The death penalty is not a deterrent for violent crime. It has also been used in cases where innocence was proven later. We can let someone out of prison, but we can never give them back life. If it is not a deterrent and there is potential for a grave nonretractable mistake, then I see no reason to continue its use in America.
It should also be noted that in spite of the extended use of the death penalty in the United States, our country does not have lower criminality rates than other countries where it is not in use. According to a study conducted by the Taiwan government, the United States annually witnesses as many as 6.32 murders per 100,000 inhabitants, whereas countries such as Spain (1.08) or Japan (0.58), which do not use the death penalty, have dramatically fewer murders. (Japan does have a death penalty, but it is systematically commuted to a life sentence.) In fact, only the Russian Federation (18.07) has higher murder rates. This tends to prove that death penalty does not dissuade people from commiting crimes. Other approaches should be considered to solve our criminality issues.
The financial cost of executing a prisoner in the United States has been shown repeatedly to be far higher than life imprisonment. All issues of deterrence and morality aside, the financial cost is not worth it.
Facts on Deterrence and the Death PenaltyRyan Matthews is 115th Death Row Inmate Freed
Innocence Project