I would think that while a priest would not be obligated to to divulge what he heard in a confession or who had confessed to him, the priest could freely admit that he never heard the confession of one who was trying to cause that priest some mischief, especially if that individual had never made any confession to him or had any sort of contact at all.
“While I doubt that very many of those who are pedophiles go to confession and admit it to their priest, I have no doubt that more than a few Irish pedophiles who are caught after this bill passes will swear they confessed their crimes to several priests.”
As I understand it, absolution for a crime often requires turning yourself in for it. If they don’t intend to do so I don’t think they can be absolved of it.