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Polygraph Lie Detector FAQ
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If the examinee is nervous, will the polygraph test give a false positive?
Errors are usually referred to as either false positives or false negatives. A false positive occurs when a truthful examinee is reported as being deceptive; a false negative when a deceptive examinee is reported as truthful. Polygraph errors may be caused by the examiner's failure to properly prepare the examinee for the examination, or by a misreading of the physiological data on the polygraph charts.
Can the polygraph be wrong? "No," "However I was just called in by the spouse of a person who failed a pre-employment test. He failed when questioned on cocaine use. His spouse felt sure he had never used cocaine, so how could he fail?
One, he could have lied to her. Two, he might have something about the use of cocaine that bothered him. Perhaps someone used or purchased it in his presence, and it makes him feel uncomfortable. That would show up on the test.
What most people don't realize about a polygraph exam is that the examiner will go over the questions with the examinee several times, making sure there is no area of discomfort. It is vital to the integrity of the test that the examinee be honest about what is bothering them on any given issue before the test. In the case I just mentioned, if perhaps the issue was that someone had used cocaine in this man's presence, the examiner would have phrased the question, with that in mind. For instance, "Other than what you told me, have you ever used cocaine?" If the examinee was honest, the test will show it one way or the other.
A polygraph measures changes in blood pressure, pulse rate, respiration, muscle movements and perspiration. Lying triggers an emotional reaction, and thus a physical reaction which a trained polygraph examiner notes and measures. These reactions fluctuate as a subject responds to a series of questions. Hence, the lie is detected by the polygraph. The objections to the polygraph's use was precisely to that same sensitivity to emotional changes. An attorney can argue the polygraph would not be accurate because their client would to be put in an inherently stressful situation. For instance, that of being tested by a police officer involved in a possible investigation against him.This argument is effective for those without knowledge of the polygraph.
The experienced Examiner is adept at first putting the examinee at ease, as anyone who takes a polygraph test will be nervous. This is expected and looked for by the examiner as totally normal and rarely interfere with the test. The human body has a set of normal patterns. Even though a person has high blood pressure, diabetes, etc., these patterns remain constant. The examiner will take the time needed to chart these "normal" patterns before attempting to determine a lie.
Examiners utilize a variety of procedures to guard against errors by identifing the presence of factors which might cause a false responses; such as:
- an assessment of the examinee's emotional state
- medical information about the examinee's physical condition
- specialized tests to identify the overly responsive examinee and to calm the overly nervous
- control questions to evaluate the examinee's response capabilities
- factual analysis of the case information
- a pre-test interview and detailed review of the questions
- quality control reviews
If a polygraph examinee believes that an error has been made, there are several actions that may be taken including the following:
- request a second examination
- retain an independent examiner for a second opinion
- file a complaint with a state licensing board
- file a complaint with the Department of Labor under EPPA
- file a request for the assistance of the American Polygraph Association
California based agency, local to Southern Califiornia, especially the Los Angeles, Orange County, Riverside, San Gabriel Valley, Pomona Valley, San Bernardino, and Big Bear Areas.
Over 25 years of experience in law enforcement,
interrogation and truth detection.
Martin Schermerhorn, certified polygraph examiner,
has advanced training and is current in the latest techniques, and technologies.
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