There are, however, basic observable signals that show when people are conscious of something wrong in what they are saying. The ordinary liar gives out such signals without being aware of it. The body has some automatic ways of reacting when what is being said contradicts to what the mind knows.
When a person says something that he knows to be untrue, a number of things are obvious. He will show signs of nervousness. His body will make it difficult for him to speak. He may, for instance, put his fingers slightly across his mouth, as if to stifle the words. He may, also, keep looking away like he wants to divert the focus of the conversation.
Even if he may be able to keep his hands still, his throat muscles may constrict so that you may notice a slight vocal tremor or rise in pitch. There will be some discrepancy in his speech. He may stutter, hesitate, mumble, switch words or sentences around, or his talk disjointed altogether, switching halfway from one phrase and then to another.
A liar who's aware of all these involuntary signals may try to mask them. He may deliberately control his body language. Knowing that restlessness is a telltale sign of lying, he may stand unusually motionless, use fewer gestures than usual, and keep his expression fixed. Particularly, he may keep his hands turned inwards. Studies suggest that it is easier for people to tell a lie if the palms of their hands are held downwards and out of view.
The liar may also try to conceal his jitters by maintaining direct eye contact and a bright smile. The smile, though, often comes apparently fake, involving the lips but does not reach the muscles around the eyes. The eyes can be eerily penetrating, as if searching whether the other fellow has a hint of what's going on. Underneath all this masking, the liar nevertheless sends out all kinds of nervous signals, out of anxiety of being uncovered. These signs are sometimes not easily seen, and do not appear at all in those parts of the body that are most visible, such as the face. But they are there, always; although it takes a keener eye to spot the slips of a clever sham.
But somewhere away from the poker face the liar's fingers may be fidgeting, his toes twitching, his feet tapping as if raring to escape. The liar may have uneven breathing, a tendency to clear his throat repeatedly, a sudden change in skin color, or a dry mouth that causes him to lick his lips more often. The unconscious, uncontrollable signals of stress, from the nervous system, will always find their way to the surface.
One caution though-these same signals can sometimes show up for reasons other than that the person is lying. He may be telling the truth but is apprehensive that his revelation will be unwelcome. He may be telling the truth but not really want to be telling it. Or, he may be telling the truth but not in its entirety.
If you suspect that someone is lying, there is a way to get to the bottom of things. Move closer, face the suspect directly, get eye contact, and take on a serious, scrutinizing expression. Ask probing questions. Be observant of signs of stress as he answers. If your doubt persists, continue asking or rephrase your questions and ask them again. Eventually, you may hear the truth.