Since the beginning of time, Man has searched for techniques to detect deception in others. At times the infliction of pain or torture was considered a useful method. This was, eventually, considered a flawed path as the target of “interrogation” may say whatever the interrogator wants to hear to end the pain. Mechanical methods such as polygraph and Voice Stress Analysis have been experimented with and refined to attempt to detect deception. Mechanical methods require the consent and cooperation of the individual to achieve any level of success. A subtle technique was needed to attempt to detect deception without the consent of the target individual through coercion. This technique is the use of physical mannerisms or “body language” to try and detect deception. These mannerisms are non-verbal communication.
Using body language, subtle changes in body movements or posture to detect deception is a common technique used by detectives, uniformed police officers and anyone charged with investigating violations of criminal or civil law, espionage or any other situation in which someone might have a reason to conceal the truth. Body language is generally considered the body’s unconscious responses to stimulus. The body can respond unconsciously to both positive and negative stimulus. Assessing body language is somewhat complicated as it requires the interviewer to multi-task between holding a conversation and observing physical reactions by the other person. When attempting to judge a person’s honesty during a conversation it is best to, first engage in non-confrontational conversation to observe the person’s normal body language. This could be referred to as norming.
Observing changes in physical mannerisms is as important as the actual gestures themselves. Gestures that are typically considered deceptive are covering the mouth with a hand when talking, looking away when speaking, or a change in the tone of the voice. Many times the entire body will change. When a person is asked to talk about something they want to avoid they may slide backward into the chair they are sitting in. I have seen people slide the entire chair backward against a wall to create distance. Crossing the legs and/or arms is an unconscious defensive gesture that might indicate deception. If the interviewer gives hypothetical motives or excuses for an incident the subject will frequently nod the head up and down in agreement. On the other hand, forced efforts to maintain eye contact or intentionally invading the personal space of the interviewer might indicate an effort to appear truthful when telling a lie.
I attended a well known interview and interrogation course early in my career. When my children were small, I used them to learn to observe changes in physical mannerisms. I found it interesting to observe their body language when I asked them who did what around the house. I observed their mannerisms when asking them if they completed their homework, knowing they had not.
While observing body language can be a good investigative tool, I feel obligated to make this disclaimer. Body language is not an exact science. It is a good tool to try and confirm you are on the right track. However, there are various reasons it might not be accurate. People from different cultures have mannerisms that, to the average American, might indicate deception when it is just a normal gesture. People with mental health or drug issues might give indicators that give you the wrong idea. In certain cultures, people are taught not to make eye contact with an authority figure such as a police officer or supervisor. A person might just be nervous or suffer from some type of PTSD or past trauma. My best advice is to try and know your subject. Try to know how they react during normal conversation and be familiar with their culture and how they were raised. Never pass judgement on body language alone. It is but one piece of the investigative puzzle.