The deliberate killing committed by a minor or by someone who is insane is treated as accidental homicide, for neither of them possesses intent; they are therefore comparable to a legally responsible person who errs.

Killing by indirect causation is likewise treated as accidental—for example, when someone digs a well or a hole in a roadway, or leaves a vehicle standing in a dangerous place, and a person is thereby killed.

Accidental homicide entails two obligations. First, the expiation is paid from the killer’s own wealth: he must free a believing slave; if he cannot find a slave, or finds one but cannot afford the price, he must fast two consecutive months. Second, the diyyah (blood money) is borne by his ʿaqilah, namely the male members of his agnatic clan.

If someone kills a Muslim who is standing in the ranks of the unbelievers, thinking him to be an unbeliever, only the expiation is required, for the Almighty says: “Whoever kills a believer by mistake must set free a believing slave and pay blood money to the victim’s family, unless they remit it as charity. But if the victim belonged to a people at war with you yet was himself a believer, then a believing slave is to be freed. And if he belonged to a people with whom you have a treaty, then blood money must be paid to his family and a believing slave set free. Whoever cannot find one must fast two consecutive months in repentance to Allah; and Allah is All-Knowing, All-Wise” (Q. 4:92).

Thus the Quran divides cases of accidental killing into two categories:

1. A category in which the expiation is upon the killer and the diyyah upon his ʿaqilah—that is, when a believer is killed by mistake outside the enemy ranks, or when the victim belongs to a people with whom we have a pact.
2. A category in which only the diyyah is due, namely when a believer is killed while among the unbelievers because the killer presumed him to be an unbeliever.