It is true that fulfillment of rights and settlement of disputes in declaring crimes and submitting complaints based on Criminal Procedure Act is one of the duties entrusted with judges, but to succeed in this regard discovering the truth and fact is necessary. It is not always easy for judges to reach this end and it requires cooperation and collaboration of competent experts who are fully equipped with relevant skills and technologies to help judges to achieve the final objective, i.e. administration of justice. The forensic medicine is one of the most important members of this group, which stands first in Criminal Procedure Act because of benefits derived from its specialty and opinion. The Criminal Procedure Act of1392, through which the legislators endeavored to be up-to-date and remove the shortcomings of the previous Act, provides for involvement of forensic medicine in criminal prosecution and different stages of the proceedings, including detection of crime, prosecution of the accused, detention, trial, sentencing and enforcement of the punishment. This study attempts to show the role considered by the mentioned Act for forensic medicine in each one of the mentioned stages and effects of its opinions in the decisions made by the judicial authorities. It is clear that the role of the forensic medicine in law is more than just presence and to give advice in criminal procedure and other fields of this science such as civil law, Criminal law, etc, benefit from the forensic medicine in fulfiling their duty of administering justice. Of course, dealing with these issues requires related research efforts.                                                 .