Bullet fingerprinting, also known as ballistic fingerprinting or ballistic identification, is a technique that can help identify the gun that fired a bullet from an analysis of the unique marks that every gun makes on the bullet it fires and on the shell ejected from it . This can be useful for solving crimes involving firearms, as it can provide evidence of who used the weapon and when.

Bullet fingerprinting works by comparing the microscopic grooves, scratches, and impressions that are left on the bullet and the shell casing by the gun’s barrel, breech face, firing pin, extractor, and ejector. These marks are like fingerprints that can be matched to a specific gun using a database of ballistic images or a manual examination by a forensic expert. The accuracy of bullet fingerprinting depends on several factors, such as the quality of the bullet and the shell casing, the condition of the gun, and the availability of reference samples.

One of the challenges of bullet fingerprinting is that guns can change their marks over time due to wear and tear, modifications, or intentional alterations. Therefore, it is important to update the ballistic databases regularly and to collect multiple samples from different guns of the same make and model. Another challenge is that some types of bullets, such as hollow-point or frangible bullets, can deform or fragment upon impact, making it harder to recover and analyze them.

Bullet fingerprinting is not a new concept, as it has been used since the early 20th century in various cases around the world. However, it has gained more attention in recent years due to advances in technology and research that have improved its reliability and efficiency. For example, experts have developed a unique method for retrieving high-resolution images of bullets in 3D using X-ray computed tomography. This can help overcome some of the limitations of traditional 2D imaging methods and provide more accurate and detailed information.

Bullet fingerprinting is not a foolproof method, as it can be affected by human error, bias, or tampering. However, it can be a valuable tool for forensic investigations when used with caution and in conjunction with other types of evidence. By applying bullet fingerprinting, law enforcement agencies can potentially solve more crimes involving firearms and bring justice to the victims.

Some examples of cases where bullet fingerprinting played a key role in the investigation are:

• The St. Valentine’s Day Massacre in 1929, where forensic expert Calvin Goddard linked bullets and cartridge cases from a crime scene to two Thompson submachine guns used by Al Capone’s gang to kill seven rival gang members in Chicago.
• The assassination of John F. Kennedy in 1963, where NIST scientists used advanced imaging techniques to create digital replicas of the bullets and fragments that were recovered from the president’s body, the limousine, and the governor of Texas. These replicas helped preserve the historical artifacts and provide more information about their origin and trajectory.
• The Beltway sniper attacks in 2002, where ballistic fingerprinting helped link 13 shootings in the Washington D.C. area to a single Bushmaster rifle that was found in the possession of John Allen Muhammad and Lee Boyd Malvo. The FBI used a database of ballistic images called the National Integrated Ballistic Information Network (NIBIN) to match the evidence.

Bullet fingerprinting is not only useful for solving crimes, but also for preventing them. By requiring gun manufacturers and dealers to record and submit ballistic fingerprints of new and used firearms to a national database, law enforcement agencies can potentially trace guns used in crimes back to their original owners and track illegal gun trafficking. However, this proposal has faced opposition from gun rights advocates who argue that it would infringe on their privacy and constitutional rights.