1. Accusatorial and Adversarial Systems of Criminal Trial

When you hear the term "criminal trial," you might assume the following: the trial's purpose is to uncover the truth; so all the evidence and materials gathered by the police and prosecution during the investigation are submitted to the court in advance; the judge goes through these investigative files before hearing cases from both the prosecution and defense, and plays an active and leading role in bringing out the "truth" at trial. This image of a criminal trial is somewhat closer to the non-adversarial (inquisitorial) system adopted by countries in Continental Europe. The current Japanese law, however, primarily adopts different systems of criminal trial: the accusatorial system and the adversarial system, both of which originate from the Anglo-American countries, such as England and the United States.^[1] In a Japanese trial, the prosecutor--the one who formally brought the accusation of a crime against the defendant to court--must prove the crime specifically alleged in the charging document beyond a reasonable doubt, building the case from the ground up. The defendant has no obligation to assist the prosecution in proving its case but is granted a full opportunity to rebut and challenge the accusation. The judge (or panel of judges, which may include the lay-judges) acts much like a neutral referee: the judge will pronounce the defendant guilty if the crime asserted in the charging document is proven beyond a reasonable doubt based on the evidence and arguments presented and contested by the parties; otherwise, the judge will pronounce an acquittal. The judge is not provided with the investigative files and relies only on the evidence submitted in open court. The judge may not find the defendant guilty of crimes not specified in the charging document nor rely on facts not fully contested by the parties--even if the judge personally believes them to be true.

A criminal trial based on the accusatorial and adversarial systems can be understood as a forum to test the prosecution's case by subjecting it to thorough scrutiny and criticism from the defendant. The fundamental idea of such a forum is that, before punishing a person, the person's side of the story must be thoroughly heard, and a full debate must occur between the prosecutor--representing the state and society--and the person over the reason for punishing him or her. This process is important to ensure careful fact-finding, especially to avoid punishing the innocent. More fundamentally, for a criminal penalty to carry the meaning of condemning wrongdoing and possess individualized legitimacy and fairness, it is essential to secure circumstances where even the person being punished can reasonably be expected to accept it as just. This is why, no matter how obvious the defendant's guilt may seem, there must be the thorough process of hearing and overcoming the defendant's case before imposing any punishment on him or her.^[2]

2. Importance of Discovery in Modern Criminal Trials

In a criminal trial based on accusatorial and adversarial systems, it is essential that the defendant can fully build and present his or her case against the prosecutor's case. One of the most important measures in modern criminal trials in this regard is the prosecutor's disclosure of evidence to the defendant. For one party to allow the other party to inspect and copy evidence and materials--typically those in its possession--is called discovery. However, it was once a prominent view that discovery does not align with the "adversarial" system because it involves assisting the opposing party. Indeed, in England and the United States, where the adversarial system developed, discovery was not very common until the mid-20th century, as it had long been thought that each party was responsible for gathering the necessary evidence and materials. However, this was likely because, in times when people lived in small, close-knit communities and witness testimonies were often the primary method of proof, it was not considered too difficult for defendants to form and develop their case based on their own knowledge and the charging document. Today, society has become significantly urbanized, and people are highly mobile and anonymous. There are now far more methods of proof than before. It is not uncommon for defendants to lack sufficient evidence, materials, and information to surmise the evidence the prosecutor will introduce to prove their guilt, decide what defense they should pursue, and develop a convincing case. Consequently, it has come to be recognized that the prosecution should allow the defendants to access evidence and materials collected through its powerful investigative power, leading to a significant expansion of criminal discovery in both England and the United States.

What is more important to the concept of the adversarial criminal trial is not requiring the parties to gather evidence independently, but enabling the defendant to fully present his or her case, thereby avoiding miscarriage of justice and ensuring the legitimacy and fairness of punishment when the defendant is found guilty. Disclosing evidence to the defendant should be understood as a measure that serves the aims of the adversarial system and as an act expected of the prosecutor, who represents the state and society and whose duty is to engage in meaningful debate with the defendant to achieve those aims.^[3]

3. Constitutional Right to Discovery

In the United States, it is considered a constitutional right of a defendant to receive disclosure of any material evidence favorable to him or her. This is called the Brady rule, named after the landmark 1963 Supreme Court decision.^[4] Under the Court's current interpretation of this rule, the prosecutor has the due process obligation to disclose evidence if its disclosure has a "reasonable probability" of changing the outcome of the trial, whether regarding the defendant's guilt or sentence. This obligation applies even when the defendant did not request its disclosure or when the evidence is held only by the police^[5]. As the defendant's conviction or sentence will be overturned if the prosecutor fails to fulfill this obligation, the Brady rule is one of the most significant principles governing the practice of discovery throughout the United States.^[6]

The rationale behind the current Brady rule can be understood as follows: the prosecutor, who is a representative of the state and society, has a special duty to ensure the fairness of the trial and, in particular, to avoid miscarriage of justice; if, despite this duty, the prosecutor allows a trial to result in an unreliable outcome containing a realistic risk of a miscarriage of justice by failing to disclose evidence favorable to the defendant, the unreasonableness of this failure rises to the level of a due process violation. This rationale should apply with the same force in Japan, which adopts the accusatorial and adversarial systems, defines the prosecutor as a "representative of the public interest"^[7], and interprets due process as being guaranteed under Article 31 of its Constitution. It seems reasonable to assume that, under Article 31, Japanese prosecutors have the same constitutional duty to disclose evidence as their counterparts under the Brady rule.^[8]

4. Discovery in the Pretrial Arrangement Procedure: Process and Concerns

The disclosure of evidence during the "pretrial arrangement procedure" plays a key role in Japanese criminal discovery. This procedure is a conference held after the prosecutor files the charging document and is completed before the trial sessions begin. Its purpose is to facilitate productive trial sessions in a continuous, systematic, and efficient manner by organizing the issues and evidence in advance.^[9] In this procedure, the prosecutor discloses evidence in three steps. The first step involves the disclosure of evidence the prosecutor intends to introduce at trial. The second step involves the disclosure of evidence that is important for assessing the probative value of the prosecutor's evidence to be introduced, and that falls into specific categories.^[10] Discovery in these steps aims to provide the defense with a full picture of the prosecutor's case and allow the defense to assess its strengths and weaknesses, thereby helping the defense shape its own case. The defense is then required to disclose its planned arguments and evidence it intends to introduce. By doing so, the defense may obtain discovery of evidence that relates to its planned arguments.^[11] This third step of discovery is aimed at disclosing evidence that supports the defense's arguments and also evidence that helps the defendant further specify or modify its case. By reshaping its case and presenting it to the prosecutor, the defense may have further evidence disclosed that relates to its revised arguments.

This stepwise system of discovery is carefully designed to provide sufficient evidence to help the defense to form and develop its case while, at the same time, avoiding unnecessary disclosure in order to prevent adverse effects it can cause--such as excessive disclosure of the privacy of those involved, delays in proceedings, and increased burdens on the parties and the courts. For the same reason, the second and third steps of discovery require, among other things, the defense to identify the evidence for which it requests disclosure. While the purpose is legitimate and the system appears to function well in most cases, there is a concern that the defense might not gain access to evidence simply because it was unaware of its existence in the prosecution's files and failed to request its disclosure--particularly concerning is when this results in the non-disclosure of favorable evidence. In part to address this concern, the prosecutor is now required, upon the defense's request, to share a list of evidence in the prosecution's files, following the 2016 amendment to the Code of Criminal Procedure.^[12] Nevertheless, since the list is rather simple and is not required to provide specific details or summaries of each piece of evidence, the risk still remains that the defense might not be able to make specific discovery requests for important evidence. If we consider that Article 31 requires the prosecutor to disclose evidence to the same extent as the Brady rule, the prosecutor has a constitutional duty to disclose evidence without any request by the defense, provided its disclosure carries a reasonable probability of affecting the trial's outcome. Even when the evidence does not meet this constitutional threshold, the prosecutor should consider informing the defense of it if the evidence would impact the probative value of the prosecutor's evidence to be introduced or would support the planned arguments of the defense, and if the defense would most likely have requested its disclosure had it been aware of its existence or details.^[13] Such a practice would be appropriate in preventing accidental non-compliance with constitutionally required disclosure and in ensuring the innocent is not punished and the defendant's case has been fully heard and overcome when the defendant is found guilty.

---

[1] See, Toyo Atsumi, Zentei Keiji Sosho-ho [Criminal Procedure: Fully Revised], 2d ed. 6-11 (2009).
[2] See, chapters 6-13 in Toyo Atsumi, Tsumi to Batsu wo Kangaeru [Thinking about Crime and Punishment] (1993).
[3] See, Sho Miake, Prosecutor's Duty to Disclose Exculpatory Evidence under Article 31 of the Japanese Constitution, 123 Chuo L. Rev. no. 9/10, 166-67 (2017)
[4] See, Brady v. Maryland, 373 U.S. 83 (1963).
[5] See, Kyles v. Whitley, 514 U.S. 419, 432-38 (1995).
[6] Although there are criticisms regarding the effectiveness of the Brady rule in the United States, it is noteworthy that various measures and discussions have been undertaken to ensure its compliance.
[7] Article 4 of the Public Prosecutor's Office Act.
[8] See, Miake, supra note 3, at 170-72.
[9] See, Article 316-2 of the Code of Criminal Procedure.
[10] See, Articles 316-14 and 316-15 of the Code of Criminal Procedure. Examples of evidence disclosed during the second step of discovery include written statements made by witnesses during the early stages of the investigation, whom the prosecutor intends to call at trial.
[11] See, Article 316-20 of the Code of Criminal Procedure. Unlike in the second step of discovery, evidence in this step is not required to fall into a specified category.
[12] See, paragraph (2) of Article 316-14 of the Code of Criminal Procedure.
[13] See, Miake, supra note 3, at 173.

Sho Miake／Associate Professor, Faculty of Law, Chuo University
Area of Specialization: Criminal Law

Sho Miake was born in 1984. He graduated from the Faculty of Law, Chuo University. He completed the Master’s and Doctoral Programs in the Graduate School of Law, Chuo University. He holds a Ph.D. in law. After serving as an Associate Professor at the Graduate School of Law, University of the Ryukyus, he joined the Faculty of Law at Chuo University in 2023.

His research focuses on criminal discovery and U.S. criminal procedure.

His main written works include;
Novel Approaches in Criminal Discovery in the U.S. States: Open-File Discovery in North Carolina, 24 Komazawa L. & Pol. Sci. Rev. no.1, 43 (2024)
The Recent Developments in the U.S. to Ensure Brady Compliance, 129 Chuo L. Rev. no.6-7, 273 (2023)
Prosecutor’s Duty to Disclose Exculpatory Evidence under Article 31 of the Japanese Constitution, 123 Chuo L. Rev. no.9-10, 159 (2017).

• Share articles
• 
• 
•