This article by Steve Skojec from his site One Peter Five. It details the reasons for the death penalty in Catholic teaching. Please read it carefully.
In light of today’s news that the pope has “changed the Catechism of the Catholic Church about the death penalty, saying it can never be sanctioned”, we are reprinting this as a reference point for concerned Catholics. – SS, 8/2/2018
When the first version of this column was originally published in March, 2015, it was occasioned by comments made by Pope Francis to the effect that the Death Penalty is never justified. Since then, it has become necessary to revise and update it, due to additional comments on the topic from the pope. Of particular note, these appeared in his apostolic exhortation Amoris Laetitia (83), which states: “the Church not only feels the urgency to assert the right to a natural death, without aggressive treatment and euthanasia”, but likewise “firmly rejects the death penalty”.
You can read the rest here: https://onepeterfive.com/pope-francis-wrong-death-penalty-heres/