Throughout the series Nolan struck true to Batmans rule of no killing. Sure, leaving Ras Al Ghul to die pushes the limits of this, but fans were happy to let that slide because of how cool the line I won't kill you, but I don't have to save you was. This moral was only amped up with his confrontation with the Joker; at multiple times, even after Rachels death and Harveys disfigurement he couldn't do it. There was considerably less opportunity for killing for most of Rises and yet this was the one where the rule was broken. When trying to turn the truck towards the reactor, Batman is reduced to bombarding it with rockets, killing the driver. This also leads to Mirandas death, although thats defendable as it was her bad driving under gunfire, rather than the bullets themselves that did it. But theres no denying killing the truck driver. Although I guess brushing over it is better than that god awful scream from DCs other noble hero. I suppose it all proves Jokers line the only sensible way to live in this world is without rules and tonight you're gonna break your one rule, given how it leads to the only way Bruce Wayne can truly live, but boy is that tenuous.