The purpose of the criminal justice system is to deal with criminals by punishing them.However, in some cases, instead of the actual criminals, innocent individuals are convicted for a crime. The main question of this study is to consider the mechanisms of the criminal justice system to improve the unfair and inaccurate result of trail. Reopening trail, which is a mechanism that Iran's legal system, like many other countries, has predicted. However, some procedural restrictions such as laps of time, make problem to hear all claims of innocence. Actually, there will be innocent convicts who never will get the opportunity to prove his/her innocence. After conviction, criminal justice system assumes the conviction is completely true. Hence, it does not find itself responsible so much. Few countries, have special system includes commission and procedure to consider the claims of innocence. finally, the role of non-governmental organization and innocence movements in this connection is undeniable.