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A polygraph (commonly yet incorrectly referred to as a lie detector) is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration and skin conductivity while the subject is asked and answers a series of questions. The polygraph measures physiological changes caused by the Sympathetic Nervous System during questioning. Within the Federal Government, a polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination.
Today, polygraph examiners use two types of instrumentation, analog and computerized. In the United States, most examiners now use computerized instrumentation.
A typical polygraph test starts with a pre-test interview to gain some preliminary information which will later be used for "Control Questions", or C. Then the tester will explain how the polygraph is supposed to work, emphasizing that it can detect lies and that it is important to answer truthfully. Then a "stim test" is often conducted: the subject is asked to deliberately lie and then the tester reports that he was able to detect this lie. Then the actual test starts. Some of the questions asked are "Irrelevant " or IR ("Is your name Rob T?"), others are "probable-lie" Control Questions that most people will lie about ("Have you ever stolen money?") and the remainder are the "Relevant Questions ", or R, that the tester is really interested in. The different types of questions alternate. The test is passed if the physiological responses during the probable-lie control questions (C) are larger than those during the relevant questions (R). If this is not the case, the tester attempts to elicit admissions during a post-test interview ("Your situation will only get worse if we don't clear this up").
While some people believe that polygraph tests are reliable, there is little scientific evidence to support this claim. For example, while some claim the test to be accurate in 90% - 95% of the cases, critics charge that rather than a "test", the method amounts to an inherently unstandardizable interrogation technique whose accuracy cannot be established. A 1997 survey of 421 psychologists estimated the test's average validity at about 61%, a little better than chance. Critics also argue that even given high estimates of the polygraph's accuracy a significant number of subjects (e.g. 10% given a 90% accuracy) will appear to be lying, and would unfairly suffer the consequences of "failing" the polygraph. In the 1998 Supreme Court case, U.S. v. Scheffer, the majority stated that “There is simply no consensus that polygraph evidence is reliable” and “Unlike other expert witnesses who testify about factual matters outside the jurors' knowledge, such as the analysis of fingerprints, ballistics, or DNA found at a crime scene, a polygraph expert can supply the jury only with another opinion…”. Also, in 2005 the 11th Circuit Court of Appeals stated that “polygraphy did not enjoy general acceptance from the scientific community”. Polygraph tests have also been criticized for failing to trap known spies such as double-agent Aldrich Ames, who passed two polygraph tests while spying for the Soviet Union. Other spies who passed the polygraph include Karl Koecher, Ana Belen Montes, and Leandro Aragoncillo. Noted pseudoscience debunker Bob Park recently commented, "The polygraph, in fact, has ruined careers, but never uncovered a single spy."
Several countermeasures designed to pass polygraph tests have been described, the most important of which is never to make any damaging admissions. Additionally, several techniques can be used to increase the physiological response during control questions. Asked how he passed the polygraph test, Ames explained that he sought advice from his Soviet handler and received the simple instruction to: "Get a good night's sleep, and rest, and go into the test rested and relaxed. Be nice to the polygraph examiner, develop a rapport, and be cooperative and try to maintain your calm."]
Modus operandi (often used in the abbreviated forms MO, M.O. or simply Method) is a Latin phrase, approximately translated as "mode of operation". The plural is modi operandi ("modes of operation"). It is used in law enforcement to describe a criminal's characteristic patterns and style of committing crimes. It is also applied in fraud investigation when talking about behavior patterns that indicate specific types of fraud, e.g., "False identity is a key MO of retail banking sleeper fraud".
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