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The cop pulled over a brand new BMW for speeding and asked the driver for his license and registration. The driver, a well-dressed, well-groomed man in his 40’s smiled. “I don’t have either, officer,” he said with sincerity. “I just bought the car, and left my wallet in the pants I dropped off at the cleaner yesterday. I’m actually going to get the wallet now.”

The officer found the story very believable….until the driver, smoking an elegant Dunhill, flicked ash on the carpet.

Pulling his automatic, the officer ordered the man to put his hands on the wheel, then opened the door and cuffed him. When he called in the “VIN” number on the BMW’s dashboard he found that the car was stolen.

The officer knew something was amiss because he had learned good indicators of suspects lying. In this case, the indicator was a contradiction: Owners of brand new BMWs don’t drop ashes in their prized possessions.

You can learn indicators of deception, too, even without police training. We have all heard about behavioral “tells," but some are actually quite unreliable. For example:

1. Shifty eyes or lack of eye contact. People do this for lots of reasons—distraction, for example.
2. Embellishing excuses. For example, someone explaining why they're three hours late getting home with more detail than it seems is necessary. But some people are just wordy.
3. Fidgeting, such as jittery legs and moving hands. I fidget constantly, especially when telling the truth. How about you?
4. Tugging on ear lobes. Sometimes, ears itch.
5. Fast speech, lots of uhs and ums, and frequent pauses. And some of us just aren’t very articulate.
6. Loud speech. Maybe the room is noisy.
7. Change in heart rate, blood pressure, or galvanic skin response. You can’t measure these without a polygraph, but don’t bother buying one and hooking someone up to it. There’s no solid evidence that lie detectors sense anything more than changes in physiological arousal. 

Behavioral research, however, reveals some indicators that do have some ability to detect deception. These 7 are far from perfect, so your mileage may vary:

1. The individual moves his hands and fingers less than normal while talking.
2. The individual uses fewer gestures than usual to illustrate his points.
3. The individual exhibits “leakage” of facial expressions. Paul Ekman calls these “micro-expressions” and they can creep out under stress. For example, a man might ever-so-slightly shake his head “no” when answering “yes" (or the other way around).
4. The individual's pupils get bigger than normal when he answers a question like, "Did you enjoy the piano recital?” (You’ve got to be super observant to pick these cues up, because they’re subtle.)
5. The individual's voice gets more stressed. (Ditto the super-observant caveat here; voice stress analysis usually takes sophisticated computers.)
6. Your gut feeling. People watching interrogations of suspects report that monitoring the interrogator’s reaction to a suspect’s answers can be a better indicator of lying than watching the suspect himself. Gut feelings aren’t always right, of course, but they can be useful when used with other indicators.
7. Contradictions. As with the stolen BMW, statements that don’t add up, or are inconsistent with other statements, suggest deception. Police officers ask suspects the same question different ways to tease out such contradictions. The truth hangs together, lies do not, as Sir Walter Scott famously observed

“Oh the intricate web we weave, when first we practice to deceive”

So now you have a few tools to help you unravel his web of deception. But proceed with caution: Webs of truth can be just as sticky as webs of lies!

https://fas.org/irp/dni/educing.pdf