This study aims to explore the discretion of the police and prosecutors during the pre-trial stage based on six systems of criminal justice: England and Wales, the United States, France, Germany, Japan, and South Korea. In criminal proceedings, discretion plays a significant role in supplementing as statutes cannot provide for every circumstance. In particular, at the pre-trial stage, public prosecutors can conclude their cases by exercising considerable discretion. Such discretion differs depending on the jurisdiction. The differences demonstrate distinctive prosecutorial roles. Based upon these findings, I propose that in general, the public prosecution service plays a filtering role. Unlike other jurisdictions, in Korea the prosecutors act as monopolists. However, justice cannot be achieved by the monopoly of one legal actor in the criminal proceedings.