This study aims to examine the ruling on killing an insane person, whether sane or insane, comparing Islamic law with Iraqi law. This will help us understand the views of Islamic schools of thought and Iraqi law on the issue, their evidence, and how to deal with an insane killer. The study focuses on key topics, namely retaliation (qisas), blood money (diya), expiation (kaffarah), as well as common murder between sane and insane people and cases of intermittent insanity. This study adopts the descriptive-analytical approach, a comparative study of the views of Islamic schools of thought and Iraqi criminal law, highlighting the evidence and points of agreement and disagreement between jurisprudence and law, and explaining how to deal with an insane person on this issue. Jurists agree, contrary to the opinion of some Malikis, that retaliation is not imposed on an insane person, given their lack of legal responsibility due to the absence of the basis of legal capacity, which is reason. This is the predominant opinion and is consistent with Iraqi law. The majority of jurists believe that the guardians of an insane person must pay blood money, and this is the predominant opinion, contrary to the Zahiri school of thought and Iraqi law. The majority of jurists require expiation for murder by an insane person, which is the more correct opinion, contrary to the Hanafi, Zahiri, and Iraqi law. Concerning periodic insanity: In Islamic law, whoever is definitely insane is subject to the same rulings as an insane person and to the same rulings as a sane person while still sane, by consensus. As for Iraqi law, the insane person is handed over to the medical committee. If the saneness of the perpetrator is proven during the crime, he is subject to the same rulings as a sane