>>1708952It might come from a different understanding of justice.
When a criminal is punished, it's not primarily a mater of using punishment as a deterrent to others that might be temped to commit the same crime. That comes second to the debt that the offender now owes to the person who was wronged. This also leads to the conclusion that the plaintiff should be able to forgive the defendant (although, often the plaintiff is the common people).
In the case of murder, prison may deter others, but the victim is still owed justice from the murderer that no amount of money or incarceration can pay. The murderer stole the life from the victim, and this can only be re-payed by the life of the murderer.
This, of course, is only for completely certain cases. Death should never be made mandatory by law since it's too hard to be sure of guilt sometimes.
