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How to Tell Whether Someone is Lying in an Investigation Interview

Take your training with a grain of salt. Even the most skilled investigator can be fooled.

Posted by Timothy Dimoff on February 18th, 2020

As an investigator it is your job to ask the right questions, assess the answers and draw conclusions. But can you tell if someone is lying in the investigation interview? You have been trained in this and you probably feel confident in your ability to detect deception. However, even the most skilled investigators can be fooled.

Non-Verbal Indicators of Lying

Traditionally, body language is often used indicators of lying, however due to everyone’s responses varying, this may not always be a clear indicator. For example, one person’s ability to lie may be better than another’s, or they may have more time to prepare their answers.

Download the eBook: How to Detect Deception in Investigation Interviews.

While non-verbal behavior can be a good indicator of whether someone is telling the truth, there are other factors that enter into the equation. These factors can include differences in behavior due to cultural differences. For example, someone may be shaking their head from side to side in agreement — which is common in India, but in North America it signals non-agreement.

All facial expressions, tone, posture and other common non-verbal signals should be taken into account, but not relied on solely as a complete assessment of lying in an investigation interview. Remember, every person differs in their behavior and not everyone exhibits nervousness or lying in the same way.

Avoid Aggressive Questioning

Another factor that must be considered when determining if someone is lying is the form of questioning used. The manner in which someone is questioned can have an effect on the way they answer questions.

Many of the best interviewers use the PEACE model of Investigation Interviews. Download our free PEACE Model Cheat Sheet.

If they feel threatened, they may exhibit signs of stress or fidgeting, which can make it look like they are lying, but this doesn’t mean they are actually lying. They may be just anxious due to the manner of questioning. If the questioning is too aggressive, it can bring out speech errors, gaze aversion and other stereotypical behaviors usually associated with lying.

Concealment or Falsification?

When interviewing, keep in mind that most people who lie do so using either concealment or falsification. If the subject is not being forthcoming, leaving out information or otherwise evading the question, they are most likely concealing some truths. If they are intentionally misleading you, they are most likely doing so with the intent to lie.

As an investigator, it is your job to determine if a subject is lying in an investigation interview. While it can be confusing, there are some good indicators to help you. Next month I will delve deeper into these methods such as falsification and concealment, and the strengths and pitfalls of body language to help you uncover the truth.


Timothy Dimoff
Timothy Dimoff

President, SACS Consulting & Investigative Services

Timothy A. Dimoff, CPP, president of SACS Consulting & Investigative Services, Inc., is a speaker, trainer and author and a leading authority in high-risk workplace and human resource security and crime issues.
He is a Certified Protection Professional; a certified legal expert in corporate security procedures and training; a member of the Ohio and International Narcotic Associations; the Ohio and National Societies for Human Resource Managers; and the American Society for Industrial Security. He holds a B.S. in Sociology, with an emphasis in criminology, from Dennison University.

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