Self-defense as one of the justified causes of crime or the reason to drop retaliatory punishment (death penalty) has been defined and legislated by the legislator according to articles 156, 302 and 303 of the Islamic Penal Code 1392. Iran's legislature has sought to develop the substantive provisions of legitimate defense and increase its scope from real to extreme and apparent types in the articles of reference. Despite this, in the field of formal rules governing this legal institution, especially the authority that determines it, according to the majority of judges, especially in the prosecutor's office, it has lacked the necessary clarity and courage, and even with the approval of Article 265 of the Criminal Procedure Law, the ambiguity is doubled and the judicial procedure in terms of the possibility of intervention and the exercise of legitimate defense by the prosecutor's office, it has confused and adopted taste. By adopting the qualitative method and extracting the approaches of Iran's criminal justice system through field investigation and in-depth interviews, the present research seeks to answer the basic question of what harms may cause from the acceptance of legitimate defense in the prosecution in cases of intentional homicide and the strategies to overcome the existing challenges. The result of this research shows that not only the discretion in the exercise of legitimate defense and the investigation of its complex conditions is beyond the power of the prosecution and the unit investigation authority and it has serious and effective challenges, but with the above mentioned legal texts, validity is determined by the Criminal Court and the prosecutor's office does not have the legal competence, authority and discretion to accept it. In this way, the public meetings and judicial decisions and consultative opinions of the legal department of the judiciary, which is under the jurisdiction of the prosecutor's office in the exercise of legitimate defense with any party and has taken steps to stabilize the prevailing judicial thought and practice, are against the legal standards and the belief of the judges of the Criminal Court and the Supreme Court of Iran.