How could a priest prove he is innocent of sex abuse charges, other than if he was out of the state or country at the time?

I know of a priest (who is actually a Monsignor) who was recently accused and found guilty by the Archdiocese for abusing a boy on one occasion 40 years ago.

The priest is 85 years old so he was forced to retire and is currently in a nursing home. Of course he says he didn’t do it and he is determined to clear his name.

The Archdiocese doesn’t have the same standard as criminal court, so they can find someone guilty with whatever protocol they want to.

It’s totally understandable why they can’t have someone with these accusations continue as a priest and having access to children. It’s also totally understandable why the Archdiocese doesn’t want to appear to be tolerant of priests with terrible accusations such as sex abuse of children. I’m not in any way defending priests who abuse children and I’m not critical of the Archdiocese for finding priests guilty, using whatever means they want to.

I’m just wondering how someone could prove their innocence, in a case like this, other than if they were out of the state or country at the time.