Based on the new Constitution, Criminal Procedure Law was radically changed toward the adoption of an adversarial system. Under this system, the roles of the police, the prosecutor, and the judge changed. Unfortunately, immediately following this innovation, a series of cases resulted in a miscarriage of justice partly because the police were not accustomed to the new system.[34]

Although a jury system came into force in 1939, it was practically never used because of inflexibility in the ongoing criminal justice system at that time. In addition, professional judges have always enjoyed a high level of trust in Japanese society. After the war, the police began to carry guns instead of sabers, according to the advice of the United States