Murder is not the only offense that is "serious" enough to be punishable by death. For example, criminals who have raped several people, or child molesters, kidnappers, etc. Just because the victim didn't die during the offense, doesn't mean they don't have emotional and physical scars, which in result makes them wish that they were (dead). Lots of crimes other than murder deeply affect the victim and their lives in the future, and therefore should be punished more seriously then they are today.
I believe that murder is the only crime that is "serious" enough to have the death penalty, Yes rape and others crimes like that could be considered a serious crime but do we really need to put rapist on death row? The answer is no, why can't we just put the in prison for life without parole. Life in prison without parole is much worse then death penalty because your in prison all alone that would suck. I believe that if you didn't kill someone you don't deserve to die but you do deserve a punishment depending on what you did.