There is an entire underground society in the prison system which makes prison a more palatable experience. There should be no opportunity for illegal prison violence or black market because the inmates should never have any interaction with each other. The death penalty is wrong. It serves no useful purpose to society other than to satisfy some reptilian sense of revenge. No one should die to satisfy another's need for emotion.
Capital punishment is the most calculating, premeditated form of murder there is.
Because of court costs, it is not cheaper to execute a criminal than to keep them in jail for life. If execution were cheaper then I can think of no more despicable reason to kill someone than to save money. It is important to remove those individuals from our society who are too predatory and dangerous to live among us. But we do not have a collective right to take a life any more than an individual does. Christianity is not the State religion of the United States.