Hundreds of defendants sitting in prisons nationwide have been convicted with the help of an FBI forensic tool that was discarded more than two years ago. But the FBI lab has yet to take steps to alert the affected defendants or courts, even as the window for appealing convictions is closing, a joint investigation by The Washington Post and 60 Minutes" has found. The science, known as comparative bullet-lead analysis, was first used after President John F. Kennedy's assassination in 1963. The technique used chemistry to link crime-scene bullets to ones possessed by suspects on the theory that each batch of lead had a unique elemental makeup. In 2004, however, the nation's most prestigious scientific body concluded that variations in the manufacturing process rendered the FBI's testimony about the science "unreliable and potentially misleading." Specifically, the National Academy of Sciences said that decades of FBI statements to jurors linking a particular bullet to those found in a suspect's gun or cartridge box were so overstated that such testimony should be considered "misleading under federal rules of evidence." A year later, the bureau abandoned the analysis. But the FBI lab has never gone back to determine how many times its scientists misled jurors. Internal memos show that the bureau's managers were aware by 2004 that testimony had been overstated in a large number of trials. In a smaller number of cases, the experts had made false matches based on a faulty statistical analysis of the elements contained in different lead samples, documents show. The government has fought releasing the list of the estimated 2,500 cases over three decades in which it performed the analysis. For the majority of affected prisoners, the typical two-to-four-year window to appeal their convictions based on new scientific evidence is closing.

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