If you're referring to the murderer that Selina set free, the answer is that the murderer didn't actually kill anyone. She--the non-murderer and Selina's friend--went for a ride with this guy. He wrecked the car they were in and promptly died. However, when the cops arrived, they found a dead body in the trunk. Sel's friend had nothing to do with the murder, but everyone thought she did so she ended up getting convicted and sentenced to the death penalty. Luckily, she has a good friend.