An expert witness testifies at a trial to provide evidence in his or her field. Over the course of several decades beginning in the late 1970s, witnesses with the FBI went further, suggesting that particular evidence—hair-match analysis—was a stronger indicator of guilt than the science supports. They tried, in other words, to help prosecute the case.
Now, in an apparently unprecedented move, the Justice Department has agreed to review 120 convictions that may have been influenced by the agents' exaggerated testimony. In 27 of those cases, the convicted individuals were sentenced to death.
Under terms finalized with [advocacy] groups last month, the Justice Department will notify prosecutors and convicted defendants or defense attorneys if an internal review panel or the two external groups find that FBI examiners “exceeded the limits of science” when they claimed to link crime scene hair to defendants in reports or testimony.
If so, the department will assist the class of prisoners in unprecedented ways, including waiving statutes of limitations and other federal rules that since 1996 have restricted post-conviction appeals. The FBI also will test DNA evidence if sought by a judge or prosecutor.
As many as 21,000 cases may have been affected by similar testimony.