How to :
1. Look for deceptive behaviors and responses within the first five seconds after asking a question.
2. If what they say is the truth, they will say immediately and plainly that they did not commit the crime.
3. Liars often respond to questions with truthful statements that cast them in a favorable position.
4. Liars often repeat a question to stall for time.
5. Nonverbal cues to lying include hiding the mouth or eyes, throat clearing or swallowing, grooming gestures like adjusting shirt cuffs, shifting weight around and sweating.
6. Liars often go into attack mode against the questioner or butter up the questioner with compliments.
source : http://www.forbes.com/sites/susanadams/2012/08/13/how-to-tell-when-someone-is-lying
