Look for Details that Don't Fit
Israeli airport security officials famously rely more on questioning and less on sophisticated scanners to intercept terrorists, fugitives and other people they want to keep off planes. They'll scan a traveler and look visually for things that don't match the person's story, and/or ask the same question in a couple of different ways, looking for inconsistencies in the answers. The Israelis are so relentlessly probing that some tour groups have given their members lengthy briefings in advance, on how not to flub answers nervously and trigger an even lengthier back-room interrogation [source: Parker].
FBI interrogators have their own version of this technique, called statement analysis, which is based on research showing that a person's choice of words may change distinctively when he or she slips a deceptive statement into a narrative. They've discovered, for example, that a person who is lying may suddenly start leaving out the pronoun "I" and start using "we" instead. Additionally, a change in the choice of verb tense may indicate a deception. For instance, Susan Smith tearfully pleaded on TV for the return of her "abducted" children, saying, "They needed me." Police later determined she had deliberately drowned them -- which of course she knew at the time she made the plea. Hence, the past tense.
Another warning sign to investigators is when an interview subject uses an odd or inappropriate choice of words, such as using the word "startled" to describe having a knife held at her throat by an assailant, rather than "terrified" [source: Adams]. These kind of slip-ups are easier to pick out in written statements, but if you're a careful listener, you can train your ear to catch subtle mistakes that may indicate that you're being lied to.