I am a practicing Catholic who has read the BIble first to last 4 times...and went to Catholic schools and know the rules...
*The Pope cannot change any doctrine inspired by the HOly SPirit and which was proclaimed "Ex Cathedra"(Officially spoken from the chair of Peter).This Pope says many strage things off the cuff, but unless he speaks Ex Cathedra, it is only his thought process and we are not bond by it.

*The Pope should consult HIS BOSS, whose word is reflected in Holy Scripture..." an eye for an eye, a tooth for a tooth" extrapulates to a life for a life.

*Right at the start, Gen.7:6; Whosoever sheds the blood of man, his blood shall be shed.

*All thru the Mosaic law capitol punishment is referenced in Exodus and Deut.

*And Paul in the NT, Romans, says to remember the roman law of the sword and we are subject to the civil law