An Expert Witness Guide to Justice Systems: Japan 

By Noah Bolmer

Japan’s approach to expert witnesses (sometimes called “expert advisors”) is shaped by its broader legal architecture: court-centered, document-driven, and restrained. Experts are appointed to assist the judge rather than the parties, and their findings are typically submitted in writing rather than presented through testimony. The process is formal but not theatrical. There is rarely cross-examination, limited party involvement, and little room for strategic framing.   

Judicial Structure and Expert Involvement 

Japan’s legal system, grounded in civil law, places judges at the center of the evidentiary process. Across civil, criminal, and administrative matters, judges determine the scope of inquiry, manage the pace of litigation, and decide when specialized knowledge is required. This orientation shapes how proceedings unfold and how expert input is evaluated. 

The system is organized into three primary branches: 

• Civil courts resolve disputes between individuals or organizations. 

• Criminal courts handle violations of the penal code. 

• Administrative courts address conflicts involving government agencies or public law. 

Judges are career professionals selected through the National Bar Examination and trained at the Legal Training and Research Institute, a centralized institution operated by the Supreme Court. Their responsibilities extend beyond legal interpretation to include oversight of fact development and procedural integrity. This structure informs the treatment of expert witnesses, who are engaged to support the court’s understanding of technical matters. Their findings are typically submitted in writing, with oral testimony and cross-examination reserved for cases where the judge requests clarification. 

Japan’s use of expert witnesses emerged during the country’s legal modernization in the late 19th century. Following the Meiji Restoration in 1868, Japan undertook sweeping reforms to align its legal institutions with western models, drawing heavily from German civil procedure. The Japanese Civil Code of 1896, part of a broader codification effort, introduced judicial authority to appoint experts when cases involved technical questions beyond the court’s own knowledge. Unlike France, which formalized expert involvement through a royal ordinance in the 17th century, Japan integrated expertise gradually through statutory development. There was no centralized registry or formal guild of experts. Instead, courts drew from academic and professional communities as needed, using judicial authority to manage their input. 

This historical trajectory continues to shape Japan’s approach today. Expert involvement is usually initiated by the court, and party-retained experts, while permitted, are rare and subject to procedural constraints. Attorneys, known as bengoshi, advise clients, present legal arguments, and respond to technical findings. They offer legal interpretation within a framework set by the court, rather than directing the presentation of facts or examination of witnesses. 

Court-Appointed Experts 

Japanese courts often specialize in specific types of disputes, ranging from IP to Bankruptcy. The judges are well-versed in their practice area, but there are occasions where technical minutiae or exceptional circumstances require the use of an expert. Once the court determines that specialized input is necessary, it selects an expert from academic, scientific, or professional circles. There is no formal registry or licensing body for experts, so judges rely on institutional networks and prior experience to identify qualified individuals. The appointment is governed by procedural codes, which authorize the court to pose specific technical questions and receive written responses. These reports are expected to be objective and narrowly focused on the issues defined by the judge. Oral testimony is rare and typically reserved for clarification. 

Investigations may involve site visits, document review, or interviews, depending on the nature of the case. The expert works independently but within the scope of the court’s mandate, and their findings are incorporated into the case record. Attorneys may respond to the report or request further explanation, but they do not direct the expert’s inquiry. The emphasis remains on clarity and neutrality, with the court managing both the scope and presentation of technical evidence. 

In serious criminal cases, lay participation is introduced through the saiban-in system—a mixed panel of three professional judges and up to six citizens who deliberate together on the verdict and sentencing. Judges guide the process and ensure legal standards are upheld, while lay members contribute to factual deliberation. When expert input is required, the court-appointed model remains intact. Reports are submitted to the full panel, and if testimony is needed, judges lead the questioning. Attorneys may pose follow-up questions, but cross-examination is limited even when present. The expert’s role is explanatory, serving the entire panel rather than any individual party. This structure reinforces the system’s commitment to procedural discipline and impartial expertise, even in cases involving public participation. 

Privately Commissioned Experts 

While parties in Japan may submit expert opinions of their own, these are rarely central to the court’s analysis. The judiciary retains full discretion over whether to admit such input, and party-commissioned reports are generally treated as supplementary. Their purpose is to raise questions, offer alternative interpretations, or highlight potential gaps in the court-appointed expert’s findings—but they do not carry equal procedural weight. 

If a party disagrees with the conclusions of a court-appointed expert, they may request permission to submit a counter-report. This is roughly analogous to a rebuttal report in adversarial systems, though its impact depends entirely on whether the court finds it credible and relevant. Judges may consider the alternative analysis, especially if it identifies methodological flaws or introduces overlooked data, but they are not required to engage with it in depth. The court’s own inquiry remains primary, and any external input is filtered through that lens. 

This dynamic reflects the broader structure of Japanese litigation, where technical evidence is managed by the court and advocacy is channeled through legal argument rather than evidentiary contest.  

Scope Definition and Oversight 

When a Japanese court appoints an expert, it issues a directive that defines the technical questions to be addressed and outlines the boundaries of the inquiry, although it may revise or expand the scope if new questions arise. The expert is expected to investigate independently, using methods appropriate to the subject matter while remaining focused on the specific issues identified by the judge.  

The report is submitted in writing and becomes part of the case record. It is shared with both parties, who may respond or request clarification. Communication between the expert and the parties is limited and typically mediated by the court. Informal contact is discouraged, and the expert is not expected to meet with either side or engage in direct correspondence. This structure preserves procedural neutrality and ensures that the expert’s findings are presented in a controlled and transparent manner. 

By defining the inquiry and managing its presentation, the court maintains oversight without interfering in the substance of the expert’s analysis. The process is designed to clarify technical issues within a judicial framework, supporting the court’s fact-finding responsibilities while minimizing the risk of advocacy or procedural ambiguity. 

Payment and Cost Allocation 

Expert compensation is managed through code and judicial procedure. The court determines the fee based on the complexity of the inquiry, the time required, and the nature of the expertise. One or both parties may be ordered to advance the cost, depending on who initiated the request or how the issue arose during proceedings. These payments are treated as litigation expenses and may be reimbursed under cost-shifting rules if the initiating party prevails. 

Experts do not negotiate terms with the parties. All financial arrangements are handled through the court, which ensures that payment remains proportionate and neutral. There is no standardized fee schedule; rates vary according to the expert’s field and the demands of the case. This structure reinforces the expert’s role as a technical resource and prevents financial influence from shaping the scope or tone of the analysis. 

Structural Contrast with the U.S. Model 

The Japanese and American systems share a formal expectation of expert neutrality, but the mechanisms for ensuring it differ significantly. In the United States, experts are typically retained by one of the parties and presented as part of that party’s case. Although they are legally required to offer objective opinions, their testimony is often shaped by strategic framing and subject to adversarial scrutiny. Cross-examination is central to the process, and the court relies on opposing counsel to challenge the expert’s credibility, methodology, or conclusions. 

In Japan, experts are appointed by the court and serve as technical resources for the judiciary. Their findings are submitted in writing and reviewed by the judge, not presented as partisan evidence. There is no expectation of cross-examination, and party-appointed experts—while permitted—are rarely central to the court’s analysis. The structure is designed to minimize contest and preserve procedural clarity. The court defines the inquiry, manages the presentation, and evaluates the findings without relying on party-driven critique. 

Sidebar: Japanese System Features 

• Document-Only Trials For minor offenses, trials (called “summary proceedings”) may proceed entirely on paper. No courtroom appearance, no oral arguments, just written submissions reviewed by a judge. If uncontested, the case is resolved without a hearing. 

• Lay Judge Panels Serious criminal cases may be heard by mixed panels of professional judges and citizen lay judges. These lay judges deliberate, vote, and help determine both guilt and sentencing. It’s not a jury, but it’s not purely judicial either. 

• Solo Interrogations Suspects are often questioned without a lawyer present. While legal counsel is permitted, it’s not guaranteed during interrogation, and many suspects face extended questioning alone. Sessions may be lengthy, unrecorded, and conducted over multiple days. 

• 99.8% Conviction Rate Japan’s conviction rate is famously high, but it reflects prosecutorial discretion more than judicial bias. Prosecutors tend to pursue only cases they are confident they can win, and many are resolved before trial. 

Conclusion 

The Japanese approach to expert evidence reflects a commitment to judicial control and restrained advocacy. Expertise is less a tool for persuasion than a useful resource for the court. The near-absence of cross-examination, limited role of party-appointed experts, and emphasis on written reports all point to a system that manages expert input through judicial oversight, not adversarial exchange. 

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