John McCormick, a 63-year-old cab driver, was on his porch the morning of July 26, 1978, when he was robbed and shot dead. His wife, awakened by the commotion, reported that she saw the assailant flee wearing a face stocking, which investigators later found near the scene. Police identified 17-year-old Santae Tribble as the prime suspect after an informant linked him to the gun. At Tribble’s trial, an FBI agent testified that one of the hairs found in the stocking “matched in all microscopic characteristics” to Tribble. While half a dozen witnesses corroborated Tribble’s alibi, the hair was enough to convince the jury. Tribble served 23 years before he was paroled in 2003. Nine years later, mitochondrial DNA testing on the same hair samples revealed that Tribble was no match at all. In fact, one of the hairs was canine.