Flawed Evidence: The Limits of Science in the Crime Lab

Before DNA testing, prosecutors relied on less sophisticated forensic techniques, including microscopic hair analysis, to put criminals behind bars. But how reliable was hair analysis?

In the late 1980s, DNA technology upended the world of forensics. Genetic fingerprinting, as it was often called, was a powerful tool to win convictions, but it also revealed cracks in the criminal justice system: innocent people were in prison. And many of them had been convicted in part using older forensic techniques, including microscopic hair analysis.

Before DNA, when a hair was found at a crime scene, it was examined under a microscope and compared with hairs from a suspect. Though crime lab analysts knew that two hairs couldn’t be matched with perfect accuracy, hair comparisons proved to be powerful evidence linking suspects to crimes. In court, some examiners and prosecutors were certain that they had a “match.” But DNA exonerations are now forcing the criminal justice system to confront the limitations of hair analysis.

Related:An Overturned Conviction Magnifies Flaws in a Discredited Forensic Technique by Anny Oberlink

  • Producer: Scott Michels
  • Producer: Kit R. Roane
  • Editor: Hope Litoff
  • Editor: Anne Alvergue