I can't really see how he's going to fight this with a view to be sucessful.
Say for instance, April walked off with MB and fell in the river and met her fate, if MB hadn't have asked her to walk with him, she wouldn't have been there and her being five years old isn't in a position to realise the potential danger she might be in, so even if MB physically didn't 'help' her in the water he is still responsible for the situation that occurred- April being lured to a situation which lead to her death, if that makes sense.