The Nrc Bullet-Lead Report: Should Science Committees Make Legal Findings?

Abstract

For decades, analysis of concentrations of elements in bullet lead have been used in the United States to link defendants to crimes in which fragments of bullets have been recovered. In response to mounting criticism of the practice, the FBI commissioned the National Academy of Science to review the Bureau's procedures for making these measurements and drawing inferences from them. The Academy's report confirms the validity of the instrumentation but identifies weaknesses in the statistical methods for declaring matches and for describing the significance of these matches. It also concludes that courts correctly could apply existing legal doctrine to uphold testimony that a match makes it more probable (by an unspecified amount) that the defendant is the source of the fragments. The article questions the committee's legal reasoning with regard to the probative value of the evidence and its conclusion as to the admissibility of the evidence under the scientific-validity standard articulated in Daubert v. Merrell Dow Pharmaceuticals, Inc. It also raises a question as to whether and how blue-ribbon scientific committees studying forms of scientific evidence should offer explicit legal opinions on admissibility.

Keywords: evidence, bullet lead, probability, likelihood, probative value, scientific evidence, forensic science, science policy

JEL Classification: C13