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Nervousness is not an impediment either. Examiners want their subjects to be somewhat nervous. But that doesn't affect the results of a polygraph, because when a person lies, his reactions, as captured on the polygraph charts, differ from the reaction caused by nervousness.
A polygraph compares a person's reaction to questions an examiner knows the subject is lying about with questions an examiner is not sure about. The most crucial part of the exam takes place in the lengthy pretest interview. During this segment, Holden gains the subject's trust, discusses the facts of the case, formulates test questions with the subject, and alternately puts the subject at ease and makes him acutely aware of the consequences of the test. It is important that the examiner stay neutral: "If you accuse, you lose," Holden tells the classes he teaches at the Department of Public Safety's Law Enforcement Polygraph Academy, where he is on the teaching faculty.
Next, he hooks the subject up to the polygraph machine and asks a series of questions. One set of questions is neutral and nonthreatening, designed to cause little physiological reaction. The second set, called control questions, is designed to get the subject to purposely lie about something significant. This is tricky but crucial to obtaining accurate test results. Finally, Holden asks between two and five carefully honed questions pertaining to the issues in a case he's helping to resolve.
It is imperative that the questions not be ambiguous or open-ended, and not leave any loopholes or room for interpretation. (You can bet if Holden were questioning President Clinton about having sexual relations with Monica Lewinsky, he would have nailed down the definition of sex with Clinton first.)
After carefully evaluating and scoring the charts showing a subject's reaction pattern to the questions, Holden renders an opinion about whether a subject is being truthful or not. Sometimes the results can be inconclusive. Before sending the results to a client, he shows the charts to one or two other in-house examiners as part of routine quality control. In particularly high-profile or controversial cases, he sends the data--minus his conclusions--to top experts around the country to corroborate his findings.
Do two reputable examiners ever look at the same results and come to different conclusions? "Yes, it happens," Holden admits, "but if it is a disagreement among professionals, it means there is a mistake in the data, and we'll find it. Maybe it is a bad test question or an improper interview."
Holden is asked whether he has ever seen a case in which someone is examined by two reputable examiners who follow standardized procedures and ask the same questions, but who come up with different conclusions.
"Never," he says.
Even if the procedures are followed to the letter, however, a polygraph is only as worthwhile as the questions asked. Nothing illustrates that point better than the lie-detector test Darin Routier failed last spring.
A jury convicted Routier's wife, Darlie, of murdering their two sons in the couple's Rowlett home, but many people, including Waco businessman Brian Pardo, refused to believe she was guilty. In an effort to help get her conviction overturned, Pardo asked Darin Routier to submit to a polygraph in order to exclude him as a suspect.
Without seeing videotape of the testing session and a copy of the polygraph charts, Holden has no way of knowing if the test was administered properly. But even a layperson could tell that the questions the examiner put to Routier--a copy of which was obtained by the Dallas Observer--weren't specific enough to determine what, if any, role he had in the boys' murder.
Routier was asked the following: Were you involved in any plan to commit a crime in your home in June 1996? Did you, yourself, stab Darlie on June 6, 1996? Do you know exactly who left the sock in the alley? (A blood-stained sock from the home was found in an alley nearby. Police believe it was placed there to make it appear as though the boys' killer fled the house.) Can you name the person who stabbed your sons?
The examiner reported that Routier was deceptive when he answered "no" to each question. Beyond indicating that Routier knew more about what happened that night than he ever let on--which the prosecutors have suspected all along--the only additional information the test suggests is that Routier stabbed his wife. It's a juicy tidbit, but what does it mean? Did he stab her as part of an attempt to cover up the murder? Could he have stabbed her while she was sleeping without her knowledge?
The exam is ultimately useless, for it raises far more questions than it answers--a cardinal polygraph sin.
For most of this century, the judicial system's prevailing view of lie detector tests was that they existed in the twilight zone of scientific acceptance. That was the conclusion a federal court of appeals came to in 1923. That opinion kept polygraph-examination testimony out of the courtroom until 1989, when the 11th U.S. Circuit Court of Appeals concluded that lie detectors had gained general acceptance in the scientific community. The decision allowed for them to be entered as evidence in trials in a few, limited circumstances.