Prosecutors have failed to notify hundreds of defendants and their attorneys about faulty FBI forensics work that may exonerate them, according to an in-depth Washington Post investigation. The Justice Department spent nine years—from 1996 to 2004—conducting what it calls an "exhaustive" review of 13 agents' forensic work from the 1990s, and found more than 250 questionable cases. But it only revealed that information to prosecutors, and in more than half of those cases, prosecutors kept that information to themselves, the Post discovered. It also found that the DOJ only reviewed the hair and fiber work of one FBI agent, though it was told other examiners' work in that discipline should be questioned.
In one case, prosecutors left a convicted murderer in prison for 12 years after discovering that work leading to his conviction was flawed, before DNA testing finally exonerated him. In another, a man was executed before the DOJ got around to examining his case. The problem with hair analysis, the Post explains, is that there's no consensus on how many common characteristics are needed to "match" two samples. In one case, the Post found that an analyst only matched three—that the hair was black, human, and from an African American—but implied to the jury that he'd used "around 15," and that mistaken matches were "very rare." DNA evidence shows the defendant was almost definitely innocent.