The FBI formally acknowledged this month that, for decades, nearly every examiner in its microscopic hair comparison unit gave flawed testimony declaring that crime scene hair evidence "matched" the hair of defendants.
A review of 268 trials in which hair evidence was used against defendants revealed that 26 of the FBI Laboratory's 28 examiners overstated forensic matches, and that flawed testimony favored the prosecution more than 95 percent of the time. These FBI examiners trained 500 to 1000 state and local crime lab analysts in the same flawed techniques.
The FBI admitted it provided inaccurate expert testimony in 32 capital trials that ended in a death sentence. Nine of those defendants have been executed.
Forensic evidence relying on subjective comparisons of hair, bite marks, and toolmarks have contributed to wrongful convictions in more than a quarter of the 329 cases since 1989 where DNA evidence exonerated the defendant. Improper hair comparison testimony has contributed to at least one wrongful execution .
Sen. Richard Blumenthal, a former prosecutor, said the findings are "appalling and chilling in their indictment of our criminal justice system." He called on the FBI and Justice Department to notify defendants in all 2500 cases where the FBI Lab reported a hair match, and to work harder to retrieve information on every case. To date, review has been prevented in 700 cases because police or prosecutors have not responded to requests for information.
The federal investigation into hair comparison evidence started after the Washington Post reported in 2012 that flawed hair matches might have led to hundreds of wrongful convictions for murder, rape, and other violent crimes nationwide since the 1970s. The review has confirmed that FBI experts systematically testified to the near-certainty of hair “matches," citing incomplete or misleading statistics drawn from their case work. There is no accepted research on how often hair from different people may appear the same.