An expert panel says that an FBI forensic technique long used to link bullets with assailants is scientifically flawed and potentially misleading to juries, the Los Angeles Times reports. The conclusion could affect hundreds of past convictions.
The method measures the likelihood of a chemical match between bullets found at crime scenes and those found in a defendan’s possession. It has been used for more than three decades. in criminal cases involving gun violence. The Times obtained a draft of key sections of the report, which is expected to be released by the National Research Council next month.
“In the future, it would be very difficult for prosecutors to get that kind of evidence admitted,” said William C. Thompson, a professor of law and criminology at the University of California at Irvine. “It raises substantial concerns about the viability of convictions obtained based on such statements in past cases.” He called the report “a slap in the face of the FBI.”
The report is “a very substantial development – a significant indictment of the technology,” said David L. Faigman, a professor of law at the University of California Hastings College of the Law in San Francisco. “The NRC has such prestige that I can’t imagine that a court, after the NRC report, would permit this kind of testimony.”
FBI examiners often say that a bullet can be traced to a specific manufacturing batch. The technique offers a way to solve gun crimes when no gun was found. A Times investigation published in February suggested that the FBI’s use of lead-analysis evidence might have been based on faulty assumptions that greatly overstated its scientific significance.