The Saiban-in (Lay Judge) System — Fundamental Case Law

Introduction

The Saiban-in Seido (Lay Judge System) is Japan’s system of citizen participation in criminal justice, introduced by the Act on Participation of Lay Judges in Criminal Trials (Saiban-in no Sankasuru Keiji Saiban ni Kansuru Hōritsu) in 2004 and implemented in 2009. The system represents a fundamental reform of Japanese criminal procedure, replacing the pre-war jury system that had fallen into disuse and introducing a new model of mixed lay-professional adjudication.

The constitutional status of the Saiban-in system was confirmed by the Supreme Court’s Grand Bench decision in the Saiban-in Act Constitutionality Case (Saiko Saibansho, Grand Bench, November 15, 2011), which upheld the system against challenges based on the right to a fair trial and judicial independence.

Historical Background

Japan’s first experiment with citizen participation in criminal justice was the Jury Act (Baishin Hō) of 1923, which introduced a jury system for serious criminal cases. Under the Act, juries of twelve citizens decided questions of fact, and the judge decided questions of law and imposed sentence. However, the Act contained a provision allowing the defendant to waive the right to a jury trial, and prosecutors and defendants alike increasingly exercised this option. The jury system was suspended in 1943 during the Second World War and was not revived after the war.

For over sixty years — from 1943 to 2009 — Japanese criminal trials were conducted exclusively by professional judges. The absence of citizen participation in criminal adjudication was criticised on several grounds: the lack of citizen oversight of judicial decision-making, the distance between the judiciary and the public, and the extremely high conviction rate (over 99%), which critics attributed to the insularity of the professional judiciary.

The movement for judicial reform gained momentum in the 1990s, culminating in the Justice System Reform Council (Shihō Seido Kaikaku Shingikai) report of 2001, which recommended the introduction of a lay judge system. The Saiban-in Act was enacted in 2004 following a period of public consultation and legislative deliberation.

Structure of the Saiban-in System

Composition of the Panel

For each eligible case, a panel is composed of six lay judges (saiban-in) and three professional judges. The lay judges are selected randomly from the voter registration list of the district where the trial is held. Persons with certain disqualifications — including those with criminal convictions, members of the Diet, lawyers, and judges — are ineligible.

Eligible Cases

The Saiban-in system applies to serious criminal cases where the maximum penalty is death or life imprisonment. These include:

• Intentional homicide (murder)
• Robbery causing death
• Arson of an occupied building
• Kidnapping for ransom
• Dangerous driving causing death
• Offences involving illegal drugs where the accused is charged as a repeat offender
• Certain cases of assault causing death

The 2024 revisions to the Saiban-in Act expanded the list of eligible cases to include additional offences, including certain organised crime offences and cases involving the production of counterfeit currency.

Functions of the Panel

The lay judges and professional judges decide both guilt and sentence jointly. They deliberate together, and all panel members — lay and professional — have equal voting rights on all issues. The verdict and sentence are decided by a majority vote, with the requirement that the majority must include at least one professional judge. This requirement ensures that no verdict or sentence can be imposed without the concurrence of at least one professional judge.

The Saiban-in Act Constitutionality Case (2011)

The constitutionality of the Saiban-in system was challenged in the Supreme Court in the Saiban-in Act Constitutionality Case (Saiko Saibansho, Grand Bench, November 15, 2011). The defendant, convicted of murder and robbery-homicide in a Saiban-in trial, argued that the system violated several provisions of the Constitution.

The Constitutional Challenges

The defendant advanced three principal arguments:

Violation of Article 37 (Right to a Fair Trial): The defendant argued that the participation of lay judges — who lacked legal training and experience — violated the right to a fair trial. Specifically, the defendant contended that the lay judges could not properly apply the rules of evidence, evaluate complex legal arguments, or maintain the requisite objectivity.

Violation of Article 80 (Judicial Independence): The defendant argued that the lay judges, as ordinary citizens temporarily serving as judges, lacked the constitutional guarantee of judicial independence that protects professional judges from external influence.

Violation of Article 31 (Due Process): The defendant argued that the Saiban-in system violated the principle of due process because the selection process for lay judges did not provide adequate procedural protections.

The Supreme Court’s Holding

The Supreme Court Grand Bench unanimously upheld the constitutionality of the Saiban-in system.

On the fair trial argument, the Court held that the Constitution does not require that all participants in a criminal trial be legally trained. The participation of lay judges enhances the fairness of the trial by bringing “common sense and social experience” to the adjudicative process. The Court emphasised that the professional judges provide legal guidance to the lay judges, that the lay judges are selected from a broad cross-section of the population, and that the defendant has the right to challenge a lay judge for cause.

On the judicial independence argument, the Court held that Article 80’s guarantee of independence applies to the court as a whole, not to individual judges. The participation of lay judges does not compromise the independence of the court because the lay judges are subject to the same duties of impartiality and confidentiality as professional judges and are protected from external influence.

On the due process argument, the Court held that the selection process — which includes opportunities to challenge the panel composition and to disqualify individual lay judges — satisfies the constitutional requirement of due process.

Impact of the Saiban-in System

The introduction of the Saiban-in system has had a significant impact on Japanese criminal justice.

Higher Conviction Rates

The conviction rate in Saiban-in trials has been consistently high (over 95%), though slightly lower than the rate in professional-only trials (over 99%). This has been attributed to the careful screening of cases by prosecutors, who are more likely to decline prosecution in marginal cases that would be tried before a mixed panel.

Longer Sentences

Sentences imposed in Saiban-in trials have been, on average, longer than sentences imposed in comparable professional-only trials. This is particularly notable in murder and rape cases, where Saiban-in panels have imposed sentences at or near the statutory maximum more frequently than professional judges alone.

Other Effects

The Saiban-in system has also led to:

• Simplification of trial procedures: Trials are conducted more efficiently to accommodate the lay judges’ schedules
• Increased use of plain language: Lawyers and judges use simpler language to ensure that lay judges can follow the proceedings
• Greater emphasis on victim impact evidence: The prosecution presents more victim impact statements and evidence of the harm caused by the offence
• Improved public understanding: The system has increased public understanding of and engagement with the criminal justice system

The 2024 Revisions

The Saiban-in Act was amended in 2024 to expand the list of eligible cases and to make procedural adjustments based on the experience of the first fifteen years of operation. The revisions included:

• Expanding the list of eligible offences to include additional serious crimes
• Introducing new provisions to protect lay judges from harassment and intimidation
• Clarifying the rules for jury sequestration and deliberation
• Improving the support services for lay judges

Conclusion

The Saiban-in system represents a fundamental transformation of Japanese criminal justice. The shift from a purely professional judiciary to a mixed lay-professional model of adjudication has brought greater citizen participation, enhanced transparency, and increased public trust in the criminal justice system. The Supreme Court’s decision in the Saiban-in Act Constitutionality Case confirmed the constitutional validity of the system and affirmed the legitimacy of citizen participation in the administration of justice. As the system continues to evolve through legislative amendment and judicial interpretation, it stands as one of the most significant institutional reforms in modern Japanese legal history.