Fifteen years ago, DNA analysis was nonexistent. Today, more than seventy inmates accused of rape and murder have been freed because DNA tests proved their innocence in a way that evidence, courtroom testimony, and eyewitness accounts never could. Why then are prosecutors, courts, and even governors reluctant to use this scientific test? And when evidence has been tested and DNA does not match that of the accused, how can the law overlook the results? FRONTLINE investigates the reasons why inmates remain in prison despite DNA evidence that excludes them as the perpetrators.