Despite the right to legal counsel in prosecution process before the court and tribunals mentioned through international documents and legal systems and/or the necessity of the presence of legal assistance being recognized during the investigations and prosecutions nationally (according to article 48 of criminal procedure law of Iran) and internationally (according to international related documents such as International Covenant on Civil and Political Rights), execution of this right is practically challenged by the legal ambiguities. On one hand the criminal procedure is a mean in the judge’s hand in order to prove the facts; and on the other hand, it is a tool for persons to defend their rights and freedoms. Since many of judicial decisions about the person is based on the documents, which are gathered through facing the police, depriving the suspect from legal assistance will increase the possibility of his her rights suppression. During recent years, in both national legal systems and international criminal court’s procedure several changes have occurred accordingly. This article analyzes the mentioned changes through national law and also the procedure of international criminal courts, and introduces achievements of comparative law regarding how to balance between ensuring the right to legal counsel through tribunals and investigations and establishing a fair trial. The article will hereof study and criticize the failure of Iran’s legal system according to the international standards of fair trial.