[I strongly agree to bring back death penalty too on those who committed grievous crimes . Well I think the authorities would really prove that a killer really killed someone so as not to give wrong verdict.
The problem will be, that said "authorities" will have a very different view on what is a "grievous crime" than you have. Just check in any country of your choice which offenses are punished harder than murder, and you'll find the whole range of political offenses. And those are not what they tell you.