Demeanor evidence is simply reading people’s external demeanor, such as body language or speech, to try to read between the lines and determine a person’s truthfulness or lack thereof. After police officers have been on the job for several years, they grow more confident in their ability to spot lies. I have heard this described as developing a fine-tuned “BS detector.” As such, officers tend to grow in confidence in their skill at detecting deception and lies as their experience increases. No doubt, this skill influences officers’ investigatory decisions. If an officer is accurate at detecting lies and deception, this is obviously helpful in police work.

Notably, research indicates that law enforcement officers fare no better than the general public at detecting lies and deception.

Leakage hypothesis theory

Much of the lie detection and demeanor evidence is based on the leakage hypothesis theory. This states that people are not able to hide their lies and deceptions, and these lies and deceptions will leak out of their body language. As a result, police officers are familiar with this theory and attempt to pick up on these leaks to help them with their investigations.

Problematic training of the past

Over the years, I, like other police officers, have attended training on interview and interrogation techniques. Most of these classes have been really beneficial; it is important that officers are trained to interview people effectively. 

However, not all classes are created equal, and some are not so great. For example, early in my career, I remember taking a class that seemed to instill overconfidence in officers’ ability to detect lies and deception. In truth, several of the interview and interrogation techniques taught in the past were simply not valid or based on research. I specifically remember a technique that became popular. The idea was to watch people’s eyes as they answered questions. If the person’s eyes went up to the right, then they were likely being truthful because they were accessing the “memory” part of the brain. However, if their eyes went up to the left, they were accessing the “creative” part of their brain and, thus, were likely lying. To be clear, while it is an interesting technique, there is no research that backs it up as a valid technique. In fact, if an officer had confidence in this technique, it could ultimately lead to wrongful convictions.

What about the eyes?

Many people widely believe that if someone avoids eye contact, they may be perceived as deceptive or hiding something. Moreover, consider if an officer believes a suspect is lying because they won’t look them in the eyes. The officer should know that avoiding eye contact could be due to a variety of reasons, including psychological factors like anxiety, social anxiety, low self-esteem and neurodevelopmental disorders such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). In addition, cultural norms also play a role, as in some cultures, direct eye contact is considered rude. I am trying to make the point that we should not put too much confidence
in our ability to detect deception through eye contact.

Warning: You might not be that great at detecting lies and deception

All officers should be aware of important research conducted by Pär Anders Granhag, a professor of psychology at the University of Gothenburg. His research focuses on deception detection, eyewitness testimony and interrogation techniques. According to Granhag’s research, microexpressions, fleeting facial movements lasting mere fractions of a second, have garnered scientific attention. However, a significant problem with microexpressions is that liars and truth-tellers both show microexpressions. 

Moreover, there are no microexpressions that liars show that truth-tellers don’t also show. What is more troubling is, when relying on these nonverbal indicators, the accuracy rate barely surpasses random chance, reaching only 54% compared to the baseline of 50%. 

Notably, research indicates that law enforcement officers fare no better than the general public at detecting lies and deception. The sole distinction observed between police and other study participants is the officers’ heightened confidence in their assessments. This combination of low accuracy and high confidence presents a concerning situation, which could lead to wrongful convictions. In addition, reliance on fidgeting, gaze patterns or signs of nervousness as deception indicators lacks all empirical research support.

Recording interactions

Unintentional miscommunication between police and suspects will happen from time to time. However, miscommunication between police and suspects may have a substantial impact on the evidence presented in a criminal prosecution. As such, many court requirements, laws and policies now require recording police interrogations and even routine public interactions. Recordings are important to corroborate or disprove demeanor evidence claims. 

Miscommunications

Recordings can help clear up confusion that can take place during human interactions. For example, I recently watched a quick video where an officer made a traffic stop in very hot weather. The officer asked the driver how much he had to drink that day. The driver thoughtfully answered he had been “drinking but had not drunk enough.” The officer followed up his response by asking him if he would perform field sobriety tests. The very confused driver answered “No.” At this point, the driver was immediately placed under arrest for driving while impaired. The whole interaction lasted less than a minute. However, the whole incident ended up being a miscommunication. The driver thought the officer was talking to him about drinking water to stay hydrated because it was really hot outside. The officer thought “drinking” meant alcoholic beverages and that he had just gotten a confession. When the officer told the driver’s passenger the driver was being arrested for driving under the influence, the passenger convincingly responded that her husband never drinks alcohol! At this point, it seems the officer began to realize that a miscommunication had taken place. However, the recording was important in this interaction to show what happened.

Reading body language is helpful, too

When I worked in law enforcement, I was in a town that had a university. So, every year, new first-year students would come to the university. As always, it was interesting as a police officer to be able to tell who was legal to drink alcohol and who wasn’t when they were walking home at night. Often, there was an indicator that if somebody was under the legal age and they had been consuming alcohol, they’d be walking extremely carefree, laughing and joking with their friends at night. Then, they would look over and see the police car, and suddenly, their body language would shift dramatically. They would straighten up, stiff as could be, and walk like they’re a robot walking straight down the sidewalk, looking ahead and not talking. You could tell from their body language that they had done something wrong. It’s usually a pretty good sign that they were consuming alcohol and were under 21 years old. However, if somebody was over 21 years old and wasn’t violating the law, their reaction when they saw us would not change at all.

There is a place for reading body language. We, as people, read body language all the time. We can become pretty good at reading between the lines of what people may be thinking or hiding. Yet, this is something that we’re not as good at as we think we are, so we must not be overconfident about this skill because it could lead to our investigations going astray.

Conclusion

I’ve made the case in this article that sometimes we think we’re better than we really are at detecting lies and deception. As such, it’s important that we take what we believe to be misdirection, lies and deception with a grain of salt. Importantly, we must do a thorough investigation to make sure we are heading in the right direction in our investigations. However, I’m also not trying to say that we are completely inept as human beings at detecting lies and deception. Reading body language to detect lies can be helpful. We just have to be very careful in how we utilize this skill. So, as a whole, we need to continue to develop this skill and learn about it but also know that the research indicates that we are not as good as we think. In sum, we do not want to have overconfidence in thinking that someone’s lying when, in fact, they may not be. 

Dr. Matthew Loeslie is an assistant professor at Minnesota State University, Mankato. He has held leadership roles such as academic dean, criminal justice program director and lecturer. In addition to his academic experience, Dr. Loeslie has also served as a police officer and trainer. He holds a Doctor of Criminal Justice from Pennsylvania Western University, California, and a Master of Arts in Criminal Justice Leadership from Concordia University–St. Paul. He can be reached at linkedin.com/in/matthewloeslie.

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References

Brennen, T., & Magnussen, S. Research on non-verbal signs of lies and deceit: A blind alley. Frontiers in Psychology, 11. https://doi.org/10.3389/fpsyg.2020.613410. 2020.

Cincinnati Law. (2018, November 19). Lie Detection and Demeanor Evidence, Dr. Par Anders Granhag [Video]. YouTube.

Von Hippel, W., & Trivers, R. (2011). The evolution and psychology of self-deception. Behavioral and Brain Sciences, 34(1), 1–16. https://doi.org/10.1017/s0140525x10001354.