My thoughts on this:
As has been said, the death penalty in principle is acceptable. Many theologians, many popes, and even Scripture has said that. Accordingly, when to apply the death penalty is not a matter of morality, but rather prudence. I personally do not think that we ought to totally outlaw the death penalty for extraordinary cases. There will always be some extraordinary case that would require the death penalty. I think, however, that it is only once every few years in all the United States, if not the world (at least in societies with modern prison systems). In my ideal society, in order for the death penalty to be applied, the case would have to meet some minimum requirements:
- It is proven beyond a reasonable doubt that the accused committed the crime.
- The crime was a severe violation of someone’s person (along the lines of murder or rape).
- It can be reasonably deduced that the criminal is willing to commit the crime—or similar heinous crimes—again. (i.e. the criminal “repented” before, but committed the same or similar crimes again, or the criminal admits that they would do it again given the opportunity)
- It can be reasonably deduced that today’s prison system will not be able to prevent the criminal from doing it (or similar heinous acts) again. (I think that 99% of the time, the only people that can escape today’s prisons are those who have many resources from the outside.)
I have yet to come up with more specific requirements. (i.e. What exactly constitutes “severe” in condition two?)
Again, in my ideal society, it would require the jury to unanimously decide that these conditions are met. Then, it ought to go before some sort of board of people with experience in the justice system. They would have to agree that these conditions are met, with the exception of condition one, since that is what the jury is for. They would be given the facts of the case alone, with no names or any other identifying information. (“the guilty,” “the victim,” “witness
a,” “location
b,” etc.) If the board agrees that conditions two to four are met, then the death penalty will be used, after the criminal is given an opportunity to be baptized or go to confession. After probably about ten years, the board would go back over the case with all information available. They would again determine if all conditions were met, including condition one. If the answer is no, they would be required to determine what went wrong, and the society’s legislature would be required to pass legislation amending the process before doing anything else. Eventually, the process would be as perfect as humanly possible.
In addition to this, the prison system would be required to go through a similar process of reform every few years, so that condition four is met as little as possible. Another board (possibly of psychologists/psychiatrists) would attempt to determine what caused the person to commit the crime(s), and could require the legislature to pass legislation to fix the problem if it could justly do so.
EDIT: I have come up with another requirement. If the guilty acted due to mental illness, the mental illness could not be dealt with sufficiently.