According to the Islamic criminal law, it is necessary for the perpetrator to be an offender and to have criminal liability in the presence of conditions and elements including the condition stipulated in the Article 140 of the Islamic Penal Code, approved in 1392. Based on this Article, the perpetrator should be wise and mature. What is important in this regard is the question as to what is the ruling if we doubt whether a person is wise or mature during a crime? Some of the jurisprudents, knowing that the rule of Dar̕ is applicable to the Qisas, hold that there should be no retaliation, and some others hold that the rule of Dar̕  is specific to the crimes with prescribed punishments (Had). They have set the principle of istishab as the criterion of action, however they have also different ruling by reasoning to the principle of istishab. The authors have used a descriptive-analytical method in the present research. Not generalizing the principle of Dar ̕to Qisas, they took an approach to the viewpoint of Imam Khomeini and relying on the principle of istishab, in the case of doubt in the criminal maturity they absolutely believe in the precedence of the word of the criminal. And in the case of doubt in the criminal madness, if his/her insanity is evident from the very beginning of his birth, they absolutely believe in the precedence of the word of the criminal, but in the case when his/her insanity is accidental and only the date of the murder turns out to be promising, the word of his/her guardian is precedent and in other cases the word of the criminal is precedent. If the criminal does not have a history of insanity, the word of his/her guardian is precedent.