LEAD ANALYSIS

Elemental

Elemental lead analysis of ammunition, often referred to as Compositional Analysis of Bullet Lead (CABL), was a technique used in forensic science for almost 20 years before it was abandoned for being non-specific. The FBI used the CABL technique to compare projectiles from a crime scene to projectiles from a specific box of ammunition. The FBI would then use the analytical data as evidence to convict an alleged perpetrator of a crime. The FBI’s methodology, however, was inherently flawed because it relied on specific trace elemental composition of lead, which eventually proved to be similar across all ammunition in numerous boxes made from that specific batch of lead. A study conducted in 2004 by the National Research Council of the National Academy of Sciences concluded that “CABL does not, however have the unique specificity of techniques such as DNA typing to be used as standalone evidence,” leading to their recommendation that CABL not be used as conclusive evidence for a conviction. Accordingly, elemental lead analysis was proven to be “faulty science” in tracing lead in ammunition back to a specific source.

Isotopic

Isotopic compositional analysis is alleged to be yet another forensic science technique for tracing lead in ammunition back to a specific source. Lead contains four stable isotopes found in the environment, including 204, 206, 207 and 208. The isotopic ratios of these four lead isotopes is claimed to conclusively prove “fingerprinting” of the source of lead poisoning in an organism. Although this technique is alleged by a few naïve scientists to be capable of matching blood-lead isotopic ratios found in an organism to specific sources of lead found in ammunition, the realities of lead metallurgy and lead product manufacture show conclusively that such matches cannot legitimately be made.