Navarro, Joe, Schafer, John R., The FBI Law Enforcement Bulletin
The young mother leaned back and cleared her throat. Her eyes teared and her voice quivered as she explained how her baby disappeared. Her clasped hands trembled slightly and her feet pointed toward the door. Her demeanor appeared too subdued. Reluctant to call the mother a liar, the investigator asked her if she had a reason to lie. She answered, "I never lie. My mother taught me always to tell the truth." The investigator had seen and heard enough--he asked the woman to take a polygraph examination. During the postpolygraph interview, the woman confessed that she had suffocated her baby. Both her verbal and nonverbal behaviors had revealed the gruesome truth.
From heated knife blades across the tongue to electric prods, people have sought ways throughout history to test the truthfulness of others. Fortunately, researchers in criminology and psychology have identified verbal and nonverbal behaviors that detect deception in a more humane manner. Nonetheless, detecting deception remains a difficult task. In fact, multiple studies have found that lie detection, like a coin toss, represents a 50/50 proposition, even for experienced investigators.  Although detecting deception remains difficult, investigators increase the odds for success by learning a few basic nonverbal and verbal cues indicative of lying.
Lying requires the deceiver to keep facts straight, make the story believable, and withstand scrutiny. When individuals tell the truth, they often make every effort to ensure that other people understand. In contrast, liars attempt to manage others' perceptions.  Consequently, people unwittingly signal deception via nonverbal and verbal cues.  Unfortunately, no particular nonverbal or verbal cue evinces deception. 
Investigators' abilities to detect deceptive behavior depends largely on their ability to observe, catalogue, and differentiate human behavior. They must identify clusters of behavior, which cumulatively reinforce deceptive behaviors unique to the person the person interviewed.  Investigators also should learn to formulate questions to facilitate behavioral observations. The more observations investigators make, the greater the probability of detecting deception. For the most part, family members and close friends display patterns of genuine openness. For inexperienced investigators, these behavioral patterns may serve as a comparative reference for contrast with deceptive behaviors.
The Interview Setting
The ideal setting for an interview places the interviewee in a position where no obstacles, such as tables or desks, block the interviewer's full view of the subject's body. A large portion of nonverbal behaviors emanates from the lower body, not just from the hands and face. Feet that fidget or point to the door communicate discomfort.  If subjects sit behind a desk or table, officers should encourage them to relocate. Deceivers often use soda cans, computer screens, and other objects, both large and small, to form a barrier between themselves and investigators.  Objects used in this manner create distance, separation, and partial concealment--behaviors consistent with dishonesty.
Many investigators rely too heavily on eye contact. Research indicates that people, especially frequent liars, actually increase eye contact because they learned that investigators often gauge veracity by strong eye contact.  Nevertheless, eye aversion during difficult questions, as opposed to benign questions, can depict distress.
Eyes do not just see, they communicate when the brain conducts internal dialog, recalls past events, crafts answers, or processes information. Eyes also serve as a blocking mechanism, much the same way as folded hands across the chest or turning away in disagreement. When people hear or see something they disagree with or do not fully support, their eyelids tend to close longer than a normal blink. …