On the other hand, I see the game as a matter of choices and consequences.  This means that a truly accidental killing by magic isn't a violation, since that isn't a choice.  The player may want to change an aspect, but that's up to the player.

It also means that the decision to use excessive and potentially lethal force against a human is a choice, and can have consequences.  Harry is well aware that he has very powerful magic, and worries about what might happen when he uses it.  I don't want the wizards in my campaign throwing full-power spells around casually.

This doesn't mean that a player gets blindsided by a First Law violation.  The player should always get warning of some sort.  In our first session, one wizard hit a thug with a full-power spell, and the thug was slammed against the wall and collapsed to the floor, unconscious and bleeding.  There's no Law against injuring somebody with a spell, but that's a suggestion that excessive magical force might kill.  Nor would I allow a violation without pointing out, before the roll, that that magic might kill somebody.

I'm less concerned with the exact game mechanics here.  By a strict interpretation of the rules, a character could nuke an NPC and declare that the NPC got a bad concussion, or possibly banged up by bouncing around in that refrigerator.  I don't think that makes a good game, though.