The fact that she alleges he did it once, then told her a dirty joke, then did it again tells me that dementia is likely not a factor.
You would be wrong.
Alzheimer’s patients have no filter. So when they see a pretty girl (or guy for the women) they might well make a comment THEY NEVER WOULD HAVE MADE in the rest of their life. My poor mom will try to hug the pool man three times in a 2 minute conversation. They need to be kept away from people sometimes. Their sex drive sometimes is still there but like a severely mentally challenged adult, they need to be controlled. My mom doesn’t sexually assault but she tries hugging men every chance she can. Just like an overly friendly adult with severe mental challenges. They are now in that category of “not fit to stand trial” and they ont remember any of it 3 minutes later anyway, so they are unable to witness even for themselves.
They are truly no longer responsible for their actions and the “assault” is the fault of the caregiver.