I was in a tournament as a new (visiting) player and the guy I was playing was known for his moves. In one close hit situation, he played the shot at break speed even though that made no sense for position. He claimed there was no way to see which ball was hit first, which was technically true. (The simple physics said it was a bad hit.) Fortunately, the room owner was watching and called the foul, so there was no more "earnest discussion."It seems like it would be too hard to call. If it is definitely undecidable, the call goes to the shooter. If you were refereeing a game and the shooter shot much harder than need be, would this change your call?