How to Tell If Someone Is Lying: Expert John Douglas’s Tips

John E. Douglas grew up in Brooklyn, New York, and initially thought he would become a veterinarian. He ended up taking a far different path, carving out a career in the FBI’s Behavioral Science Unit. During his tenure there, he revolutionized how the entire agency profiled criminals, allowing them to catch some of the most dangerous killers in recent history.

Throughout his time at the FBI, he interviewed infamous criminals, like Charles Manson, Ted Bundy, and John Wayne Gacy, Jr., to better understand the psychological profile of the average serial killer. His memoir, Mindhunter: Inside the FBI’s Elite Serial Crime Unit, chronicles his time as a criminal profiler and investigator and served as the inspiration for a television drama of the same name.

Learning how to spot a lie can help you in immeasurable ways. Former FBI criminal profiler John Douglas has made a career out of trying to understand deceptive behaviors. These tips from him can help you become a human lie detector:

• Consider the level of empathy. Think about the person you’re talking to and ask whether or not they seem capable of empathy. “That’s the lesson I took away from . . . John Wayne Gacy, the total lack of empathy,” John recalls, “Pathological liars possess those same traits and can, therefore, be very convincing.” When someone lacks an ability to relate to the happiness and pain of others, it’s a telltale sign lying might come easy to them.
• Destabilize the liar. Pay attention to how the potential liar reacts when you throw them a curveball during your conversation. “Ask unexpected questions to catch someone off guard,” John suggests. For example, change the subject to make small talk about something like the weather or a recent sports game. By doing so, you reduce the prevalence of lying in your conversation, making it easier for you to notice any differences in how the subject talks about the truth versus any potential lies.
• Establish a baseline. To notice signs of deception, you need to know what a person acts like when they’re at ease and telling the truth. “Watch for changes in behavior,” John says. When you have more of a baseline understanding of a person’s natural behavior, it becomes easier to single out erratic or off-kilter mannerisms indicative of deception.
• Learn as much as you can. To detect all potential signs of lying, learn as much as you can about the person you’re talking to ahead of time. John believes the reason he’s had such success rooting out lies from criminal interviews is because “before [he does] any kind of interview like that, [he is] armed with information.” In such a high-stakes environment, knowledge is power.
• Monitor combativeness. If someone becomes hostile during the course of an ordinary conversation, it could be a red flag they’re lying to you. “[Liars] can also have a tendency where they wanna fight,” John says. “So they're taking on this extremely stiff personality—really, really stiff where they're not moving at all.” Sudden combativeness like this can be a dead giveaway the person is trying to hide some aspect of the truth from you.
• Never trust a polygraph test. Within the law enforcement community, polygraph tests are subject to a great deal of controversy. “The theory behind a polygraph is when people are lying, they experience a different emotional state than when they are telling the truth,” John says. “Their heart rate increases, they sweat more, or their breathing changes. These are all physical signs of anxiety that are difficult for the body to hide. But some people can [hide them].” This applies to both the criminal psychopaths John interviewed as well as less egregious pathological liars.
• See what liars hide in plain sight. Pay attention to how the person might hide their lies behind their public persona. “John [Wayne Gacy] told us in his interviews that being a clown was the perfect disguise,” John Douglas remembers. “He said, ‘Being a clown, someone who performs for parents and children in the community, people just trust you.’ It was one of the deceptions Gacy used to hide his monstrous activities in plain sight.”
• Watch body language. You don’t have to be a body language expert to notice a liar acting in an erratic manner. “Avoiding eye contact, repeating a question when you ask them a question, they repeat the question because they're looking for time,” John says. “They need time to come up with a deceptive answer to you. They may be fidgeting. Their posture, it may be in this fight-or-flight syndrome.”

Detecting lies can be difficult, but it is possible. Here are a few techniques you can use to ferret out indicators of deception:

• Notice atypical vocabulary. Pay attention to whether the person starts using third-person pronouns instead of first-person ones throughout your conversation. This verbal cue might indicate they’re trying to distance themselves from the action of the story and deceive you.
• See if they buy themselves time. Some people lie without any anxiety, but many others find untruthfulness nerve-wracking. You might notice this latter group trying to change the subject, stuttering, and otherwise buying themselves time after you ask them a pointed question. Keep track of facial microexpressions and other fidgety body language to further shore up your case that they might be lying.
• Think about their past track record. Ask whether the person has a history of telling white lies or fibs. This might not correlate to them lying to you in the present moment, but it suggests they have no problem playing fast and loose with the truth when necessary. In the same way, if someone has a long track record as a truth teller, it’s less likely they’re lying to you but still not impossible.

Getting to the core of human behavior takes knowledge and skills—just ask former FBI criminal profiler John Douglas. Learn how to spot a liar and uncover John’s tips for identifying other deceptive behaviors when you sign up for the MasterClass Annual Membership.