If someone tries to rescue someone from a burning roof, slips, drops them, and they die, we don't class them as a murderer. This is because we believe that judgements should be based on the intention behind an action, not the outcome. Whether or not we like to admit it, however, our moral judgements are sometimes shaped by mere luck. Imagine someone gets into a car while drunk and drives home. We all agree that's bad. Now imagine another person who does the same, but this person kills a pedestrian. We naturally think that this action is worse. But surely the only difference is that the first driver got lucky, while the second driver was unlucky. The second driver did not intend to kill a pedestrian any more than the first did.