: The pin strikes the primer at the back of the casing, leaving a unique indentation.
: The hooks and pins that pull the spent casing out and toss it away leave distinct scratches on the rim. The Technology of Tracking bullet fingerprinting
: These systems can often provide investigative leads within 24 to 48 hours by flagging potential matches across different crime scenes. Limitations and Controversies : The pin strikes the primer at the
: When the gun fires, the casing is forced backward against the breech face, transferring its texture to the metal. Limitations and Controversies : When the gun fires,
: 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)
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