What Caspian wrote in another thread :
'....If they manage to live long enough to be an effective swordsman, etc.. (you know, because they probably spent a lot of their life in jail) and manages to catch a few people out and forces them to Spirit Walk, then yeah, a few people have to take a walk, which may shorten their overall life some, but you can bet the nearest town will form a militia or something and track them down. Get a little evidence off of them for the crimes they've committed and they'll have shaved off another couple decades from their life.'
2 important things :
-they won't go to jail unless someone catches them, something that an experienced griefer will easily avoid... outrunning, disguise, logging off, bribing NPCs, even fighting the pursuers. So it won't be easy to bring them to justice. But... if there's a very high reward on their head, bounty hunting might prove to be a very profitable business.
-they won't go to jail unless there's real evidence against them... again, something they might exploit... or not, depending on the evidence system. In any case, some witnesses won't submit the evidence each time they see a crime. Or... it might be a crime in a remote location, or without any evidence...