Chemicals called catecholamines are released in the body when someone lies, causing the person's facial area to itch. He will unconsciously scratch his chin, or more commonly, the side of his face. Moreover, the nose is also sensitive to the release of chemicals when telling a lie, and there will be a slight, imperceptible swelling of it accompanied by an itchy feeling. When a person touches his nose, scratches it, or rubs his finger vigorously beneath it during the interview, he's signaling a lack of candor. Similarly, if he rubs his eye, it's a potential signal that he's not being truthful.
It's been said that the eyes are a window to the soul. In police work, they can help us determine deception. People normally maintain eye contact during a conversation about sixty percent of the time. Some will avert their eyes every time they lie. The usual blinking rate is about five to six times per minute, or every ten to twelve seconds. When someone blinks more rapidly, or gives several blinks in quick succession, it's a good indicator that they're not telling the truth. Another signal of deceit is when an interviewee closes his eyes for several seconds before, during, or after answering a question. Their eyelids may even flutter during this closure.
Postures that indicate a person doesn't want to answer questions include leaning away from you, stiffness of the body, crossing the arms on the chest, turning sideways to you, wrapping an ankle around a chair leg, or extending a foot forward as they slouch in a chair and turning that foot on its side. Bouncing or swinging of the foot of a crossed leg indicates nervousness and possible lack of candor. If a suspect turns his body with his feet pointing toward an exit, he's sending a subconscious signal that he wants to get away from the current situation.
I asked Mark his opinion about some of the sociopaths we encounter on the street; you know, the ones who lie more often than tell the truth. Might the same indicators be present in these individuals? He told me a person's psychological makeup can be important in both the signals he gives and the answers he provides. People who are sociopaths are less likely to be as stressed while lying as the normal individual. They won't have the increased heart rate, higher blood pressure, rapid respiration rate, and increased rate of perspiration that people ordinarily exhibit when they're under the stress of lying to a police officer. Also, people who have narcissistic or dissociative personality disorders will react differently when lying.
Being able to identify lying and deception is not only important on the job, it can also come in handy when we're off-duty. Think about dealing with sales people, repairmen, neighbors, even our own family members. Psychological tests indicate that about ninety-one percent of people admit to lying on an almost daily basis. College students lie to their parents in about every other conversation. Children will first conjure up a successful lie at about age five. It's part of growing up and establishing a separate and distinct personality. Until then, they'll exhibit many signs associated with lying such as holding their hands behinds their backs, shuffling side-to-side, looking away, hesitating before answering, stammering, using "ers" and "uhs" more than usual, and touching their mouth or nose.
Mark's thirty years investigative experience helped him catalog a variety of body movements, facial expressions, and verbal responses, allowing him to determine quickly which line of questioning to pursue. His book is a valuable resource for any LEO who wants to tweak his BS antenna; it helped me.
However, a word to the wise: don't leave the book laying around the house. Your spouse may read it. Enough said.
Stay safe, Brothers and Sisters!