It is Catholic teaching that crime merits punishment in this life and as well as the next, and that the State has authority to administer appropriate punishment, including the sentence of death.

There are four reasons for the State levying any penalty:

Rehabilitation. The sentence of death can and sometimes does move the condemned person to repentance and conversion.

Defense against the criminal. It obviously prevents the wrongdoer from committing future crimes. Whether execution is necessary is a prudential judgment, but modern penal systems in some countries have made it rare for execution to be the only means of defending society.

Deterrence. The evidence on deterrence is ambiguous.

Retribution. Guilt calls for punishment. The graver the offense, the more severe the punishment ought to be. And by consenting to the punishment of death (e.g., the “Good Thief”) the criminal can expiate his evil deeds and escape punishment in the next life.

Heinous crimes may require death.