Castration. Forget charging him and locking him up, these guys aren't curable. He'll be back out and at it again in a certain number of years. Castrate the bast*rd and let him go harmlessly into society. That's punishment enough, and no more victims in his wake.
I've read even castration doesn't really work. Their minds are the repository of their sick desires and they often will still act them out one way or another.
Execution is the only cure.