Befriend him. He probably doesn't have a lot of friends.
Talk, here his side of the story, and ask whether or not you can forgive him of that crime, whatever it may be. Everyone has their own story, and we owe it to ourselves as enlightened humans
Forgiveness is a beautiful thing who knows, until you give us the whole story, we can't say much more than that
I don't know the crimes he was convicted of (obviously( but I'd at least like to hear why he did it. Understanding someone's viewpoint is never a bad thing. Just be careful about it.