Judging Witness Credibility: Essential Techniques for Investigative Interviews
In the high-stakes world of corporate investigations, witness statements are often key pieces to the investigative puzzle. While physical and documentary evidence provide fragments of a story, a few credible witness accounts can weave those fragments into the compelling narrative that resolves an investigation. But how do we know if witnesses are being truthful?
The key word here is “credible.” How many times have we heard “he said/she said,” or “he said/they said” statements, and we are left to determine credibility?
Here are some established approaches used to assess witness credibility:
Behavioral Analysis
Assessing credibility requires careful listening to the words of a witness, however, it also demands a detailed behavioral analysis. Investigators should closely observe verbal and non-verbal behaviors (NVB) of a witness.
Verbal behavior includes changes in speech patterns. These changes can indicate whether a witness is becoming more comfortable or uncomfortable. When a witness repeats a question back to an interviewer or answers a question with a question, these changes are important to note because it is very common for a person to do this to buy time to formulate a response or deflect the question.
Investigator: “Where were you last night at 10pm?”
Witness: “Where was I last night?”
Investigator: “Where were you standing in the room when your supervisor walked in?”
Witness: “Does that matter? Did you ask other people where they were standing?”
Of course, be mindful that it is possible a witness did not hear your question clearly, or perhaps for a witness whose first language is not English, the witness may not have fully understood your question, so they are trying to get clarification. If there is a pattern that is not explained by a language or hearing barrier, there may be a credibility problem.
Another example of a shift in speech pattern includes dissociation. Often a witness who has experienced a traumatic event will dissociate when describing the event, emotions related to the event, or the aftermath. One tell-tale sign of dissociation is shifting from the first person (“I” and “me”) to the second person (“you”) or even third person (“one” or “someone”). This happens involuntarily because it is too emotionally painful for the witness to reconnect themselves with the event. During the Johnny Depp vs. Amber Heard trial, Johnny Depp dissociated during portions of his testimony that were particularly traumatic to him, such as when he testified Ms. Heard threw a glass bottle at him and it broke on impact, severing his finger.
At time marker :40 he begins to talk about the incident using “I.” At 1:06 he mentions that the bottle thrown by Ms. Heard “made contact” instead of “hit me” or “hit my finger.” Again at 2:13 he mentions he was looking at “the meaty portion of the inside of your finger.” While he does testify in the first person for the majority of this testimony, the places where he dissociates makes his testimony more credible because trauma such as one’s spouse severing their finger can cause one to shift into the second or third person when recounting the traumatic events.
Dissociation can also sound like this:
Investigator: “When did he begin hitting you?”
Witness: “After I was pushed onto the couch, he began hitting my legs with a pipe.”
Investigator: “What did you do when he started hitting you?”
Witness: “Well, you just want it to stop, you start thinking about how to get away, and if someone would hear you if you screamed.”
Dissociation is an indicator of credibility because without trauma, a witness most often stays in the first person when recalling what they observed or experienced. As with any indicator of credibility, dissociation is not determinative of credibility, but it is indicative. An astute investigator will note any change in speech pattern.
Non-verbal behavior (NVB) such as body language is also important to assessing credibility. NVB includes facial expressions, changes in a witness’ skin (flushing, going pale, or sweating) and how a witness holds his, her, or their body while communicating. Many of these NVBs are not voluntary, and they may vary by culture, age, gender, or even disability – either physical or mental, including neurodivergent witnesses who may process questions differently or be more or less expressive than what is considered neurotypical.
Eye contact is a great starting point for assessing NVB, however, it must be considered in a broader context than the interview. In some cultures, prolonged eye contact is deemed to be intimate or invasive, so it would not be reasonable to expect a witness to look you directly in the eyes when answering questions. The witness may be uncomfortable with you looking directly at them or looking directly at you.
Changes in a witness’ skin can also flag a credibility problem. However, like eye contact, investigators should observe any changes to skin in a broader context. Are the witness’ cheeks flushed pink, bright red, or blotchy? Are hives or a rash appearing? Are veins bulging in the witness’ forehead or neck? Is the witness sweating lightly? Profusely?
Many people may experience these changes just from the anxiety or “nerves” that accompany being questioned in any investigation, but it can also occur because of the psychological response behind panic, fabrication, concealment, or denial. NVBs may be evidence of a “fight or flight” response.
Other NVBs include whether a witness is fidgeting (clicking pens, jangling pocket change, biting nails), has crossed arms or legs, is turned towards you or away from you, whether the witness’ head is tilted down, up, or to the side, and even facial expressions such as the position of the eyebrows, squinting, wincing, ticks, tears, or changes in the rhythm of the witness’ breathing.
By intentionally and attentively assessing witness behaviors, investigators can draw inferences about the reliability of the witness’s testimony.
Corroboration (Cross-Verification)
Corroboration involves cross-checking a witness's testimony with other evidence. If a witness’s account aligns with independent, verified sources, the testimony is considered highly reliable. For instance, if a witness claims to have seen a tall figure enter an office around 9 PM, and video footage shows a similar figure entering at 9:22 PM, the testimony is corroborated. Conversely, if the footage shows the figure entering at 4:17 PM or not at all, the testimony is less reliable.
Corroboration helps validate testimony by filling in gaps in the storyline and disproving previously accepted information. An investigative timeline is a crucial tool to determine what corroborating evidence may be available to gather prior to witness interviews.
Structured Information Gathering
When it comes to structuring these interviews, there must be a method to the madness. Effective interviews require a clear strategy. Investigators must thoroughly understand the case and its timeline and progress by gathering contextual information and reviewing forensic reports. Setting specific objectives for the interview is essential: What information is known? What gaps need filling? Are there conflicts or inconsistencies to clarify? By addressing these questions, investigators can conduct focused interviews that allow them to extract the most necessary information.
Conclusion
Investigations are inherently complex, and witness accounts add another layer of intricacy. These qualitative insights can be challenging to assess but are instrumental in determining case outcomes.
Implementing rigorous investigative standards such as behavioral analysis, corroboration, and structured information gathering enables investigators to better assess witness credibility and therefore improve the accuracy of their investigative findings.
For further reading on effective interview techniques and behavioral analysis, you can refer to the FBI’s guidelines on Reading People: Behavioral Anomalies and Investigative Interviewing. For a comprehensive understanding of corroboration and other core investigative principles, refer to the Investigative Interviewing and the College of Policing's Core Investigative Doctrine.
