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
Unlike human fingerprints, a gun's "fingerprint" changes over time. Every shot fired slightly alters the microscopic striations in the barrel. Experts may only fire a limited number of test rounds because the fifth shot might already look different from the first. 2. Success Rates and "Expensive Failures" bullet fingerprinting
Bullet fingerprinting, more formally known as , is a forensic technique used to match a fired bullet or shell casing to a specific firearm. The "fingerprint" consists of unique, microscopic marks left on the ammunition by the gun's internal components during the firing process. While often portrayed as a flawless investigative tool in television dramas, the reality of its scientific reliability is a subject of significant debate within the forensic community. How It Works: The Mechanical Fingerprint more formally known as
The shell casing is also marked by various parts of the firearm's internal mechanism: Barrel Evolution Unlike human fingerprints
Barrel uniqueness in firearms: reliable forensic match? - Facebook