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Mann Et Al Detecting Lies Evaluation Essay

"What is the truth about lie detection?" This is a question that I am often asked and one that is profound because everyday we assess each other for veracity, be it at home, work, or social situations. Over the years, both in my writings and lectures, I have tried to give insight into this important question. I will try to do so again here.

As the best researchers can tell, and in my own experience as an FBI Special Agent (now retired), detecting deception is very difficult. Every study conducted since 1986, when the famed researcher Paul Ekman first wrote about this, has demonstrated that we humans are no better than chance at detecting deception (Ekman & O'Sullivan 1991, 913-920; Granhag & Strömwall, 2004, 169; Mann & Vrij 2004). That means that if you toss a coin in the air you will be as likely to detect deception as the truth. And while it is true that a very few people are better at detecting deception than others, they are barely above chance. In fact, those that are really good are only correct somewhere around 60% of the time; that means that 40% of the time they are wrong and you would not like them sitting on a jury judging you.

Unfortunately many people have come along and declared themselves deception experts over the years and that has influenced professionals and society in significant ways. I have listened to jurors post trial comment that they thought a witness was lying because they had "heard somewhere that if you touch your nose you are lying." Likewise I have talked to many a law enforcement officer who is convinced that they are experts at detecting deception. They have deluded themselves that they are, as have judges and other professionals. In fact, every time I hear Judge Judy (of TV fame) say, "I know you are lying," I cringe (unlike us she is covered by judicial privilege in saying what she wishes, the rest of us would be sued for slander). What she and others don't realize is that as Ekman, De Paulo, Frank, Mann, O'Sullivan, Vrij and others have stated, there is no single behavior indicative of deception (Ekman 1985 et.al., infra.)

So much of lie detection is based on the verbal as well as the nonverbals that one would have to have expertise in psychology, anthropology, sociology, criminology, jurisprudence, sociobiology, neurobiology, psychiatry, anatomy, physiology, communications, zoology, ethnography, primatology, linguistics, language, and grammar (to name a few), to truly understand the depth of what is behind deception and how to detect it. Fortunately there are those who have availed themselves to a wide disciplinary approach to the study of deception, but sadly few have.

Starting in 1971, when I first started studying the subject, I have heard of claims of individuals being able to detect deception based on behavior such as when someone avoided eye contact, looked up and to the right, touched their lips while speaking, cleared their throat, or displayed micro expressions. Instructors both in law enforcement and even researchers came in and lectured us young FBI agents about deception armed with videos of someone who touched their nose or covered their mouth when lying, or they showed signs of contempt as if that were scientific proof of deception. They were wrong and they were also incorrect in insisting that they were right; an anecdotal vignette of a person as they perform a behavior when lying is not science. It is interesting, but it is not science nor is it reliable. There are other times when the person uses the same behavior merely to relieve or reduce stress based on circumstances (e.g., in a police interview or the person is worried about getting to work late during a stressful traffic stop) and they are not lying but those are never shown.

As I look back on everything that has been written since the 1970s, I have begun to question some of the research. Not because the studies were not properly conducted, but rather, what did the experiments really accomplish? For over forty years, well meaning researchers have studied deception in the lab using college students. Utilizing elaborate schemes they got participants to lie about what they saw on a TV screen or they got them to take money and hide it and then lie about it and if they were successful they could keep it. Observers were then asked to determine who was lying or telling the truth and from that we get accuracy rates of from 50-60%. These experiments sounded pretty good at the time and they are still being performed. There is only one problem: a sterile laboratory environment, using college students, to me is not reality.

I say this in no way criticizing the researchers and their intentions because I think they are honestly trying to figure out how to detect deception. Some of them I know personally and admire how long they have been at this and how clever some of their experiments have been. But what I do question is the assumption that what we see in the laboratory is the same as in real life. And I have to say it is not.

Unlike what we see on television, the majority of law enforcement interviews (in fact about 97% of all police interviews) are done at night or in low light conditions outdoors, where it is noisy, there are distractions, others may be present - conditions that are not ideal as they are in a laboratory (Schafer and Navarro 2004, 3-13).

While the laboratory uses college students most of our prisons are not made up of college students. These experiments on deception, as far as I can tell, do not include individuals who are psychopaths (about 1% of Americans according to Robert Hare) or who are considered clinically antisocial (about 4-6% of Americans but about 60-70% of the prison population); nor do they use white-collar swindlers or "conmen" in these experiments who are experienced habitual liars (Hare 1993). Likewise most studies don't take into consideration that in 30-40% of arrests (with subsequent interviews), alcohol and drugs are a factor and if you ever do that kind of an interview, it is nothing like a laboratory.

Nor do laboratories test people who are stressed from travel such as at airports with canceled flights (that have serious consequences) or who may be stressed by being interviewed in a police facility: surrounded by officers with guns and handcuffs, and where their future is literally in the hands of strangers with power; not a clipboard and a white coat.

I spent a career interviewing spies and terrorists as well as criminals and I am still waiting for researchers to see how well observers perform in a laboratory on trained intelligence officers from the Russian FSB or Cuban Intelligence Service. Having done those interviews, I can say they are in no way like interviewing college students. Nor are the interviews of mobsters and "made" mafia capos the same as college students. In fact, most of the people who are interviewed in a forensic setting will not likely be in any way similar to students in a laboratory experiment. College students are not people who have to live and survive by lying such as conmen, spies, or repeat criminal offenders. These types learn to master the lie and deceit - their lives depend on it.

Likewise, no college laboratory can ever match what goes on between an intelligence officer and an interviewer conducting an interview in a hostile environment or a "denied area" of the world. Nor can it replicate the countless interviews of individuals in domestic situations where you have the wife who has been battered, tugging at you, as you interview the intoxicated husband in handcuffs, while three kids are screaming at you to let their daddy go. That lab experiment has yet to be performed and yet that is the reality of the swing shift (6 PM to 2 AM) for most enforcement officers. And not just that, most lab interviews are done while the subject is seated; conversely, at least for patrol officers, most police interviews (except the very few at the police station and on television) are actually done while standing up.

Of concern also is the profound dissonance of priorities between a law enforcement officer (who is desperate to get the facts to solve a homicide and needs information for leads or who seeks to fulfill the requirements of the statute's corpus delecti) and that of the interviewee who wants to hide what he knows because of consequences. There is a significant dynamic that takes place in the interview room between an officer and a suspect in the form of nonverbals as each feeds off of and reacts to the other. That alone effects perceptions, as does proximity to the interviewee this is very different than experiments where there is little interaction between the observer/interviewer and the interviewee. And of course, there is no social experiment that can replicate either life imprisonment or capital punishment. And so, because humans are sensitive to initial conditions as well situational context, I think it is very difficult to accept that what we see in a lab experiment with college students is congruous with what we see in real life when it comes to deception.

Recently there was talk of having machines detect deception based on cues from the face and eyes. To that I would ask, what about the rest of the body - that too transmits information? Additionally I would also ask, how have these machines been tested and vetted: in laboratories using college students? 

I have to say that over the years, there has been an over-reliance on the face for clues to deceit by some researchers at the expense of other areas of the body. In fact I argue that there has been too much emphasis on the face when years of experience doing thousands of interviews teaches us that the whole body needs to be considered to get a more accurate read on a person.

Looking for cues to deception merely from ephemeral facial micro-expressions is questionable and likely fruitless. Micro gestures may be indicative of internal emotional turmoil that is being suppressed, but that is it. The distinguished Paul Ekman, who in fact coined the term micro - expression has stated in his book Telling Lies that micro expressions are rare and they "don't occur that often" (Ekman 1985, 131, 165). Plus as others have said, there is no single behavior indicative of deception (Matsumoto et. al., 2011, 1-4). I am concerned that machines that focus solely on the face will no doubt miss other information from the body (sweating, jittery hand, etc.) or generate lots of false positives because negative emotions abound especially where such machines are intended such as airports (stress of travel, stress of being subjected to searches, or inconvenient interviews, etc) or in a police setting.

I think we need to listen to experts such as Paul Ekman, Bella DePaulo, Mark Frank, Maureen O'Sullivan, Aldert Vrij, and Judee Burgoon, who have repeatedly stated, there is no single behavior indicative of deception and that the detection of lies is very difficult (Navarro 2008, 205-208).  And this of course includes micro gestures such as a sneer or look of contempt, which is just that; contempt, not necessarily deception. That there are people who have been photographed lying while showing signs of contempt is interesting but again, that is merely anecdotal. If you interview enough people on the streets where there is a lot of police presence due to high crime rates, you will see the look of contempt quite often same as in a prison or when interacting with street gangs.

As for the polygraph, what can I say? Here is a machine that is very precise, which is why polygraphers reverently refer to it as an "instrument" and yet it does not detect deception. Wait, what? That is correct. A polygraph machine is not a lie detector and the so-called "instrument" does not and has never detected lies (Ford 1996, 221-236). It merely recognizes physiological changes in reaction to a cue (a question) but it doesn't detect lies and it can't. I repeat it can't. It is the polygrapher who interprets the instrument and your reactions to it and decides whether or not there is deception. It is this human factor, not dissimilar from some of the activity noted above, that the courts have found wanting (this is why polygraph result cannot be used against you in court) and why the American Academy of Sciences had less than choice words for the use of the polygraph in its formal report on the polygraph in 2002.

As for other gimmicks out there including machines that read eye behavior or voice stress analysis, again, I am dumbfounded by how many people are convinced that these machines actually work. Test after test has shown that these systems do not detect deception.

The Significance of This Topic:

This topic of deception would not be anything more than a curiosity if it did not have very serious consequences. Historically and even recently, people have been accosted, jailed, tortured, prosecuted, even executed when those in authority deemed them to be lying or complicit, based on their body language. Sadly, many individuals have confessed to crimes they never committed merely because someone misread them.

The price we pay for believing the unrealistic expectation that some have handed us about the reliability of detecting deception through nonverbals or other means is this: In the 261 DNA exoneration cases I have looked at, where the suspect's DNA was not at the crime scene (it was someone else who committed the crime), in all of those cases 100% of the investigators and the prosecuting attorneys could not detect the truth. They weren't just coin toss wrong (50/50), they were 100% wrong (Navarro 2011). They were so arrogantly sure that the behaviors and protestations they saw were lies that they could not recognize the truth. That is the price of falsely believing we are good at detecting deception. And if that were not bad enough, fully ¼ of these DNA exoneration cases, the individual gave a false confession. It's a funny thing about abuse and a coercive environment, in time most people, even the innocent, will yield and so they admit to crimes just to make the interview process stop (Kassin 2004, 172-193).


We all have a stake in detecting deception, after all, no one wants to invest with another Bernard Madoff or date a Ted Bundy. But we have to be realistic as to what we can detect, as Paul Ekman warned us decades ago (Ekman 1985,165-178). This goes for law enforcement officers, judicial officers, and clinicians, as well as the average person interested in the topic. It is also my hope that researchers in the future will consider who is tested, where they are tested, and how they are tested to give us a more accurate view as to who really is good at detecting deception and under what circumstances.

I have been the beneficiary of great instructors in my professional career and in my life and they have taught me how to use nonverbals to understand the thoughts, feelings, desires, and intentions of others. In forensic settings I was able to use it not so much to detect deception but rather to detect issues or concerns based on the questions that I asked. This allowed me to identify the innocent, to detect criminal activity, to uncover unknown conspirators, and to pursue leads in furtherance of investigations. But in the end, and this is cautionary, no matter what technique is used to look for deception, the only way to really know the truth is to verify and corroborate every single last detail of what someone says. And that is the truth about lie detection.

If you are interested in how body language is used in a forensic setting, please read Three Minutes to Doomsday; An FBI Agent, A Traitor, And The Worst Breech in U.S History (Scribner) - a true life account of how body language was used to catch a spy and uncover the "worst espionage breach in U.S history."

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Joe Navarro, M.A. is 25 year veteran of the FBI and is the author of What Every Body is Saying, as well as Louder Than Words. For additional information and a free bibliography please contact him through www.jnforensics.com or follow on twitter: @navarrotells or on Facebook. Copyright © 2012-2017 Joe Navarro. 


DePaulo, B.M. et. al. 2003. Cues to Deception. Psychological Bulletin, 129 (1), 74-118.

Ekman, Paul. 1985. Telling Lies: Clues to Deceit in the Marketplace, Politics, and Marriages.   New York: W.W. Norton & Co.

Ekman, Paul & M. O'Sullivan. 1991. Who can catch a liar? American Psychologist, 46 (9), 913-920.

Ford, Charles V. 1996. Lies!, Lies!, Lies!: the Psychology of Deceit. Washington, D.C.: American Psychiatric Press. Inc.

The Global Deception Research Team. 2006. A world of lies. Journal of Cross-Cultural Psychology, 37, 60-74.

Granhag, Pär Anders and Leif A. Strömwall, Eds. 2004. The Detection of Deception in Forensic Contexts. Cambridge, UK: Cambridge University Press. 

Hare, Robert D. 1993. Without Conscience: The Disturbing World of the Psychopaths Among Us. New York: Pocket Books.

Hartwig, M., Granhag, P. A., Strömwall, L. A., & Kronkvist, O. 2006. Strategic use of evidence during police interviews: When training to detect deception works. Law and Human Behavior, 30, 603-619.

Hartwig, M., Granhag, P. A., Strömwall, L. A., & Vrij, A. 2005. Deception detection via strategic disclosure of evidence. Law and Human Behavior, 29, 469-484.

Inbau, Fred E. et. al. 2001. Criminal Interrogation and Confessions, 4th. Ed. Gaithersburg, MD: Aspen Publishers, Inc.

Kassin, Saul. 2004. "True or false: 'I'd know a false confession if I saw one.'" In Granhag, P. A., & Strömwall, L. A. 2004. The detection of deception in forensic contexts. New York, NY: Cambridge University Press: 172-193).

Mann, S., Vrij, A., & Bull, R. 2004. Detecting true lies: Police officers' ability to detect suspects‟ lies. Journal of Applied Psychology, 89, 137-149.

Matsumoto, D., & Hwang, H. S., et. al., 2011. Evaluating truthfulness and Deception: New tools to aid investigators. FBI Law Enforcement Bulletin, (June): 1-9.                 

Morris, Desmond. 2002. Peoplewatching: The Desmond Morris Guide to Body Language. London: Vintage Books.

Navarro, Joe. 2003. A Four Domain Model of Detecting Deception. FBI Law Enforcement Bulletin, (June): 19-24.                 

Navarro, Joe. 2011. Clues to Deceit: A Practical List. Amazon Kindle

Navarro, Joe and John R. Schafer. 2001.Detecting Deception. FBI Law Enforcement Bulletin, (July): 9-13.

Navarro, Joe. 2009. The psychology of body language. Amazon Kindle.

Navarro, Joe. 2008. What Every Body Is Saying. New York: Harper Collins.

Schafer, John R. and Joe Navarro. 2004. Advanced Interviewing Techniques. Springfield, Il.: Charles C. Thomas Publisher.

Vrij, A. 2008. Detecting lies and deceit: Pitfalls and opportunities (2nd ed.). New York, NY: John Wiley & Sons.

Vrij, Aldert, Katherine Edward, Kim P. Roberts, and Ray Bull. 2000. Detecting Deception via Analysis of Verbal and Nonverbal Behavior. Journal of Nonverbal Behavior 24, (4), Winter 2000: 239-263.

Vrij, Aldert. 2000. Detecting Lies and deceit: the psychology of lying and the implications for professional practice. Chichester, England: John Wiley & Sons, Ltd.

Vrij, Aldert and G.R. Semin. 1996. Lie experts' beliefs about nonverbal indicators of deception. Journal of Nonverbal Behavior 20: 65-80.

Vrij, A., & Mann, S. 2001. Telling and detecting lies in a high-stake situation: The case of a convicted murderer. Applied Cognitive Psychology, 15, 187-203.

Walters, Stan B. 2003. Principles of kinesic interview and interrogation, 2PndP ed. Boca Raton, Florida: CRC Press LLC.

Warren, G., Schertler, E., & Bull, P. 2009. Detecting deception from emotional and unemotional cues. Journal of Nonverbal Behavior, 33, 59-69.

Mann et al., (2004) – ‘Detecting True Lies: Police Officers’ Ability to Detect Suspects’ Lies’




This is the second study we look at from the ‘Interviewing Suspects’ section of ‘Making a case’. As part of your OCR A2 Psychology Exam. It is further categorised into ‘Detecting Lies.

Can you tell when someone is lying?

If you answered yes, what cues to do you use to detect lies? Eye movements? Gestures?

Could you detect lies at a rate better that chance (50%)?  This would mean that you would have to be able to accurately ascertain the truthfulness of at least 6 out 10 statements.

Previous research only used students for their samples and was therefore ethnocentric and lacking in ecological validity. Mann et al,  used the first sample consisting of real Police Officers to research lie detection.

Inbau cues: gaze aversion, displaying unnatural posture changes, exhibiting self
manipulations and placing the hand over the mouth or eyes when speaking.

None of these behaviours have been found to be reliably related to lying in deception research.


To test Police Officers’ ability to distinguish truths and lies during Police interviews with suspects.

There were six hypotheses for this experiment:

  1.  “We expected truth and lie accuracy rates to be significantly above the level of chance (which is 50%), and, as a consequence of this, expected lie accuracy rates to be significantly higher than typically found in previous research (44%).”
  2. “We also expected individual differences, with some police officers being more skilled at detecting truths and lies than others. We predicted that the reported experience in interviewing suspects would be positively correlated with truth and lie accuracy.”
  3. “We expected good lie detectors to mention speech related cues significantly more often than poor lie detectors.”
  4. “We expected negative correlations between mentioning such cues and accuracy rates, in other words, the more of such cues the officers reported to look at, the lower their accuracy rates would become.”
  5. “In other words, the more of these ‘Inbau cues’ that police officers mention that they use to detect deceit, the worse at distinguishing between truths and lies we expected them to be.”
  6. ” It was predicted that poor lie detectors would be significantly more guided by invalid cues, such as ‘gaze aversion’, than good lie detectors.”

Field Experiment and correlation.


99 British Police Officers from the county of Kent.

24 were female and 75 male. Their age ranged from 22 years to 52 years.

78 participants were from CID (Criminal Investigation Department), 8 were Police Trainers, 4 were Traffic Officers, and the remaining 9 were Uniform Response Officers.

The average time served with the Police was 11.2 years and the range of time served was 1 to 30 years.


Independent Variable:

The independent variable was if the clips were of truthful or deceitful statements.

Dependent Variables:

Accuracy scores. (Either 1 = correct or 0 = false)

Self-reported behaviours, which each participant associated with deception before and after the task.

Self-reported cues used to detect deception.

Self-reported confidence scores during and after the task.

The participants were asked to judged the truthfulness of real suspects in videos of 14 real Police interviews. The Police officers all completed this task individually. Before they completed the task they filled out a questionnaire about their age, gender, length of service, division, perceived level of experience in interviewing suspects (1 = totally
inexperienced and 5 = highly experienced, the mean score was M = 3.75, SD = .85)), and the
verbal or non-verbal cues they use to decide whether another person is lying or telling the

After completing the questionnaire, the participants were given the following instructions:

“You are about to see a selection of clips of suspects who are either lying or telling the truth. The clips vary considerably in length, and the suspects may appear on several occasions. This is irrelevant. They will be either lying the whole length of the clip or truth-telling for the length of the clip. After viewing each clip I would like you to indicate whether you think the suspect is lying or telling the truth (measured with a dichotomous
scale), and how confident you are of your decision, on a seven-point scale. If you recognise any of the suspects please bring it to my attention.”

Upon completing the task, the participants answered more questions on the questionnaire. These were questions about how they had distinguished truth from lies, and questions about their confidence in their judgements.

The cameras were high enough quality to show eye blinks, but not to show subtler facial movements. In some cases the suspects legs could not been seen, thus leg movements were not analysed. The audio was of good quality.

Videos were only shown if the truthfulness of each word was known to the researchers.

The length of each video clip varied from 6 to 145 seconds: in total there were 54 clips, 23 truthful and 31 deceptive. The number of clips for each suspect varied between a minimum of 2 to a maximum of 8. This ensured that each participant viewed at least one truth and one lie. The clips were presented in a random order to ensure the same suspect was not viewed consecutively.

Permission to approach and use Police Officers was granted by the Chief Constable. The Police Officers were told that they would be participating in a study ‘about Police officers’ ability to detect deception,’ there were also informed that their participation would be anonymous.



The difference between the mean lie accuracy and truth accuracy was not significant: 66.2% and 63.6% respectively. However, these results were significantly above chance, which was 50%.

For the 99 participants, in total, 677 behaviours mentioned on the
questionnaires before and after completing the task were coded.

Participants mentioned a mean of 6.84 behaviours.

The most frequently mentioned cues to detect lying were gaze, movement, vagueness, contradictions and fidgeting.

Participants were significantly more confident after they had viewed truthful clip, than after they had viewed a deceitful clip. Those two confidence measures were significantly correlated with each other.

Experience in interviewing was weakly positively correlated with truth accuracy and lie accuracy.

Neither the truth accuracy – truth confidence correlation, nor the lie accuracy – lie
confidence correlation were significant.  Neither was the post-task estimated
accuracy significantly correlated with the actual lie accuracy or actual truth accuracy.

Age, length of service and experience in interviewing suspects were not significantly correlated with truth confidence, lie confidence or post-task estimated accuracy.


The levels of accuracy found in this study exceed those found in other studies and are the highest for a group of ordinary Police officers. The more experience a Police officer has the better they are at distinguishing truths from lies.

Higher accuracy is found in people who do not use stereotypical Inbau cues when detecting lies, instead rely more on story cues, for example contradictions.

Mann et al., Evaluation

– No Control group – therefore comparisons cannot be made between Police officers and lay people, to understand if there is something fundamentally different about Police officers that makes them better at detecting lies than lay people.

+ Ethics – the reason there was no control group is because ordinary people could not be allowed access to real case materials.

+ High Standardisation, the experiment is highly standardised, each participant was subject to the same videos and suspects.

+ Ecological Validity, as experiment one used real police officer, we can say that the experiment is high in ecological validity. However, we can also argue the opposite as the participants only watched videos of suspects.

+ Ethics, as the participants were informed about the interview beforehand, we can say that the study was ethical.

– Ethnocentrism, the study was only focused on British police officers, and therefore cannot be generalised to other populations.

+ Experimenter bias, as the results of both experiments were analysed by laboratory assistants who were blind to the conditions, we can say that the study is lacking in experimenter bias, which is a strength.

+ Construct Validity, the results of the study showed support for the effectiveness of the cognitive interview.


Audio Podcast

  1. Mann et al., (2004) – ‘Detecting True Lies: Police Officers’ Ability to Detect Suspects’ Lies’
Further Reading

OCR A2 Psychology Student Unit Guide: Unit G543: Forensic Psychology (Student Unit Guides)


Article Name

Mann et al (2004)


Mann et al., (2004) - 'Detecting True Lies: Police Officers' Ability to Detect Suspects' Lies' Can you tell when someone is lying?


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