At the heart of Catholic teaching on the death penalty is the belief that " Human life is sacred because from its beginning it involves the creative action of God and it remains for ever in a special relationship with the Creator, who is its sole end…” (Catechism, No. 2258).
Regarding the death penalty, the catechism of the Catholic Church was updated in 2018:
“2267. Recourse to the death penalty on the part of legitimate authority, following a fair trial, was long considered an appropriate response to the gravity of certain crimes and an acceptable, albeit extreme, means of safeguarding the common good.
Today, however, there is an increasing awareness that the dignity of the person is not lost even after the commission of very serious crimes. In addition, a new understanding has emerged of the significance of penal sanctions imposed by the state. Lastly, more effective systems of detention have been developed, which ensure the due protection of citizens but, at the same time, do not definitively deprive the guilty of the possibility of redemption.
Consequently, the Church teaches, in the light of the Gospel, that “the death penalty is inadmissible because it is an attack on the inviolability and dignity of the person”, and she works with determination for its abolition worldwide.
 FRANCIS, Address to Participants in the Meeting organized by the Pontifical Council for the Promotion of the New Evangelization, 11 October 2017: L’Osservatore Romano, 13 October 2017, 5.
Pope Francis on the Death Penalty
February 8, 2018 Letter to the Bishops regarding the new revision of number 2267 of the Catechism of the Catholic Church on the death penalty
Other Statements by Pope Francis
“It is impossible to imagine that states today cannot make use of another means than capital punishment to defend peoples’ lives from an unjust aggressor … All Christians and people of good will are thus called today to struggle not only for abolition of the death penalty, whether it be legal or illegal and in all its forms, but also to improve prison conditions, out of respect for the human dignity of persons deprived of their liberty.” International Association of Criminal Law Address 10/24/2014
"Nowadays the death penalty is inadmissible, no matter how serious the crime committed. 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…”
“The death penalty is contrary to the sentiment of humanitas and to divine mercy, which must be the model for human justice. … 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…”
“Dear friends, I encourage you to continue with your work, as the world needs witnesses of God's mercy and tenderness, and may the Lord Jesus grant the gift of wisdom, so that the action taken against this cruel punishment may be successful and fruitful". International Commission Against the Death Penalty Address 3/20/2015
Death Penalty Resources
Catholic Bishops of Ohio Teaching Statements on the Death Penalty