First off, why exactly are you letting the USBP guide you in moral principles and not the Church? Just because the USBP has certain beliefs regarding the death penalty, that doesn’t mean they’re taking the correct moral position.
We should not listen to any group other than the Church for moral guidance. However, the Catechism and everything since has always made the subject one of prudence. Indeed, since the Church has historically supported the right to the death penalty, looking at what has changed is the only way to no longer support it. At the heart of the debate for the Catholic is whether or not it is still needed to keep society safe. If you do not gather information from experts in the field, then there is no data on which to base an intellegent opinion.
I post on this topic because I have dealt with criminals for 20+ years, It surprises me how naive some people are. I have come to realize that most people behind bars are really no all that bad. They have made a few bad choices, usually early on in life, and it has resulted in behavior that hurts others.
There is a very small minority, though, that are such total sociopaths, that they will be a danger to the lives of those around them in any environment. It is possible that they could be housed safely until their natural death, but not in America. Not with our constitution and progressive interpretation of the constitution. Not while allowing contact with family, or any freedom, priviledge or right at all.
Take away all the rights of such people and give carte blanche to those housing them to do whatever necessary to keep them away from society, they could be housed in a dungeon-like environment. Otherwise, those who believe that we can safely house all murderers, be they posters are popes, are mistaken.