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Determining Whether Someone is Lying in an Investigation Interview – Part 2

Determining if Someone is Lying During an Investigation Interview

By Timothy Dimoff

Look for “tells” but keep an open mind.

Last month I wrote about some basic traits that could come into play to determine if someone is lying in an investigative interview. This month, I will go into a little more detail.

Sorting fact from fiction is not always as easy as one would think. Investigators often think they can spot a lie or that they can easily sort out the truth, but it can actually be much more difficult than one may think. A good liar can fool even the best of us, but there are some steps a good investigator can take to help determine a lie from the truth.

Get to the truth without badgering your interview subject. Download the cheat sheet:The PEACE Model of Investigation Interviews.

Get a Baseline

Determining whether someone is lying begins with a good baseline assessment. This assessment should include asking open-ended questions while studying the behavior of the interviewee to determine any indicators of emotion, control and cognition.

Once you are comfortable you have achieved a solid baseline assessment, then you can switch to closed-ended questions in order to determine specific responses. Keep in mind that differences in speech, behaviors, cultural differences and other personality traits may influence their responses and body language making it more challenging to determine a liar from a truth teller.

What are the "Tells"?

However, there are some general “tells” that people may exhibit when lying in an investigation interview that can help you making your determination including:

  • Check their eyes. Generally, someone who is lying will have a difficult time looking you directly in the eye. If you spot them looking at the floor instead of looking you in the eye, it may be an indicator that they are lying.
  • Another “tell” is shifting of the eyes. Someone who is being truthful generally will not have any issue looking you directly in the eye.
  • Look for changes in their speech. A drop in their tone or if the slow or speed up their speech, it can indicate that they may be lying. Check for sudden pauses or lots of throat clearing as well.
  • Another “tell” is offering way too much information. If they stammer or are speaking in the third person, beware also. While these are not absolute, they can be indicators of lying.
  • Body language can also be an indicator. There is a lot out there on body language, pro and con, but understanding it can be helpful to an investigator. Keeping in mind any cultural or unique personality traits, there are some general body language “tells” that can help you determine a liar. These include:
    • fidgeting too much or even too little
    • sudden changes in body posture
    • shuffling their feet, or even trying to cover up their body - usually the mouth, throat, chest or even their abdomen
    • lip biting, nail picking or nail biting
  • Sudden changes of expression can also be a “tell”. Switching from calm to anger, anger to disgust, sadness to fear or any other quick changes in display of emotion can also be a red flag.

Keep an Open Mind

While all of these “tells” will help to give you an idea of whether someone is lying in an investigation interview, they are not absolutes. A good investigator will take everything into account and keep an open mind. There may be extenuating circumstances that come into play in the interviewing process.


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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