What should a person who caused someone's death in a car accident do?

If the accident occurred without any negligence on the part of the person, then there is no guarantee (compensation) required of him, nor any expiation (kaffarah). However, if it was due to unintentional neglect or dereliction, then two things are incumbent upon him: expiation (emancipating a believing slave or fasting for two consecutive months), and blood money (diyyah) to be paid to the heirs of the deceased, which is borne by the 'Aqilah (the male relatives on the father's side). Such cases should be referred to the Sharia courts.