Pope Francis called Wednesday for categoric opposition to capital punishment to be written into an update of the most important guide to Catholic teaching.
His comments, which will be controversial with many fundamentalist Christians and some Catholics, came in a speech to clerics attending a conference in Rome to mark the 25th anniversary of the publication of the Catechism of the Catholic Church.
The catechism is a question and answer guide to what Catholics should think about a wide range of moral and social issues.
Acknowledging that the Vatican itself had historically had "recourse to the extreme and inhuman remedy" of judicial execution, Francis said past doctrinal errors should be put aside.
"We have to restate that, however grave the crime that may be committed, the death penalty is inadmissible because it attacks the inviolability and the dignity of the person," he said.
The execution of a human being was fundamentally against the teachings of Christ because, by definition, it excluded the possibility of redemption, he argued.
The Catholic church has steadily increased the strength of its opposition to the use of capital punishment in recent years.
Pope John Paul II made an appeal for a global consensus on abolition in 1999 and Francis's predecessor, Benedict XVI issued a similar call in 2011.
The 1992 text of the catechism says authorities should take appropriate measures in the interest of the common good without excluding the use of the death penalty in extremely grave cases.
More recent updates say justifying circumstances are now rare if not practically inexistant. And a version of the catechism aimed at younger people now includes a question, "Why is the Church opposed to the death penalty?"
Francis has made clear his own personal opposition to the death penalty on numerous occasions.
"It doesn't give justice to victims, but it feeds vengeance," he said in June 2016, arguing that the biblical commandment "thou shall not kill," applied to the innocent as well as the guilty.
© 2017 AFP