Liars have things too much their own way. They choose how they lie and when they lie, so they have all the time in the world to rehearse their stories. They can pick the moment when you’re psychologically most vulnerable. The most important way to detect lying is to listen for inconsistencies. But this is a passive method that relies on waiting for the liar to make a mistake. Active questioning gives the initiative back to the lie detector. Questioning is the art of interrogation. One drawback of asking questions is that it reveals what the questioner doesn’t know. For that reason, experienced interrogators usually mix in questions that they already know the answer to in order to confuse the liar about the gaps in their knowledge. Also, asking a question to which you know the answer gives the interrogator a baseline for later comparison: how the subject behaves when the interrogator knows he’s telling the truth and the behavioral characteristics he reveals when the interrogator knows he’s lying. Many people who are learning interview technique think that the phrasing of a question is key. Of course the choice of words—precise, wriggle-proof words (see Liar Tip-Off #10 Weasel Words)—are important, but the timing of the question is more important. The liar will usually have rehearsed not only what he’s going to say, but also what you’re going to say, the context in which he’ll tell his lie, and the lines that lead up to the lie. He’s prepared himself like an actor learning his lines. He’s expecting he’ll lead into the lie—in other words, he’s expecting that he’ll be allowed to lie on his own terms. Or else he expects that you’ll cue the lie with a question he’s prepared for: “Where were you last night?” “I’m glad you asked me that, because something really peculiar happened…” The good interrogator will disrupt the liar’s game plan. Skilled interviewers lull the subject. Some experts talk about gaining the trust of the person who’s being interrogated, but I think this is nonsense. Most people you need to interrogate aren’t capable of trust, and even if they were, who needs it? All that’s necessary is to lower the liar’s index of suspicion. Don’t be drawn into the hot topic on his terms, at the time of his choosing. “I didn’t get in till late last night.” “I went to bed early and slept like a log. You look tired. More coffee?” Disrupt his game plan. Hold back The Big Question. Change to a neutral topic (but segue, don’t give away your strategy by making the switch blatant). Lull him. Lead him to the conclusion that his deception has been successful. Get him to drop his guard. Move him out of the area he’s rehearsed (and you haven’t). Remove him from lying mode. Get the liar at a point of psychological vulnerability.  Then ambush him with The Big Question.
By this time, you’ll have had time to phrase it just right. You might even have time to rehearse what you’re going to say. The important thing is this: There is no such thing as “No comment.” When you ask the question at a moment when the liar isn’t expecting it, when he isn’t prepared and rehearsed, you will get an answer. A well-timed question is like a slap in the face. However well the liar is prepared, he will flinch when it’s delivered. He may try to clam up. “I don’t want to discuss that right now.” Even if he refuses to answer, you will get an answer. When you ask The Big Question, don’t waste precious processing capacity listening to what he says. Words don’t matter here. Words are garbage liars throw out to confuse you. Instead, pay attention to censor hesitation: This is when the liar starts to say one thing, then retracts it and says something else instead. Watch his lips: In censor hesitation, they open and start to form the first word, then close as this first attempt is censored, then form the word he actually speaks. Pay attention also to eye movements (see Liar Tip-Off #7 Snake Eyes) that indicate the liar is activating more brain regions than he ought to need if he’s telling you something that really happened. Watch for hand movements (see Liar Tip-Off #5 Ten Soldiers of the Face), or telltale changes in posture (see Liar Tip-Off #3 The Axis of Empathy). The art of interrogation is the lead-up to The Big Question. Properly phrased, properly prepared, there’s no way he can avoid it. Go ahead: Set him up!
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