or even invalidate a match. 1. Barrel Evolution

The shell casing is also marked by various parts of the firearm's internal mechanism: