Nearly three months ago, Rep. Gary Condit (D-Calif.) submitted to a polygraph test because D.C. police remained skeptical about answers he gave regarding the status of Washington intern Chandra Levy. He passed it with flying colors.
After hearing those results, investigators who trusted the accuracy of the polygraph exam turned their eyes from Condit and began looking into the possibility of a serial killer.
But the police, the Levy family and the media cried foul, decrying not only Condit's refusal to have a licensed government polygrapher administer his test, but also the chance that any polygrapher may have interpreted results inaccurately in past cases.
Because of that, all polygraph tests have been scrutinized as of late, mainly because of the high percentage of possible error, false accusations and possible failure to catch deceptive subjects. The scientific community remains polarized about the reliability of polygraph techniques.
A polygraph examination consists of three phases, which include the pretest interview, the actual test and the collection of charts. If the subject is lying, a post-test is part of the examination.
The polygrapher, or examiner, first gathers information from the investigator, who requested the test. This allows the examiner to create appropriate questions for the actual test. So, for example, if the investigator is the Federal Bureau of Investigation, the examiner asks questions pertaining to one's loyalty to his or her country.
During the first phase, the examiner confirms that the subject understands the instructions for the actual testing phase. Then he tells the subject his legal rights and explains how the polygraph works.
Phase two, the actual test, is where problems could arise. The examiner attaches two pneumograph tubes across the upper chest and abdomen. Pneumograph tubes are metal electrodes that capture heart rate and respiration. Two metal plates also are placed on the ring and index finger to measure the galvanic skin response, the changes in skin perspiration. And a standard blood pressure cuff goes around the upper arm to measure the person's blood pressure.
Because the same machinery has been used in one form or another for 80 years, few argue against the usefulness of the actual polygraph apparatus. But the possibility for error creeps in when the polygrapher must form an opinion about the subject's truthfulness after comparing the physiological reactions to a series of questions.
Polygraph results are only "accurate" when conducted by "trained, experienced personnel," said University Police Department Capt. Michael Coleman.
This is where opponents say the test can be unreliable since human error is possible. Theoretically, when a person is truthful, the body would function within its normal patterns with no significant or consistent changes.
An accurate polygraph test would be able to catch the examinee's tenseness as he focused on the questions that he found most threatening. For example, if he started sweating, the metal plate on his fingertip would measure an increased amount of perspiration when he answered that particular question, thus creating a change in activity on the chart.
"The examiner determines the lie by the tense reaction of the examinee," Psychology Department Chairman Tim Wilson said.
To ensure the examinee's anxieties, the examiner does go over the questions with him several times, and might assess the examinee's emotional state and physical condition before the test begins. This will give him a baseline from which to start the test with. So if a person is already nervous before the test, the examiner takes this into account and doesn't use this against him during the assessment of the exam.
After the collection of charts is concluded, a computer uses an algorithm to score the polygraphs. The examiner also numerically scores the charts. If the examiner, after comparing results with the polygraph, deems the examinee to be truthful, the individual can leave. But if the polygraph results indicate deception, the examiner begins phase three - an interrogation which tries to verify the deceptive test results. But if a mistake was made, it most likely would have occurred during the second phase.
The examiner's expertise and training strongly affect the reliability of the results since their interpretations of an experienced examiner's results would likely be more accurate.
Misinterpretation of the data on the charts, lack of training and experience of the polygraph examiner and a lack of quality control review may cause some of the most frequent polygraph errors.
The American Polygraph Association, defendes the use of the polygraph by sayig it does not consider inconcllusive test results as bad tests and does not hold them against the examinee. They add that considering inconcliusive results as errors is clearly misleading and skews accuracy figures.
But people in the intelligence community remain skeptical because of the polygraph's susceptibility to error. FBI Special Agent Mark Mallah said in a statement, "Its recordings do not measure truth or deception. They measure fluctuations in blood pressure, respiration and sweat response. Period. The examiner then 'interprets' those fluctuations in an attempt to 'infer' truth or deception. Since no physiological pattern is known to be unique to deception, but could also represent anger, fear, anxiety, embarrassment and other emotional states, the interpretations and inferences of the examiner are notoriously prone to error. Entrusting it with the protection of our national security is delusional."
Despite the shortcomings of the polygraph, the federal government continues to administer polygraph examinations on individuals who wish to serve the United States Government. In some cases, courts accept polygraphs as evidence in legal cases.
"The admissibility of a polygraph test requires the permission from the examinee and his or her attorneys," Coleman said.
Because it still is accepted in courts and is an important tool for security agencies, the use of the polygraph continues to be scrutinized.
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