The line is drawn at intent and purpose, regardless of state of mind. If I lose control of my car (if I had a car) and killed a child on the sidewalk it would be an accident and not deserving the death penalty for there was no intent or purpose to kill that child. On the other hand if I get out of my car, walk up to the child, and strangle him to death, there would be clear intent and purpose of me killing the kid, thusly the death penalty would/should apply.