The clue to body language of a liar is in his automatic gestures that are not under his control.
When interpreting body language of a liar you should rely on those signs that are not under his cautious control, i. e. gestures and signs that happen automatically. In liar’s case, the least reliable signs are the those that he has most control over, like his words or exposing his palms (exposing palms generally means openness, but in this case can be easily faked).
As it was mentioned in Reading Body Language a small child will instinctively cover her mouth when lying. If she hears something she doesn’t like to hear, she will just cover her ears as if she is trying to block out the sound. If she sees something she doesn’t want to see she would cover her eyes. As she gets elder the face touching gestures become quicker and subtler, but do not disappear altogether.
Face touching gestures will be still there when lying, covering up for someone, exaggerating, doubting or being uncertain. Increased swallowing of saliva is another automatic gesture that is often displayed when lying, but it is usually more noticeable with men than with women.
As it was said in Reading Body Language a separate gesture should not be interpreted without considering other signs that are displayed at the same time and circumstances under which it is happening. The reason for that is that one and the same gesture could mean different things at different times, like for example scratching the head can mean forgetfulness or lying. It could also mean dandruff. Similarly to that, face touching gesture is not always associated with body language of a liar, it could simply mean that the person is just holding back some information. Observing subsequent movements and signs could confirm or deny your suspicions.
Despite that we use our faces to cover up lies and our genuine emotions more than any other body part, they still continuously reveal our true
feelings and attitudes without us being aware of it most of the times. If you are trying to conceal a lie or a certain unpleasant thought flashes into your mind, the evidence will be displayed on your face even for a split second.
For example, if you are on job interview and you are asked about your relationship with the previous boss that you truly hated, but you insist that the relationship was great and you left the job just because you want to have better options for your future, your face will display a sneer at least for a split of a second.
This happens unconsciously and usually goes unnoticed unless the person who is talking to you is highly perceptive to body language. If he is, he will see the contradiction between your verbal and non-verbal signals, and since non-verbal signals have five times more impact than the verbal ones, he is unlikely to believe you.
Lying is not an easy thing to do, because subconscious mind automatically sends signals that are perceived as body language of a liar. They contradict to what the person says and makes his words hard to believe to the one who is listening. These signals include dilation and contraction of pupils, sweating, increased swallowing of saliva, twitching of facial muscles, flushes and increased eye-blinking. It could take a split of a second only, but professional interviewers, sales people and simply perceptive individuals can and do notice these contradictions.
This is the most obvious with those who do not usually lie, because they didn’t refine their body language as “professional” liars do (like actors for example).