Interviewing Witnesses vs. Experts in Japan: What Are the Key Differences in Questioning Techniques for Eyewitnesses (e.g., Shoplifting) and Specialists (e.g., Doctors in Assault Cases)?

In any criminal investigation, information gathered from individuals other than the suspect—collectively known in Japan as "reference persons" (sankōnin, 参考人)—can be pivotal. These individuals might be eyewitnesses who directly observed the crime, or they could be experts whose specialized knowledge helps interpret complex evidence. While both provide crucial testimony, the approach Japanese investigators take to interviewing them, a process called sankōnin shirabe (参考人調べ), differs significantly based on whether they are eliciting factual recollections from an observer or seeking analytical opinions from a specialist.

This article explores these distinct questioning techniques, illustrating the methods used for eyewitnesses, such as a security guard in a shoplifting case, and for expert witnesses, like a surgeon who treated an assault victim.

Part 1: Interviewing Eyewitnesses – Reconstructing Observed Facts

When interviewing an eyewitness—someone who perceived events related to the crime through their own senses (sight, hearing, etc.)—the primary objective is to obtain a clear, detailed, and chronological account of their direct observations. The resulting written statement, a sankōnin kyōjutsu chosho (参考人供述調書), aims to be a faithful record of these perceptions.

Core Technique: Guided Narrative Based on Direct Perception

The fundamental approach to questioning an eyewitness mirrors the principles of a well-conducted direct examination in a courtroom setting. The process typically involves:

1. Initial Scene-Setting and Context:
   The interview often begins by establishing the witness's presence and role concerning the incident. For undisputed background facts, investigators might use concise, sometimes mildly leading questions to quickly establish context. For example, to a store security guard: "You were on duty as a security guard at [Supermarket Name] on the afternoon of August 15th when the alleged shoplifting incident involving Mr. [Suspect's Name] occurred, is that correct?" This confirms the witness's connection to the event and sets the stage.
2. Eliciting the Initial Observation (Open-Ended):
   Once the context is set, open-ended questions are used to prompt the witness's narrative.
   Investigator: "Please tell me, in your own words, what first drew your attention to the individual we are discussing that day."
   This allows the witness to start their account from their own perspective, highlighting what they deemed significant. For instance, a security guard might state: "The suspect caught my eye because they entered the store without a shopping basket and seemed to be wandering aimlessly in the beverage aisle, repeatedly looking around rather than selecting an item."
3. Chronological and Detailed Exploration:
   The investigator then guides the witness to recount events chronologically, probing for specifics at each stage.
   • "After you first noticed the suspect, what did you observe them do next?"
   • "You mentioned they picked up a juice and a can of coffee. What happened then?"
     The aim is to build a step-by-step narrative, focusing on the witness's direct sensory perceptions: "What exactly did you see the suspect do with those items?" "Did you hear the suspect say anything at that point?"
4. Use of Visual Aids (Diagrams, Maps, Photographs):
   When spatial relationships are important—such as the suspect's movements within a store, their position relative to the witness, or the location of CCTV cameras—using a diagram or map of the location is a crucial technique. The witness can be asked to mark their own position and the suspect's position at key moments.
   • For example, if a security guard saw a shoplifter conceal items: "I have a floor plan of the supermarket here. Could you please point out where the suspect picked up the juice and coffee? Now, could you indicate on this diagram where they moved to when you saw them place those items into their personal bag? And where were you positioned when you observed this?"
     This creates a much clearer and more objective record of the witness's spatial observations than words alone.
5. Clarifying Ambiguities and Probing for Detail and Rationale:
   Investigators will ask clarifying questions if any part of the witness's account is vague or needs further elaboration.
   • "You mentioned the suspect moved to an area you knew to be a 'blind spot' for the security cameras. How were you aware that particular spot was not covered by CCTV?"
   • If the witness confronted the suspect: "When you approached the suspect outside the store and said, 'You have unpaid items, don't you?', what was their verbal response? What was their demeanor?"
   • If the suspect offered an excuse: "The suspect claimed the items were purchased at another store. What was your reaction to that statement, given what you had observed?"
   • If the suspect later took actions that seemed contradictory: "You stated that while you were escorting the suspect to the office, they attempted to pay for the concealed items at a customer service counter. What did you understand them to be trying to achieve by doing that?"

The Investigator's Role with Eyewitnesses

With an eyewitness, the investigator acts primarily as a facilitator of memory, helping the witness to reconstruct their observations accurately and completely. The goal is to obtain a statement that reflects the witness's genuine recollection, free from suggestion or implanted information. As some Japanese investigative guides suggest, the interview process should be conducted as if the audio-visual recording of the interview itself (if made) could be presented in court as the witness's primary testimony.

Part 2: Interviewing Expert Witnesses – Accessing Specialized Knowledge and Opinions

Questioning an expert witness—such as a doctor, a forensic scientist, or an engineer—requires a different approach. The objective is not primarily to elicit a chronological narrative of observed events, but to understand and document their specialized analysis, findings, and professional opinions as they apply to the facts or evidence of the case.

Core Technique: Focused Inquiry Guided by Expertise and Prior Reports

1. Foundation on the Expert's Prior Work:
   Interviews with experts often revolve around a formal report or documentation they have already prepared, such as a medical examination report (shindansho, 診断書), a surgical record, a forensic analysis report, or a formal expert opinion document (kantei isho, 鑑定書).
   Investigator (to a surgeon): "Doctor, thank you for speaking with me. I'd like to discuss the surgical report you prepared concerning the treatment of Mr. [Victim's Name] following the assault on [date]."
2. Targeted and Focused Questioning:
   Unlike the broad narrative sought from an eyewitness, questions for an expert are typically more focused on specific aspects of their report, their methodology, the basis for their conclusions, or their opinion on particular issues relevant to the case.
   • "Doctor, your report mentions 'multiple penetrating injuries to the abdomen consistent with a sharp-edged weapon.' Could you elaborate on the specific characteristics of these wounds – their depth, trajectory, and the organs affected?"
3. Appropriate Use of the Expert's Own Documents:
   It is standard and accepted practice in Japan for an expert to refer to their own reports, medical charts, diagnostic images, or notes during an interview. This is not considered improper leading but rather a means to ensure the accuracy and completeness of their technical testimony, as experts deal with complex data and findings that may not be perfectly recalled without such aids. The investigator may actively direct the expert to specific sections of their documentation to facilitate discussion.
   • "Referring to page 3 of your report, where you describe the damage to the small intestine, could you explain the surgical procedure you undertook to repair this?"
4. Clarifying Technical Language and Complex Findings:
   A key role of the investigator is to ensure that the expert explains any technical jargon, complex scientific principles, or intricate findings in a manner that is understandable to non-specialists (i.e., prosecutors, defense attorneys, judges, and lay judges).
   • "You mentioned 'peritoneal contamination.' For the record, could you explain in simpler terms what that means and its potential consequences for the patient?"
5. Seeking Opinions on Case-Specific Evidence or Hypotheticals (within their expertise):
   Investigators will often ask experts to apply their knowledge to specific pieces of evidence from the case or to consider certain hypotheticals.
   • "Doctor, if these abdominal injuries, as you observed them, had been left untreated, what would have been the likely medical outcome for the victim, and over what timeframe?" (e.g., "Death from exsanguination or sepsis within hours.")
   • "The police recovered this knife [investigator might present a photograph or, if procedurally appropriate for a reference interview, the actual weapon safely packaged] which is alleged to have been used in the assault. In your professional opinion, are the characteristics of the wounds you treated consistent with having been caused by a weapon of this type and blade length?"
   • "Could the pattern of injuries you observed have resulted from an accidental fall onto a sharp object, or do they more strongly suggest a deliberate application of force with a stabbing motion?"

The Investigator's Role with Experts

When interviewing an expert, the investigator needs to have a sufficient foundational understanding of the expert's field to ask pertinent and intelligent questions. Their role is to:

• Ensure the expert’s complex knowledge is accurately translated into legally relevant and comprehensible information.
• Explore the basis, certainty, and any limitations of the expert’s opinions.
• Document the expert's analysis in a way that clearly supports or refutes specific aspects of the case.

Summarizing Key Differences in Approach

The Value of Recorded Interviews

While practical challenges sometimes exist, especially if an expert interview takes place at their own facility (as noted in some Japanese commentaries regarding equipment availability), the ideal scenario, as with other important interviews, would be to have an audio-visual recording. For eyewitnesses, it captures their demeanor and the spontaneity of their recall. For experts, it ensures an accurate record of complex explanations and opinions, minimizing the risk of misinterpretation when later drafting the formal written statement.

Conclusion: Tailoring Techniques for Optimal Information

Japanese investigators recognize that effective interviewing requires adapting techniques to the type of information being sought and the nature of the person providing it. For eyewitnesses, the approach is one of patient, chronological elicitation of directly perceived facts, much like a meticulous direct examination. For expert witnesses, it is a more focused dialogue, leveraging their specialized knowledge and often referencing their own detailed reports to clarify complex issues and obtain informed opinions critical to the case. By understanding and applying these distinct methodologies, investigators can obtain clear, credible, and legally potent statements from the diverse range of individuals who contribute to the fact-finding process in criminal justice.