If the police don't take the time to do it right, then the chance for mistrial is elevated. Now wouldn't that be a travesty?
My point, that our legal system requires so much expensive documentation for a trial when it is clear only one shooter was invoved. If there had been even one report of some armed citizen having retured fire in self defense.. I could see a extensive investigation to make sure someone wasn't hit by friendly fire. But that wasn't the case here. Or at Columbine either.