In the 25 years since Thomas E. Haynesworth went behind bars as a 130-pound teenager, he has befriended two inmates who, like himself, were convicted rapists. Earlier this decade, DNA testing of evidence discovered in old state forensic laboratory files proved those friends, Marvin Anderson and Julius Ruffin, innocent and implicated the real assailants.

No one ever claimed the criminal-justice system was perfect. But until 20 years ago, it was difficult to prove otherwise. Since then, 225 innocent people—10 in Virginia—have been exonerated of crimes by DNA testing. However, DNA is not a factor in most cases, and the rate of wrongful convictions remains unclear. That could change, in part, because of a large, groundbreaking and sometimes hotly contested review of old cases under way in Virginia.