Tricky Tilt. Truthful people more likely to face questioners head on. Liars are "likely to lack frontal alignment and will often sit with both their arms and legs crossed as if frozen," says Joseph Buckley, president of John E. Reid and Associates, which provides interview and interrogation training to law enforcement agents.
Imprecise Pronouns. To psychologically distance themselves from the lie, deceptive people often pepper their tales with second- and third-person pronouns like "you," "we," and "they."
Heavy Hands. When people tell the truth, they often make hand gestures that coincide with the rhythm of their speech. Hands emphasize points or phrases--a natural and compelling technique when they actually believe the points they're making. People who are less certain will keep gesticulations in check.
Tongues Like Telephone Wires. The phone tends to bring out the liar in people. In one week-long study of 30 college students, Hancock observed that the phone was the most popular weapon of choice, enabling 37% of the lies told in this time, versus 27% during face-to-face exchanges, 21% using Web-based messaging, and just 14% via e-mail. Little surprise, perhaps: Most phone conversations don't leave a trail, unlike email and instant messages.
Need to Be Right. When honest people tell stories, they may realize they left out some details and backtrack to fill in holes. They also may realize a previous statement wasn't quite right, and go back and explain it further. Liars, says DePaulo, "are worried that someone might catch them in a lie and are reluctant to admit to such ordinary imperfections."
Behavioral Blip. "You're always looking for change from the person's usual baseline," says Paul Ekman, professor emeritus at University of California San Francisco School of Medicine, and manager of Paul Ekman Group, which does training in the area of deception and emotional skills. "Some people always hesitate when they speak. If they speak without hesitation, that's a hot spot."
Detached Smile. People who are telling the truth tend to use many facial muscles. Liars just smile with their mouths--their eyes don't reflect their emotions.