I'm for a form of the Death Penalty.
There are plenty of cases where there is no doubt as to the guilt of the murderer. They were caught in the act, they confessed, etc. In those cases, I'm all for the death penalty.
There are also plenty of cases where people are convicted on circumstantial evidence and there is no "smoking gun". In those cases, a life sentance would be better. You never know that maybe new evidence is found or a new way of determining who was at a crime scene. I know of a case where a guy was convicted of rape and murder. All the available evidence pointed to him. He was also known as a habitual criminal. It all fit. But 20 years later and DNA testing became available. Once he got the DNA testing done, it proved he wasn't the rapist or killer. He lost 20 years of his life for a crime he did not commit, but he was alive and free to go(with a good amount of money from the state) for all his troubles.