Is a person considered sinful and obligated to offer expiation if his father died after being injected with medication for cancer treatment, and air bubbles unintentionally entered the vein, knowing that the father was in an advanced stage of the illness?

It is necessary to consult doctors to determine the cause of death. If three trustworthy doctors confirm that the cause of death was the entry of air through the injection, then the person responsible must pay the blood money (diyya) to the heirs (unless they pardon him) and offer expiation for accidental killing, which is freeing a believing slave. If he cannot find one, then he must fast for two consecutive months. The blood money is to be paid by the 'aqilah (male relatives on the father's side) of the person responsible. However, if the doctors state that the entry of air was not the cause of death, then he is not liable for anything.