In the summer of 1984, a young girl was kidnapped, raped, and murdered near her home in Baltimore County, Maryland. Twenty-three-year-old Kirk Bloodsworth was accused of the crime, and he was convicted and sentenced to death after a jury trial based largely on the eyewitness testimony of some boys playing near the murder site.

Three days after Bloodsworth's conviction, police and prosecutors learned about David Rehill. Hours after the girl's murder, Rehill had shown up at a mental health clinic with fresh scratches on his face and had mentioned to therapists that he was "in trouble with a little girl." Rehill closely resembled Bloodsworth, who was already on death row. Six months passed before police decided to interview Rehill. Nevertheless, they did not place him in a lineup or doublecheck his alibi.

Due to a technical error in the trial, Bloodsworth was granted an appeal two years after his...