Since the 1960s, the FBI has used “bullet matching” as evidence in criminal cases. However, recently the practice has been successfully challenged in a number of cases. Public defenders and watchdog organizations are now bringing challenges to help identify defendants who were wrongfully convicted using such evidence.
Bullet matching was first used to investigate the assassination of President John F. Kennedy, and was central to FBI criminal testimony for 40 years. The procedure rests on the assumption that all bullets molded in the same batch should have the same chemical makeup, and thus an investigator would be able to identify whether a fragmented bullet matched those in a suspect’s possession. Bullet-matching has been used in thousands of trials, and has been a pivotal factor in proving guilt in several dozen.
The FBI eliminated bullet-matching from its criminal investigations after former agent William Tobin brought to light its statistical inconsistencies and the large margin of error inherent in its use. After thorough investigations by both Tobin and the National Academy of Sciences, it became apparent that bullets within the same box could have varying chemical make-ups, and more importantly, up to 35 million bullets with the same composition could exist at any one time.
Today, Barry Scheck from the Innocence Project has dedicated himself to publicizing the error rates of bullet matching so that wrongly convicted defendants may appeal their sentences. Several have successfully appealed their convictions, but for some, the time to appeal their sentences may already have passed.