Emotion and facial expressions
When someone is lying, they will do one of three things. A) Show emotion when they have none, B) show no emotion (think of a poker face), or C) mask one emotion with another. Keep a close eye on the person you are speaking to, not just there eyes but also their entire face. Expressions are universal; whether you are a politician or a model your emotionsshow up on you face.
Eyes and upper half vs. Lower half
The upper half of a persons face is a much more reliable measure than the lower half. It generates more involuntary clues and is extremely difficult for someone to control. The muscles used in smiling for example is the most revealing clue to tell if a smile is genuine or manufactured is in the eyes.
Look at the muscles that surround the eye socket. The major muscle running from the cheekbone at an angle to the corner of the lips indicates a sincere smile.
Check for Emotional Leaks
Micro-expressions that flit across the face often expose a person's real thoughts. Imagine if you were to watch people on videotape, frame by frame, you would see them showing their true emotion just before they show the fake expression designed to cover up the lie.This micro expression indicates contempt.
But these ultra-brief facial movements, or micro-expressions, only lasting a fraction of a second, aren't easy to spot. Even professionals trained in lie detection can't always isolate them. And deliberate liars tend to add other expressions, like smiling, to disguise a lie.
If their facial expressions are not in sync with what they are saying. They might be hiding something or lying. For example, if the moment calls for a smile and the smile is delayed or the timing is off.. A genuine smile will crest over their face like a wave.
While most people may interpret darting, unfocused eyes as a classic sign of lying, it's vital to consider the context of the behavior. For example, experienced poker players are careful not to make too much of eye “tells.” People usually look to the left or right when thinking about an answer. Someone not making eye contact should arouse suspicion, but eye contact can be a tricky evaluation tool: Consider that a psychopath can look you in the eye and lie with ease. And in some cultures, it's considered inappropriate to maintain eye contact.
Even though a high percentage of communication is thought to be non-verbal, no single part of the body—such as the eyes or hands—reveals the whole story when it comes to lying. People who are lying often become more still: Hand gestures that normally accompany talking may occur with less frequency or intensity, and there may be fewer arm and leg movements. The person becomes more focused on telling the lie, so they get quieter in their body. A few more examples can be found here.
Ask Follow Up Questions... Quickly
If you suspect you're being lied too, try this technique, which experts say can trip up a liar. Try asking questions quickly—one after the other. “The initial lie is easy,” explains Kang Lee, director of the Institute of Child Study at the University of Toronto, and whose behavioral work with children can often be applied to adults. “The follow-up lie is more difficult. When you continue to ask questions and put people on the spot, it gets harder to maintain the lie.”
Rephrase the Lie Backwards
If you suspect that you are being lied to, ask the person to explain the events leading up to the problem backwards and see if they can get it right! Often, a lie is planned out as a series of events in a certain order leading up to something going wrong. They will have planned the events in a certain order to cover the bases but not the other way round. If it's the truth, then it will be easy to remember. If they are telling the truth then it will be easy!
When a person lies, unless they are a professional liar, will subconsciously try and make themselves small and inconspicuous. As a result, they will often hunch their shoulders, which reinforce their desire to remain small. Watch out for this. Other body gestures include crossing their arms or overtly lean away from you while talking to you.
More info than you asked for
A liar might be so paranoid about being untruthful that they'll offer much more information than you asked for - liars know that a good liar tells more details in order to look innocent. So when your colleague goes off into a tangent about how he never got your message, but he did get a weird message on his answering machine that made him laugh, and that made him think of the other night when... You might have to ask him to revert to the topic at hand. Don't be afraid to ask questions.