What is the verdict established by Shariah for a person who killed another person in a car accident and the victim's relative forgives the killer?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

A person who accidentally kills another person has to do two things:

First: Pay Ad-Diyah which is blood-money (compensation) to be given to the family of the deceased. But if they forgive the killer then the compensation is dropped as in your case. The blood-money is valued at 1,000 coins of gold, or 12,000 coins of silver, or the equivalent of this in notes or 100 camels.

Secondly: An expiation is due when killing accidentally, if the killer is able to do so. The order of the expiation is as follows:

1  1) To free a believing slave.

2  2) If the killer is unable to free a believing slave, then he has to fast for two consecutive months.

The evidence for this is the saying of Allaah (interpretation of meaning): {And whosoever kills a believer by mistake, (it is ordained that) he must set free a believing slave and compensation (blood money, i.e. Diyah) be given to the deceased's family, unless they remit it. If the deceased belonged to a people at war with you and he was a believer; the freeing of a believing slave (is prescribed), and if he belonged to a people with whom you have a treaty of mutual alliance, compensation (blood money - Diyah) must be paid to his family, and a believing slave must be freed. And whosoever finds this (the penance of freeing a slave) beyond his means, he must fast for two consecutive months in order to seek repentance from Allaah. And Allaah is Ever All-Knowing, All-Wise.}[4:92].

A Muslim is not considered a disbeliever by killing another Muslim or killing a non-Muslim person, whether deliberately or accidentally. However, if someone kills deliberately, he/she has indeed committed a major great sin.

Allaah knows best.