False accusations can actually be the result of prior abuse. They may substitute one person for another. Or do things as a result of mental illness caused by abuse. Kids think differently to adults and may behave inexplicably. And unfortunately that means that an abused child is a terrible witness.
I was abused as a child (not sexually however) and I can attest to this. Many of my memories are highly charged and don't really hold up - they're very confused. Some of the scariest stuff that happened to me I don't even remember, and my siblings have had to let me in on it (and they were even younger at the time).
As a child you're really not prepared for the concept that your parents are treating you badly. So that realization doesn't come until much later.
