Capital punishment – is it required?

That is a very hot topic in my country right now. In my opinion, the only benefit from capital punishment would be to put a decline on the growing population. I don't believe it serves any good purpose and it is just an extra way to sin. Why should one be judged by man. I understand imprisonment but when you take it to the point of killing the person, what exactly are you proving. I don't think it will act as a detergent for criminals thinking of doing their bad deeds as I'm pretty sure most crime is only premeditated to the point of action. I always think it would be better if the government took the criminals they have locked up and sent them to fight the wars going on in the world since they like to kill or whatever they like doing.