Since the 1960s, testimony by representatives of the Federal Bureau of Investigationin thousands of criminal cases has relied on evidence from Compositional Analysis ofBullet Lead (CABL), a forensic technique that compares the elemental composition ofbullets found at a crime scene to the elemental composition of bullets found in asuspect''s possession. Different from ballistics techniques that compare striations onthe barrel of a gun to those on a recovered bullet, CABL is used when no gun isrecovered or when bullets are too small or mangled to observe striations. ForensicAnalysis: Weighing Bullet Lead Evidence assesses the scientific validity of CABL, findingthat the FBI should use a different statistical analysis for the technique and that,given variations in bullet manufacturing processes, expert witnesses should makeclear the very limited conclusions that CABL results can support. The report also recommendsthat the FBI take additional measures to ensure the validity of CABLresults, which include improving documentation, publishing details, and improvingon training and oversight.