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  • Writer's pictureBobbi K Dominick

How Can You Tell When Someone is Lying?

I found an image on Pixabay of this torture chair when I searched for images related to "credibility" and it reminded me of a question I get asked at cocktail parties when I tell people I am an investigator: "How do you know when someone is lying?" Well, I don't put them in this medieval torture chair until I am convinced they are telling the truth.

Instead, we investigators have a number of cues and tips that we look for when trying to determine who is telling the truth. Here are a few:


If you are a fan of NCIS, as I am, you know of the famous "Gibbs Gut." Gibbs will listen to a witness tell his or her story, and then pronounce them truthful or lying. And he is almost always right (the exception being Rule #51 "Sometimes you are wrong"--if you are an NCIS fan you are also very familiar with "The Rules").

Some may advise you to rely on your instincts, such as looking at body language, demeanor, how the person uses their eyes, shifting their positions, stammering speech, and similar cues. Popular mythology has even gone so far as to proclaim some of these as instant "human lie detectors." But research shows us that these "cues" are right only about 55% of the time. Many witnesses, when giving their story, are nervous, forgetful, fidgety, etc. but it does not necessarily mean they are untruthful. Instead, it is better to listen carefully to the story, the facts that the witness is providing. A relaxed conversational style of questioning can yield more useful information than a cross-examination (or a torture chair).


Often I just want to hear people tell their story, from beginning to end. Using open ended questions can accomplish this "Tell me what happened?" "What happened after that?" When the story is over, I can go back and ask lots of detailed questions about who, what, where, why, etc. Often, (but not always) if a person is untruthful, the details may change as the story is retold. I might ask the witness to recount specific details, who was there, where were they standing, what words were said, etc.


Often a witness will tell a story. I will then request contemporaneous emails, memos, documents from the organization to track details of the story. I don't know how many times I have interviewed a witness that "feels" believable, and tells a great story, only to discover contemporaneous documents that tell a different story. And sometimes, the documents were created by the witness themselves!


Often, the same event was witnessed by more than one person. Perspectives are different for each person, but if three people are telling one version, and the other witness is telling a different story that supports their complaint, their credibility may be reduced. At the same time, be careful if the issue involves trauma. Recently, we were engaged in a national debate over the credibility of a report of sexual assault (you know the one I mean). I saw so many people say "Why can she remember this but cannot remember whose house she was at." Trauma can do that, so a failure to remember some details does not mean the person is untruthful. A person who experiences trauma may remember details that others don't remember, or not remember unimportant details, because of the trauma that person associates with the event. I seek out information on trauma and how it impacts recollection to make sure I am considering that factor in assessing credibility.


I look for any way possible to confirm facts disclosed by the witness. This might mean searching out publicly available information, like public records or social media. For example, one witness's story was of overwork and a constant struggle to keep up with work during the work day. Publicly available social media sites revealed that the person was spending excessive amounts of time during work days on social media activities that had nothing to do with work.


There are several ways that those who judge cases use to assess credibility (judges, juries, agencies, etc.) I keep a list of all of those factors, and when I have conflicting stories from witnesses, I pull the factors up and assess the credibility using those factors. Some of these include:

1. Inherent Plausibility. This factor requires me to just the reasonableness of the witness's testimony against all of the evidence I have gathered. Did it happen the way the witness says it happened?

2. Motive to Falsify. This factor assesses whether the witness might be stretching to truth to match a narrative they have told, to recover financial gain, to get themselves out of trouble, etc. On the other hand, a witness who has no interest in the outcome of the matter, who has nothing to gain or lose, might be given more weight for that reason.

3. Corroboration. This is one of my key factors. How much of this witness's testimony was corroborated by other facts? Did s/he tell me the same story told to others? Did others agree with his/her version of events? (the search for documents noted above is a search for corroboration).

4. Inconsistent statements. Lawyers call this "impeachment." Did the witness testify consistently with prior statements he or she made on the subject? Or did the story changed. And, as noted in the "narrative" comment above, sometimes the story changes from one telling to the next even within the same interview.

Nothing substitutes for good old fashioned digging, and an honest neutral assessment of the information gathered. Not even the torture chair.

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