The FBI has admitted that 26 out of 28 examiners in the agency's elite microscopic hair comparison unit overstated forensic matches during criminal trials for more than two decades, reports The Washington Post. Prior to 2000, examiners gave flawed testimony that may have helped prosecutors in more than 95 percent of 268 trials, according to the National Association of Criminal Defense Lawyers and the Innocence Project, both of which have been helping the government conduct the largest review of post-conviction forensic evidence in the US to date.

Flawed testimony in 95 percent of cases

"The FBI’s three-decade use of microscopic hair analysis to incriminate defendants was a complete disaster," Peter Neufeld, co-founder of the Innocence Project, told The Washington Post. "We need an exhaustive investigation that looks at how the FBI, state governments that relied on examiners trained by the FBI, and the courts allowed this to happen and why it wasn’t stopped much sooner."

FBI examiners systematically told the court that the visual hair matches made in their labs were near-certain, according to The Washington Post. Moreover, they used misleading statistics to support their testimonies, despite the fact that there is no research that shows how often hair from different people can look the same. Today, forensic scientists tend to use visual hair comparison to rule out possible suspects instead of using it as evidence for guilt. And when they do use it as evidence for guilt, they combine it with genetic testing.

The FBI's admission doesn't mean that there was no other evidence supporting the convictions, but it does raise questions about whether some people have been wrongfully incarcerated. After all, this has happened before. In 2002, the FBI reported that more than 11 percent of hair matches made by its examiners were false. As a result, five defendants have been exonerated since 2009; they had all served 20 to 30 years in prison for murder or rape.

No written standards explaining how examiners should define results

The announcement highlights a massive failure of forensic science — a science that, in some cases, has had to battle claims that it's no more than "junk science." But a lot of questions remain. We still don't know why these errors occurred because the FBI wants to complete all the reviews before assessing the causes. Still, the agency has admitted that examiners in this unit didn't have written standards explaining exactly how they should define forensic match results in court until 2012. And the microscopic hair comparison unit is actually ahead of the curve. Nineteen other forensic disciplines lack these standards, according to the FBI. The agency plans to change that this year.