This should be a contreversal comment, so I'm going to say now that I'm just posting this rebuttal and not getting into an e-argument.
The criminal system isn't for punishment. It's for reform. It's not to 'get back' at people, it's to help integrate people back into society and act as a deterrent to stop crime in the first place. You're not trying to 'execute this fucker and others like him', you're trying to figure out what's wrong, how you can reform (if possible), and deter other crimes like it. If you're just executing it's a hell of a deterrence, but you're not reforming at all.
Remember the Oslo masscare? Read up on the perpetrator and his sentence. http://en.wikipedia.org/wiki/Anders_Behring_Breivik