Watch his movements.
The eyes aren’t just windows to the soul, they’re windows to the subconscious mind and you can study them to determine whether someone is being honest. An honest person will feel comfortable making eye contact with you while a liar may find it very difficult to look you in the eye. If someone is being honest, his pupils will remain dilated as he speaks. A liar’s pupils will involuntarily become smaller due to the stress of lying and the fear of being caught.
Pay attention to his language.
Because lying requires a lot of concentration, a liar may not be as aware of his body language as an honest person might be. Note the position of the hands and arms as he talks to you. An honest person won’t cross his arms or back away from you as he speaks. A liar may try to cover his mouth, or heart, or place something between the two of you as a means of “covering” the lie. You can tell if someone is being honest by how animated he appears to be. A liar may talk with his hands as a means of speeding the conversation along. However, you can’t use animated body language as evidence of a lie if the person is normally very animated or speaks with his hands during normal conversations.
Note his facial expressions.
If someone is being honest with you, his facial expressions will match his dialogue; however, there will be a slight delay in the facial expressions of a liar. Because lying requires a great deal of thought, a liar may not be able to match his speech with the appropriate facial expression until a few seconds later. Only after a liar succeeds at telling a convincing lie will he convey a facial expression to match his words.
Someone who’s being honest will use contractions when he or she speaks--a liar may not. Using the contractions “I didn’t” or "I wasn’t” shows a relaxed state of thinking. The absence of contractions in speech shows a defensive thought pattern. If a person is being honest, he will have no reason to become defensive when questioned about his actions. A liar’s speech may be garbled or quieter than usual and he may mispronounce words as he concentrates on telling a convincing lie. If someone stutters, stammers, or mumbles more than usual, he is probably lying.
Change the subject and watch his reaction.
An honest person, who has nothing to hide, may be confused as to why you changed the subject so abruptly while a liar will welcome the change. A liar may look relieved, let out a sigh, or smile frequently after the pressure is off and he thinks the lie was successful. If someone is being honest, he will eventually bring the subject up again. A liar will drop the subject altogether.
- Ask questions about minute details and watch a liar squirm as he tries to build around the lie.
- Any deviation from a person’s normal attitude and mannerisms may indicate he is lying.