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?
"By accident" is a difficult and often misused term. As I see it, there are at least three cases to consider:
- An outcome that was unforeseeable given the context and the behavior of the person involved
- An outcome that was foreseeable given the context and the behavior of the person involved, but for some reason was never considered
- An outcome that was foreseeable given the context and the behavior of the person involved, and was known to the person involved, but which the person risked anyway
Consider a professional juggler practicing his routine. Case 1 would be juggling in a practice room, where a ball might slip his hand, bounce off an unseen trampoline, and smash a window. Case 2 is juggling while walking down a city street, without considering that a slipped ball has a high chance of smashing some window. Case 3 is actively seeking out a display of window glass to practice next to, because the risk of smashing a window makes the practice more fun.
Children are generally considered to have deficits in foresight, so they aren't usually held responsible for the consequences of their behavior (aside from scolding and mild punishments meant to get them to use foresight). Adults are generally considered to have the capacity for foresight, and face consequences according to how foreseeable the outcome was. But morally coherent adults generally feel a sense of responsibility for the outcomes of their own actions, even if the outcome was truly unforeseeable. A morally coherent person who breaks a window pays to have it replaced.
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.
If someone does something by accident are they responsible?
Without considering their age you can say they are not responsible, if you can confirm whether that is by accident. But to make people aware of the importance of other people's lives and make them alert, except for children, such excuses should not be allowed in the society.