Can I Tell A Person Is Lying By Watching Their Body Language?
One of the most exciting investigative activities is conducting interviews and interrogations. We love talking with people and learning how to get the most information possible from our time with them, especially if they are deceptive.
Detecting deception from an individual seems to be a cat-and-mouse chase that most people enjoy. Maybe this feeds some ancient instinct we have to control our environment and have the skills to glean information that less skilled people cannot. I remember starting as an investigator and hearing my mentors talk about the interviews they conducted, often stating, "That guy is lying to me."
Many people are aware that most communication occurs on a non-verbal level. Most messages people relay come from verbiage, tone, and body language. Techniques that purport to teach investigators how to detect deception focus on body language.
Detecting deception by observing body language requires us to accept some underlying assumptions.
- Body language is a large part of human communication.
- A person is largely unaware and not always in conscious control of their body language.
- When a person is under stress or being deceptive, they will produce particular body language cues, gestures, or behavior that differ from their normal baseline.
- An investigator can be trained to "read" another person's body language and use it to obtain more information about what the subject is saying or not saying.
These assumptions must be true for an investigator to develop the ability to "read" a person. But are these assumptions more fact or fiction?
Many investigative courses teach people different aspects of detecting deception. Are the person's arms or legs crossed? What are they doing, and where are they looking while answering your questions?
These gestures, we were taught, all mean something. Perhaps a particular question made them tighten up or feel like they needed to be more guarded. Maybe covering their mouth with their hand when speaking is a subconscious action that physically attempts to hide a verbal lie. And those eyes? The person recalls an event when they look in one direction, but they are manufacturing an answer if they look to the other side. Over the years, I've heard all this and more from several instructors at training courses.
Many investigators attend these courses each year, paying their fees, hoping to learn how to detect deception. So that during an interview or interrogation, they will know if someone is trying to hide something.
I believe investigators should get all the training they need or can afford. It is nice to develop tools for the proverbial "toolbox" that you can reach into one day should a task require that specific tool. For this reason, I would never discourage an investigator from getting all the training they can. Still, as professionals, we need to understand which tools are legitimate and which are exaggerated or gimmicks.
Many investigators attend these courses to learn how to detect deception. But what will they do with that information, and more importantly, how is it related to their case? While detecting deception might help point the investigator in the right direction, deception-detecting techniques will never be objective enough to add to a report, be submitted in court, or become the deciding factor in a criminal conviction. And because they lack these abilities, their use is far more limited than most investigators admit.
Here are ten things professionals keep in mind when trying to detect deception by watching someone's body language:
1. The ability to read a person's body language feeds a human need to know what others want to hide. It is peculiar that we don't worry about others gaining important information from our body language, while at the same time, we believe others fall prey to this phenomenon. It is also odd that body movements designed to facilitate communication, which likely developed before language, can communicate a message the person is trying to conceal. The science here is thin.
2. The Polygraph Problem. A polygraph is a machine that claims to have the ability to detect deception in a person's responses to questions. It creates a baseline and identifies changes in a person's heart rate, breathing rate, blood pressure, and perspiration level. We assume these are variables a person cannot control, and deception will cause stress that will trigger spikes in these bodily functions. The polygraph problem is an investigator's belief that they can gauge subjective body movements and gestures as accurately as a polygraph machine can read a person's pulse, blood pressure, etc. The fact is that a polygraph can detect minute changes that a human being is unable to do. Still, polygraph results are not admissible as evidence, so how can an investigator's idea about why someone crossed their arms over their chest be more objective than measuring someone's heart rate? It can't. The lesson here is that detecting a change in the body only teaches you how to see a difference in the body. It tells you nothing about what is happening inside a person's mind.
3. Establishing a baseline can be a helpful tool. I believe it is true that establishing a baseline can be a valuable tool in detecting changes in a person's behavior. Polygraphers do this by asking basic questions that everyone knows to be true or false before going into the questions about a case. Investigators conducting interviews can observe a person's demeanor during the introduction or ask non-threatening questions about the person, such as their name, address, employer, etc. Once again, however, while a baseline can help you detect deviations from a person's normal behavior, it won't tell you why that deviation occurred. It is a jump in logic to assume that a question that makes a person suddenly nervous, such as asking about where someone was the night a crime occurred, means the person is hiding details about the crime in question. Maybe they were having an affair or working a secret job they did not want to be made public. Even if indicative of stress or deception, changes in behavior do not mean the person is lying about the matter you are investigating.
4. A person's body language will not solidify your case. Building a solid case will require evidence. Investigators go through a stringent process of gathering information and maintaining its integrity so that the evidence is not tainted. The key here is to collect objective data and handle it so that nobody will question its integrity. Body language cues or changes in behavior will not meet these criteria and are not evidence. The fact that a person yawned or started to sweat will not make weak evidence strong or strong evidence weak. It can add to the totality of the circumstances, but it will not solidify your case.
5. Claims of deception based on body language are not admissible in court. Not to beat a dead horse, but what good is any aspect of an investigation if it cannot be produced in a criminal or civil hearing? Information that is not admissible is irrelevant, no matter how strongly we feel about it. If the only evidence that someone stole money from the cash register is that they became nervous when you asked them about money problems or suddenly shifted away from you when you asked the question, you have a problem. Any decent defense attorney would rip these assertions to shreds, and rightly so. They are simply not evidence of the crime. They are only subjective interpretations of what you believe, even if it is a part of your training and experience.
6. An interview is a small part of an investigation. We are speaking about detecting deception during an interview, but we should remember that the interview is just a small part of the investigation. Depending on the nature of the alleged violation, there should be other evidence to gather. Maybe this includes witness interviews, but it should also include documentation, photographs, emails, contacts, video, DNA, fingerprints...you know, tangible evidence. Gone are the days when an interview or witness statement, on its own, could provide a successful prosecution. Even cases containing abundant circumstantial evidence can be hard to win. Like a suspect's testimony that "I didn't do it" won't defeat an abundance of material evidence that shows otherwise, we shouldn't expect an investigator's assertion that "He did it" to stand without additional evidence. The interview is too small to be considered the brunt of the investigation. The importance of body language diminishes when we view the totality of an investigation.
7. If you have nothing else, then you have nothing. If the only thing pushing your case forward for prosecutorial consideration is based on body language, and you have no other evidence, then you have no case. Confessions can be the icing on the cake. They corroborate other evidence or point to information the investigator might not have known. If the subject of your investigation has not confessed, but you are disputing what they said based on how you read their body language, you will need other evidence to make your case. If you have nothing else, then you have nothing. The key here is to focus on gathering hard evidence. This evidence will make it much easier to corner your suspect if they tell lies during their interview.
8. Remember that technology is constantly changing. Some technology improves what came before it, but other advances in research often prove former theories to be false. For example, I remember attending a body language class that focused on watching the suspect's eyes right before they answered your question. A theory backed by the era's technology "helped" investigators determine whether the interviewee recalled factual information or manufactured false information. Some schools even taught that the investigator could tell whether the person was processing their story through an internal visual or auditory lens while they were thinking. This technique was introduced and used by investigators for many years until technology showed us this theory was utterly baseless. Don't place your case in the hands of subjective ideas; focus on gathering objective evidence to prove your case.
9. It is difficult to determine the value of witness testimony. There was a time when witness testimony held more weight, judges considered the testimony of a law enforcement officer the truth, and if a witness said they saw the suspect commit the crime, it was good enough for a criminal conviction. Those days are long gone. In the modern investigative era, it is hard to evaluate the usefulness of the information provided by a witness. It is feasible to have one witness saying a suspect committed a crime while the suspect says they did not. This situation turns into the classic he-said-she-said model that pits one person's statements against another. The witness statement will likely fall short if no other corroborating evidence exists. After all, we have all seen cases where a person witnessed the suspect commit the crime in question. But, we have also seen instances where the reporting person makes false allegations against a subject for myriad reasons. One person's account of what happened will likely not be enough to sustain a case without additional supporting and corroborating evidence. So without further evidence, the weight of one person's statement is hard to ascertain.
10. An investigator's assessment of another person's body language can be incredibly subjective. There is just not enough to say here. One of the problems top researchers of the human mind face is that studying the mind relies on a person's subjective experience of what the person is experiencing. While the investigator is not trying to solve the mind-body problem, we have to admit our ideas about the meaning of another person's actions are almost entirely subjective. Investigators must always consider subjectivity and bias as natural qualities of the human mind during their investigation. Concepts like "experience" or "expertise" are quick recipes for fooling ourselves into believing we have a grasp on objectivity. The lesson here is that one human's ideas about what another human being is experiencing are currently unknowable by the world's best scientists. So, yeah, they are also unknowable by the best investigators.
The key is for professional investigators to learn not to rely on unreliable things. We must keep the interview and interrogation process in perspective of what they mean to our case. A case disposition will likely not be affected by our subjective ideas, like whether a witness or suspect is being deceptive.
Professionals live by big boy and big girl rules. We must admit that knowing when another person is deceptive is not the goal of the investigation. The purpose of the investigation is to prove what happened objectively. We always aim for objective evidence and there is nothing objective about reading body language.