C.S.Lewis has an excellent essay somewhere about the real basis of our penal system. It is retribution. He says that retribution is the only really just reason for the punishment of criminals, and the only reason that is fair and brings dignity to the human person.
First of all, retribution is not the same thing as revenge. Retribution is a just punishment which suits the crime. It has no other aim but to allot to the criminal the proper consequence for his action.
‘Civilized’ people confuse retribution with revenge and consider it to be a barbaric form of punishment, and in many primitive societies it is barbaric. The thief has his hand cut off. The rapist is castrated. The murderer executed, etc. However, the principle of retribution need not be barbaric. A civilized society with a fair judicial system and a network of prisons can mete out retribution in a fair and equable way.
The other motives for punishment, Lewis points out, seem humane, but lean intrinsically to injustice. So, for example, one might have rehabilitation as a motive for punishment. However, if rehabilitation is the motivation do we keep the criminal locked up until he is sufficiently reformed and rehabilitated? If so, a petty criminal might have to be locked away far longer than a murderer for a murder of passion might be repented of and the prisoner reformed quite quickly whereas a petty burglar may never be reformed. Shall he be locked away until he is a changed man? That would be unjust.
The same thing applies for the motivation of protecting the public from dangerous criminals. Shall we lock a criminal away simply for that motivation? If so, we may have to lock a person up for life even if he has committed no crime, but because he threatens to do so. Again, the wrong motivation for punishment leads to injustice.
Rehabilitation and protection of the public are beneficial side effects of punishment, but they cannot be the motivation for punishment.
Retribution is not only more objective and fair, but it also is based on the dignity of the human person. This because it takes human choice seriously and metes out a just and predetermined consequence for a person’s chosen action. This is not sentimental, nor is it bound by false motivations for punishment.
If retribution is the proper basis for the punishment of criminals, then some will argue that the death penalty is demanded. “An eye for an eye and a tooth for a tooth.” One who has taken a life should give his life. Perhaps. But then, there are many ways that a life may be taken. Life imprisonment is also a way that a life may be taken.
What the criminal does with his life in prison is another discussion altogether, but if the purpose is retribution, then a way for him to make reparation would be built into the occupation of his time behind bars. A severe punishment like solitary confinement or hard labor may be the retribution most appropriate rather than execution.