Reasons for modifying the teaching, the paragraph says, include: the increasing effectiveness of detention systems, growing understanding of the unchanging dignity of the person, and leaving open the possibility of conversion.
The Community of Sant'Egidio, an association that represents Christians in 70 countries and a long-time campaigner against the death penalty, expressed "joy" at the move.
What has it changed from?
Church leaders pointed out that the Pope Francis' action builds on work begun by St. John Paul II, who spoke of the dignity of guilty and innocent life and described executions as cruel and unnecessary.
In it, he made two arguments that specifically spoke to the American context: The death penalty is illegitimate because many convictions have later been found to be in error and have been overturned, and because executions of prisoners in some states have been badly botched.
Hamilton, the University of Pennsylvania professor, said the pope's decree could be hard for the devout - especially in a climate where evangelicals and Catholics are increasingly arguing that their faith controls everything they do. Amnesty International does not publish data from China, where the death penalty is also legal.
"In defending the abolition of the death penalty, one does not forget the suffering of the victims involved, nor the injustice that has been perpetrated".
The church's new teaching will likely feature prominently in the confirmation process for Supreme Court nominee Brett Kavanaugh, who, if confirmed, would bring the total number of Catholics on the bench to five.
In Paris also welcomed the intention of the Catholic Church to abolish the death penalty worldwide.
New York Governor Andrew Cuomo announced this week that he will be introducing legislation that aims to permanently remove the death penalty from New York State law, following a recent decree by Pope Francis that the death penalty is "inadmissible in all cases". Turkey had ended the punishment in 2004 in an effort to join the European Union. "Today, in fact, as a effect of the possibilities which the state has for effectively preventing crime, by rendering one who has committed an offense incapable of doing harm - without definitely taking away from him the possibility of redeeming himself - the cases in which the execution of the offender is an absolute necessity 'are very rare, if not practically nonexistent'".
It was precisely Francis' citation of the Gospel, however, that sparked criticism from some on the Catholic right, who cited Scripture in arguing that Francis had no authority to change what previous popes taught. A significant proportion of Catholics in the United States are immigrants, many of them Hispanic. "Wala. So my death penalty for high-level trafficking is not anti-poor", Sotto said.