I'm slightly troubled..

I thought the film was brilliant. Well acted, scripted, and shot, and I would certainly watch it again. The only problem is the ending..I don't get why Saul was given a death sentence. He certainly deserved prison, his actions were devastating and he needed to serve time for it..but death? Really? When there are far worse criminals out there who actually go out and kill people on purpose and get nothing more than life in jail. Is there a reason he was sentenced to death? Was it thought provoking (if it is, it certainly work) or a different state law (as a brit I don't get how USA laws work) or time period? Does anyone know?