Compositional bullet lead analysis (CBLA) was a method used solely in the US by the FBI Laboratory to compare the content of bullet lead and make an attribution of source (manufacturer, production unit, box of bullets). Although the chemical analysis methods used are sound, flaws in the interpretation and statistics lead to misevaluations of evidence and overstating its probative weight. Significant criticism led the FBI to ask the National Academies of Science to convene a Committee to review its methods and protocols. Based in part on the Committee's report, the FBI discontinued CBLA in 2005. Over 2500 cases across several decades were worked by the FBI, and CBLA played a significant role in many of them, including death penalty cases. After reviewing the case of James Otto Earhart, this chapter reviews the FBI's analytical and statistical methods (with minimal math), why their base assumptions were wrong, and examples of testimony that overstated the evidence. CBLA is instructive not only for attorneys who may face appeals cases, but also for fundamental issues that may involve other forensic methods.
