The death penalty or capital punishment is the state execution of a criminal, whose crime is so grave that the death penalty proportionally redresses the disorder inflicted on society by the crime.
The Catechism of the Catholic Church in paragraph 2266 teaches, "Legitimate public authority has the right and duty to inflict punishment proportionate to the gravity of the offense. Punishment has the primary aim of redressing the disorder introduced by the offense."
This point was reiterated by Pope St. John Paul II, who in his 1995 encyclical, Evangelium Vitae, taught, "The primary purpose of the punishment which society inflicts is 'to redress the disorder caused by the offence.' Public authority must redress the violation of personal and social rights by imposing on the offender an adequate punishment for the crime."
Besides exacting adequate expiation or retribution for the crime, society's criminal punishment is also for the purpose of rehabilitating the criminal, defending society against the danger posed by the criminal and deterring other criminals from committing similar crimes. In the same encyclical, John Paul II exhorts that "except in cases of absolute necessity," if these ends can be met without executing the criminal, then the death penalty should not be invoked. "Today, however," said the pope, "as a result of steady improvements in the organization of the penal system, such cases are very rare if not practically non-existent."
Catholics can disagree on when to apply the death penalty in various societies. In 2004, one year before becoming pope, Cdl. Joseph Ratzinger, as head of the Congregation for the Doctrine of the Faith, relates:
If a Catholic were to be at odds with the Holy Father on the application of capital punishment or on the decision to wage war, he would not for that reason be considered unworthy to present himself to receive Holy Communion. ... There may be a legitimate diversity of opinion even among Catholics about waging war and applying the death penalty.
Understand common misconceptions surrounding capital punishment in The Download—The Death Penalty.