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 Department of Justice 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. The Innocence Project, one of the groups that worked with the Department of Justice on the issue, explained why the cases are being reconsidered.
Before DNA testing was used in criminal trials, prosecutors throughout the country routinely relied on microscopic hair comparison analysis, often provided by the FBI, to link a criminal defendant to a crime. The practice was deemed “highly unreliable” in the 2009 National Academy of Science report on forensic science, Strengthening Forensic Science in the United States: A Path Forward. As part of the agreement announced today, the agencies acknowledge that there are significant limitations on the probative value of hair analysis because “the size of the pool of people who could be included as a possible source of a specific hair is unknown.”
In 1992, Willie Jerome Manning was convicted of killing two students in Mississippi, in part based on an FBI expert's testimony that hair fragments found in the victims' car were from an African-American male. Manning's capital sentence was stayed after the Justice Department acknowledged the flaws in that testimony.