Regardless of the crime that has been committed, capital punishment is unacceptable in the modern world, Pope Francis stressed in a recent letter.

"Nowadays the death penalty is inadmissible, no matter how serious the crime committed," the Pope said.

"It is an offence against the inviolability of life and the dignity of the human person, which contradicts God's plan for man and society, and his merciful justice, and impedes the penalty from fulfilling any just objective. It does not render justice to the victims, but rather fosters vengeance."

Pope Francis' words came in a letter to Federico Mayor, president of the International Commission against the Death Penalty. The Pope held an audience with a delegation from the commission March 20.

In his letter, he reflected on Church teaching, based on Scripture and thousands of years of experience, in defending the sanctity of human life from conception to natural end. He noted that this respect for life is based on human dignity of persons made in the image of God.

"For the rule of law, the death penalty represents a failure, as it obliges the state to kill in the name of justice," he said, adding, "Justice can never be wrought by killing a human being."

"With the application of the death penalty, the convict is denied the possibility to repent or make amends for the harm caused; the possibility of confession, by which a man expresses his inner conversion, and contrition, the gateway to atonement and expiation, to reach an encounter with God's merciful and healing justice," Pope Francis continued.

He noted that capital punishment is often "used by totalitarian regimes and groups of fanatics for the extermination of political dissidents, minorities, and any subject labelled as 'dangerous' or who may be perceived as a threat to its power or to the achievement of its ends."

Pope Francis has spoken out against the death penalty several times since his election two years ago. His predecessors, Pope Benedict XVI and Pope John Paul II, also spoke out against its use in modern society.

The Catechism of the Catholic Church teaches that the death penalty may be used "if this is the only possible way of effectively defending human lives against the unjust aggressor." However, it adds, such cases today "are very rare, if not practically nonexistent."

In his letter, Pope Francis reflected on this concept.

"On some occasions it is necessary to repel an ongoing assault proportionately to avoid damage caused by the aggressor, and the need to neutralize him could lead to his elimination; this is a case of legitimate defense," the Pope said.

"However, the presuppositions of personal legitimate defense do not apply at the social level, without risk of misinterpretation," he continued, explaining that the death penalty is applied not for a current act of aggression, but for one committed in the past.

Additionally, he said, the death penalty is applied to those who are not currently able to cause harm, since they have already been "deprived of their liberty" and the threat that they pose has therefore been neutralized.

In addition to the use of the death penalty, Pope Francis said, "States kill...when they send their people to war or when they carry out extrajudicial or summary executions. They can also kill by omission, when they fail to guarantee to their people access to the bare essentials for life."

He also warned that "life imprisonment entails for the prisoner the impossibility of planning a future of freedom, and may therefore be considered as a sort of covert death penalty, as they deprive detainees not only of their freedom, but also of hope."

The Pontiff encouraged members of the International Commission against the Death Penalty to continue their work, "so that the action taken against this cruel punishment may be successful and fruitful."

"The death penalty is contrary to the sentiment of humanitas and to divine mercy, which must be the model for human justice," he stressed.

"There is discussion in some quarters about the method of killing, as if it were possible to find ways of 'getting it right'…But there is no humane way of killing another person."