This always confused me if a child breaks a vase the parents say "Well it's an accident it's not your fault.". Assuming the person is not negligent if someone does something bad like break a vase or kill someone in a car accident should they be fined or thrown in jail?
From a moral point of view, you could argue that the person is innocent, because they had no intent to do something bad.
But suppose a little child dashes out in front of your speeding car, and you kill her. Even if it's an accident that no one could have avoided, you may still be prosecuted, even if you aren't ultimately convicted.
This may be an example of "setting an example." The state doesn't want people to think you can kill someone with your car and just walk away after saying, "Oops, sorry!" It's a serious matter.
Now, suppose that you're driving 35 mph in a 30 mph zone when you kill a child. Or suppose you had just one glass of wine before you got in your car.
We might still call it an accident. But if you were technically operating outside the law, the dead child's parents may not be in a forgiving mood.
Whether or not this addresses your question depends on how you define "responsible." If you're convicted of murder - even if you were driving within the speed limit - then the state obviously thinks you're responsible.
But whether or not you're responsible at some higher ethical or philosophical level is matter of debate.
If it happened to me, I'd probably be saddled with guilt for the rest of my life. But, at the same time, I'd cut myself a little slack, knowing that there are far worse drivers out there. I might curse myself for my bad luck. Why couldn't someone else have been driving down that road when that child dashed into the street?
I don't see how personal feelings of guilt or the bereaved parents mood are relevant. Assuming the truth of your example that there was no negligence involved, then the accident is precisely that - a turn of fate.
"From a moral point of view, you could argue that the person is innocent, because they had no intent to do something bad" . From both a moral and a legal point of view.