Still, I believe the death penalty, because of its finality, is more feared than imprisonment, and deters some prospective murderers not deterred by the thought of imprisonment. Sparing the lives of even a few prospective victims by deterring their murderers is more important than preserving the lives of convicted murderers because of the possibility, or even the probability, that executing them would not deter others. Whereas the life of the victims who might be saved are valuable, that of the murderer has only negative value, because of his crime. Surely the criminal law is meant to protect the lives of potential victims in preference to those of actual murderers. Threats and punishments are necessary to deter and deterrence is a sufficient practical justification for them.
Retribution is an independent moral justification.
Although penalties can be unwise, repulsive, or inappropriate, and those punished can be pitiable, in a sense the infliction of legal punishment on a guilty person cannot be unjust. By committing the crime, the criminal volunteered to assume the risk of receiving a legal punishment that he could have avoided by not committing the crime. The punishment he suffers is the punishment he voluntarily risked suffering and, therefore, it is no more unjust to him than any other event for which one knowingly volunteers to assume the risk. Thus, the death penalty cannot be unjust to the guilty criminal.