Stephen Parrish is guest-blogging today! His book, The Tavernier Stones, is available now. You can read about it at www.stephenparrish.com. He’s giving away a real, one carat diamond to the first person who can find the image of one he’s hidden somewhere on the web; the contest is described at www.tavernierstones.com.
And today he’s here with us, to
give us advice on tell our characters how to beat a lie detector test:
First of all, I don’t recommend you try, except for fun or research. I’m writing this solely for authors who want to know enough about the subject to put a character through the paces. Also, my experience comes from being in the chair, not from administering the test. Most if not all polygraph technicians believe their tests are reliable, even infallible. Most if not all polygraph technicians want to keep their jobs.
Your perp wants to get off the suspect list. That won’t happen if he refuses to take the test. Remember Scott Peterson? When he refused, the whole country knew he was guilty, and investigators intensified their scrutiny. Your perp is not only willing to take the test, he volunteers for it. He convinces everyone involved¾the investigators, the victim’s family, your readers¾he’s got nothing to hide.
Yet he’s just blown someone’s brains out. "Hook me up," he says. "I’ll prove I wasn’t even there." That’s your first plot point.
Your perp will be seated in a chair and the technician will strap a blood pressure/pulse monitor to his upper arm, rubber tubes across his chest and abdomen, and electrodes to his fingertips. The tubes (pneumographs) will measure his breathing. The electrodes (galvanometers) will measure his sweat production; the more sweat, the less resistance to an electrical current being applied.
There are many different approaches to questioning, but you should keep things simple in your story. In general the technician will ask control questions (What is your address?) and relevant questions (Where were you the night of the murder?) The control questions allow the technician to establish a baseline, with which results of the relevant questions can be compared.
When we lie we experience guilt and fear, which manifest themselves physiologically. Our blood pressure and pulse rise, our breathing increases in frequency and decreases in volume, and we sweat. We also twitch, sigh, grab the arms of the chair, and exhibit other signs of discomfort.
The first time I sat for a test, the technician showed me afterwards that my breathing rate had altered dramatically as I responded to one of the questions; in fact I had caught my breath for a second or two before answering. I told him my answer was nevertheless truthful. He administered the test again, and quite involuntarily I caught my breath again. He judged me to be lying.
It was my first lesson in lie detection theory. Because I happened to be telling the truth.
Lies can in fact be detected by monitoring physiological reactions. A common symptom is not being able to look someone in the eye. Another is sudden involuntary movements; when interrogation tapes are rerun in slow motion, perps are often seen to twitch or make odd facial expressions that happen so fast they go unnoticed at regular speed.
However, we exhibit the same behavior when frightened, angry, jealous, etc. Just because I catch my breath doesn’t mean I’m lying. It just means something about the question, or my answer to it, bothers me. It may also mean something wholly unrelated to the crime at hand occurs to me—a disturbing thought triggered by the question—and I react involuntarily to it. It’s easy to play word association games when someone is interrogating you. In my case, I objected to the question, and thought it was none of the technician’s business.
A polygraph cannot determine whether your perp is lying; it cannot read minds. It can only register physiological reactions during questioning. Reactions can be caused many phenomena other than deceit.
That’s what your perp uses to beat the test.
Of course the polygraph technician knows everything I’ve just said. And any of them who reads what follows will howl with indignation. Fuck ‘em. You need to get your perp off the hook, so he can kill again.
The technician will employ tricks. He’ll tell your perp the test is infallible. He’ll describe a subject he tested yesterday, or an hour ago, who thought he could beat the test and failed. He’ll impress your perp with loads of gadgetry: how could all those wires not be doing their jobs? He’ll ask your perp to tell an actual lie ("I was born in Transylvania") to verify that yes, indeed, the equipment is working properly. He’ll accuse your perp of something he knows he didn’t do, to guage how he reacts while genuinely disputing an allegation.
It’s all mind tricks. It’s all bullshit. The technician can only measure your perp’s blood pressure, pulse, breathing, and sweat production (the latter of which seldom generates useful results). And your perp knows that. He knows that what the technician is ultimately after is a confession. Unlike the test, a confession is admissible in court.
At the end of the test the technician will show your perp the results and point out the lies. The average person, when lying, and when confronted with physical evidence of it, will cave in. That’s why polygraphs are effective, and why government agencies like the CIA employ them routinely on their own people. It goes without saying, then, that your perp must never confess to anything, no matter what evidence is presented; no matter how squiggly the lines appear on the graph. Yet he can’t clam up. That’s just as bad as refusing to submit in the first place.
Let’s say he molested a child. (Yeah, I know, he was first accused of murder, but pretend the victim recovered.) If it were me in the chair, any question about child molestation would be troublesome, because I have a child. Any question about breaking and entering would be troublesome, because I was once robbed, and the experience made me feel violated. And question about insider trading would be troublesome, because I’ve thought about doing it, and I feel guilty about that. It takes preparation: your perp must predict every possible question that might cause a blip in the graph, and be ready to explain it. Ironically, if he’s the one who committed the crime, that shouldn’t be a problem. (He has to be fast on his feet as well, but you can be slow, because your manuscript isn’t due for another month.)
What your perp really wants, of course, is for no blip to appear at all.
Assume he’s going to have a physiological response to the question, "Are you telling the truth about where you were the night of the murder?" (The victim nearly pulled through, but then took a turn for the worse.) Your perp, because he’s a cold-blooded killer, will have much less of a reaction than Dudley Dooright. Still, the graph will do that zig-zag thing it does, and he needs to flatten the zigs and zags.
First, he maintains a high level of anxiety throughout, by breathing more shallowly and rapidly than normal, by gripping and regripping the arms of the chair, by shifting his weight regularly. If he goes too far the technician will admonish him and possibly report him as "uncooperative." It has to be subtle. Just enough to make him come across as high strung.
Second, and this is the key, he must be prepared to subtly overreact during honest answers, to counter a natural tendency to relax. If he catches his breath when he doesn’t like something, as I do, then he should catch his breath before answering every question, honestly or dishonestly, to obscure the difference. Whatever he does when he lies, he does while telling the truth. During at least one honest answer ("Are you telling the truth about your place of birth?") he should flinch ever so slightly. And I’ll leave the reason why as a homework assignment.
It takes practice. And experience. Given a modicum of each, most people reading this post could do it. Your perp certainly can; he’s been down this road before.
If you’re a crime writer I recommend you make an appointment with a local polygraph service and experience all this for yourself. They’re in the yellow pages. Just explain you’re doing research for a story, and provide the facts of the case, including story elements you know to be false. Pretend you’re the perp. And let me know how it goes.
Great guest post, huh? Now go buy his book, The Tavernier Stones. And watch Steve’s blog: there’s a killer Scrabble war going on that’s not to be missed. It’s intense. I’m scared to say who I’m rooting for. You?