If he is in protective services has a councillor seen him as they know how to speak and figure out the truth if there has been anyabuse. Ask her some questions about the person who was abusive has she got that right, who else is around her?if she is saying that what makes your Husband think he didnt do it?
It's quite possible it's not true - sometimes victims tell what happened, but name the wrong perpetrator.
Has he actually had lots of physical access to her when no one would notice? Has anyone else had physical access to her?