Apr 20th, 1:00 PM - 4:00 PM
Bullet Lead Analysis: Unreliable and Potentially Misleading
Comparative Bullet Lead Analysis (CBLA) is a forensic technique that utilizes analytical chemistry to identify amounts of trace elements such as copper, arsenic, antimony, and tin within bullets. These tests are performed to link crime scene bullets to other bullets possessed by suspects. The analysis is based on the theory that every batch of lead has a unique elemental makeup. These assays are typically employed when the firearm involved in a crime has not been recovered or when the physical markings of a fired bullet are too mutilated for comparison. This technique was introduced after President John F. Kennedy’s assassination in 1963 and has since been used in approximately 2500 cases by the FBI. However, in 2002, the FBI asked the National Research Council (NRC) to evaluate the scientific basis of comparative bullet lead analysis1. The NRC concluded that variations in the manufacturing process of ammunition rendered the science “…variations among and within lead bullet manufacturers make any modeling of the general manufacturing process unreliable and potentially misleading in CABL comparisons.”2 This study examines: the scientific history of CBLA as well its history in the courts. These findings are being used to examine several Idaho criminal cases where CBLA played a key role.
1. FBI Laboratory Announces Discontinuation of Bullet Lead Examinations; Sept. 1 2005. www.fbi.gov/pressrel/pressrel05/ bullet_lead_analysis.htm
2. Forensic Analysis: Weighing Bullet Lead Analysis, the Committee on Scientific Assessment of Bullet Lead Elemental Composition Comparison, National Research Council, p112, 2004 See also http://books.nap.edu/catalog.php?record_id=10924