God had a little help from a group of college kids. Last fall several Northwestern University students taking an investigative-journalism class with Prof. David Protess delved into Porter’s case. They scoured records and re-enacted the crime in a Chicago park, concluding that the original police reports didn’t add up. They then located witnesses who’d helped convict Porter but who now say police pressured them to lie. Confronted with the new evidence, Simon gave his videotaped statement to a private detective working with the students. Remarkable as it is, the coup has a precedent: in 1996 three students taking the same class with Protess helped clear four Illinois men convicted of another double murder.

Porter’s case will spur even more second-guessing of capital punishment in Illinois, where he could be the 10th man freed from death row. (Porter was released after an emotional court hearing but hasn’t yet been formally exonerated.) Chicago newspapers are already clamoring for a moratorium on executions. The problem, says Richard Dieter of the anti-execution Death Penalty Information Center, isn’t that Illinois courts make more bad decisions than those in other states. It’s that there aren’t enough dogged lawyers–or college students like Protess’s–to double-check the cases of all 3,500 American prisoners now waiting to die.