With TV shows like 24 and Lie to Me on the air, it's a good time to learn how to tell if someone is lying. Gary Berntson, a professor of psychology, psychiatry and pediatrics at Ohio State University, offered some hints. Berntson cited the work of Paul Ekman and Guillaume Duchenne as he explained how to become a human polygraph.

With TV shows like 24 and Lie to Me on the air, it's a good time to learn how to tell if someone is lying. Gary Berntson, a professor of psychology, psychiatry and pediatrics at Ohio State University, offered some hints. Berntson cited the work of Paul Ekman and Guillaume Duchenne as he explained how to become a human polygraph.

1. Look for the false smile

When people grin naturally, as an outflow of legitimate emotion, their eyebrows lower and their cheek muscles pull the corners of the mouth apart, sometimes causing crow's feet. A false smile may or may not have the crow's feet, but it almost never will include a lowered brow.

2. Notice nervous tics

A lie can be plastered all over the perpetrator's face. Changes in breathing, dilated pupils, sweating or increased blinking are telltale signs of fraud.

3. Check the body language

The mouth and the body are often not on the same page. A witness might answer with a definitive "no" while subconsciously gesturing with an affirmative nod.

4. Extreme alibis are a red flag

Liars can conceal - withholding crucial information - or simply distribute false information. It's easier to spot a falsifier, particularly when they go too far, answering with an overly detailed spiel when a simple "yes" or "no" would do.

5. Don't jump to conclusions

Polygraphs don't detect lies. They detect the physiological reactions that often accompany lies. In the same way, these tips are good guidelines, but they're hardly foolproof. Take great pains to avoid the Othello Error, named for the Shakespearian tragic hero who killed his faithful wife when she responded emotionally to his accusations of infidelity.