Is it reasonable to expect people to know that? If I'm below that level, what are the odds of me knowing the law well enough to know that it doesn't apply to me?
Do you think this applies in general to questions of legal liability, or is this one unique? If it's unique, why should anyone think that this case is unique? If you think in general it's "not hard" to know things about legal liability, either you're Elle Woods or you're an extremely overconfident fool.
