Josiah Sutton was convicted of rape. He was five inches shorter and 65 pounds lighter than the suspect described by the victim, but at trial a lab analyst testified that his DNA was found at the crime scene. His case looked like many others--arrest, swab, match, conviction. But there was just one problem--Sutton was innocent.

We think of DNA forensics as an infallible science that catches the bad guys and exonerates the innocent. But when the science goes rogue, it can lead to a gross miscarriage of justice. Erin Murphy exposes the dark side of forensic DNA testing: crime labs that...