And you don't think that if this assault actually took place, and the police viewed the cctv tape as claimed, that they would have said something about it?
The story, as told here, just doesn't ring true.
I think maybe you are not being told the whole story by your brother, for whatever reason.
Perhaps you need to sit down with your brother before rushing off to solicitors or whoever and find out what it was all really about. Could save any embarrassment later on.