Hundreds of innocent men and women may be languishing in prisons across the US because of bad forensic methods at the FBI.

At the centre of the problem is microscopic hair analysis. Between 1973 and 1999, the forensic testimony of an FBI agent about hairs found at a crime scene was a crucial piece of evidence leading to a person's conviction.

However in 2012, after three high-profile exonerations in hair-related cases, the FBI began an internal review of how its agents had undertaken hair analysis.

In a damning assessment it found that the testimony of its staff was scientifically invalid 95 percent of the time.

With hundreds of potentially innocent people living behind bars - how will the criminal justice system and the FBI respond?

Fault Lines investigates the legacy of bad forensic science and the many lives it continues to affect today.

Source: Al Jazeera