Yes, and in that case, where that penalty serves to protect all innocent people from them, then that is my view also, and also the Church's view. It is only in the case that innocent people cannot be protected from such criminals, that the Church teaches that the death penalty is warranted, permitted, encouraged and even required. If for example such a monster has influence outside their prison, then they should be killed.
That is my view, but again, this is off-topic, since I'm posing the position that in no case should we kill criminals, and asking what the Church should do in such a world.