Actually you're the first to try this argument. That's like saying it doesn't matter how GZ got on the ground because we have a dead teenager that he shot. We don't know how the physical confrontation began, and that is relevant as TM may have felt he was acting in self defense. It is very easy to imagine circumstances leading to that event, which does not make them true, but does make them reasonable possibilities only countered by the word of GZ. Get it?