Actually, it seems that the face will betray true emotion if we look for it. So, it isn't in the sweaty brow, the hesitant words or the shifty eyes. Instead, it's the liar's facial muscles that "crack” or "leak" through, displaying the real emotion. For more read here
Another technique to test for truthfulness is to ask a person to recall his or her story backwards - From end to beginning in sequential stages. Reverse order is harder to create than building a lie from the start. Telling the story from its end to its beginning will be easy for the truth teller.