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
: The raised parts of the rifling (lands) and the cut-out parts (grooves) leave parallel scratches on the bullet. bullet fingerprinting
As a bullet travels through a gun barrel, it is gripped by —spiral grooves machined into the metal to make the projectile spin for stability. Bullet fingerprinting, more formally known as , is
The shell casing is also marked by various parts of the firearm's internal mechanism: How It Works: The Mechanical Fingerprint : The
: 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)
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"