A polygraph (popularly 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, on the theory that false answers will produce distinctive measurements. The polygraph measures physiological changes caused by the sympathetic nervous system during questioning. Within the US federal government, a polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination. Several other technologies are also used in the field of lie detection, but the polygraph is the most famous. An example of a different method which is commonly used is a device which monitors the response of the individual's eye. If the iris contracts suddenly, this could indicate that the person is lying.
Polygraphs are often used as an interrogation tool with criminal suspects or candidates for sensitive public or private sector employment. The use and effectiveness of the polygraph is controversial, with the manner of its use and its validity subject to increasing criticism.
Early devices for lie detection include an 1885 invention of Cesar Lombroso used to measure changes in blood pressure for police cases, a 1914 device by Vittorio Benussi used to measure breathing, and an abandoned project by American William Marston which used blood pressure and galvanic skin response to examine German prisoners of war.
A device recording both blood-pressure and galvanic skin response was invented in 1920 by Dr. John A. Larson of the University of California and first applied in law enforcement work by the Berkeley Police Department under its nationally renowned police chief August Vollmer. Further work on this device was done by Leonarde Keeler.
Makenzie wrote a second paper on the concept in 1915, when finishing his undergraduate studies. He entered Harvard Law School and graduated in 1918, re-publishing his earlier work in 1917. According to their son, Marston's wife, Elizabeth Holloway Marston, was also involved in the development of the systolic blood-pressure test: "According to Marston’s son, it was his mother Elizabeth, Marston’s wife, who suggested to him that 'When she got mad or excited, her blood pressure seemed to climb' (Lamb, 2001). Although Elizabeth is not listed as Marston’s collaborator in his early work, Lamb, Matte (1996), and others refer directly and indirectly to Elizabeth’s work on her husband’s deception research. She also appears in a picture taken in his polygraph laboratory in the 1920s (reproduced in Marston, 1938). The comic book character, Wonder Woman by William Marston (and influenced by Elizabeth Marston ) carries a magic lasso which was modelled upon the systolic blood-pressure test.
Marston was the self proclaimed “father of the polygraph” despite his predecessor's contributions. Marston remained the device's primary advocate, lobbying for its use in the courts. In 1938 he published a book, The Lie Detector Test, wherein he documented the theory and use of the device. In 1938 he appeared in advertising by the Gillette company claiming that the polygraph showed Gillette razors were better than the competition.
A typical polygraph test starts with a pre-test interview to gain some preliminary information which will later be used for "Control Questions", or CQ. 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 Michael Legaspi?"), 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 RQ, 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 (CQ) are larger than those during the relevant questions (RQ). If this is not the case, the tester attempts to elicit admissions during a post-test interview, for example, "Your situation will only get worse if we don't clear this up".
Criticisms have been given regarding the validity of the administration of the Control Questions test (CQT). The CQT may be vulnerable to be conducted in an interrogation-like fashion. This kind of interrogation style would elicit a nervous response from innocent and guilty suspects alike. There are several other ways of administrating the questions.
An alternative is the Guilty Knowledge test (GKT), or the Concealed Information Test (CIT). The administration of this test is given to prevent potential errors that may arise from the questioning style. The test is usually conducted by a tester with no knowledge of the crime or circumstances in question. The administrator tests the participant on their knowledge of the crime that would not be known to an innocent person. For example: “Was the crime committed with a .45 or a 9 mm?” The questions are in multiple choice and the participant is rated on how they react to the correct answer. If they react strongly to the guilty information, then proponents of the test believe that it is likely that they know facts relevant to the case. This administration is considered more valid by supporters of the test because it contains many safeguards to avoid the risk of the administrator influencing the results.
Although the CQT [Control Question Test] may be useful as an investigative aid and tool to induce confessions, it does not pass muster as a scientifically credible test. CQT theory is based on naive, implausible assumptions indicating (a) that it is biased against innocent individuals and (b) that it can be beaten simply by artificially augmenting responses to control questions. Although it is not possible to adequately assess the error rate of the CQT, both of these conclusions are supported by published research findings in the best social science journals (Honts et al., 1994; Horvath, 1977; Kleinmuntz & Szucko, 1984; Patrick & Iacono, 1991). Although defense attorneys often attempt to have the results of friendly CQTs admitted as evidence in court, there is no evidence supporting their validity and ample reason to doubt it. Members of scientific organizations who have the requisite background to evaluate the CQT are overwhelmingly skeptical of the claims made by polygraph proponents.
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. Pseudoscience debunker Bob Park said, "The polygraph, in fact, has ruined careers, but never uncovered a single spy." Polygraph examination and background checks also failed to detect Nada Nadim Prouty, who was not a spy but was convicted for improperly obtaining US citizenship and using it to obtain a restricted position at the FBI.
Prolonged polygraph examinations are sometimes used as a tool by which confessions are extracted from a defendant, as in the case of Richard Miller, who was persuaded to confess largely by polygraph results combined with appeals from a religious leader.
Other suggested countermeasures include for the subject to mentally record the control and relevant questions as the examiner reviews them prior to commencing the interrogation. Once the interrogation begins, the subject is then supposed to carefully control their breathing during the relevant questions, and to try to artificially increase their heart rate during the control questions, such as by thinking of something scary or exciting or by pricking themselves with a pointed object concealed somewhere on their body. In this way the results will not show a significant reaction to any of the relevant questions.
The accuracy of the polygraph has been contested almost since the introduction of the device. In 2003, the National Academy of Sciences (NAS) issued a report entitled “The Polygraph and Lie Detection”. The NAS found that the majority of polygraph research was " Unreliable, Unscientific and Biased" (quote). The NAS study identified 57 of the 80 odd research studies that the APA relies on, to come to their conclusions. These studies concluded that a polygraph test regarding a specific incident can discern the truth at “a level slightly greater than chance, yet short of perfection”. The report also concluded that this level of accuracy was overstated and the levels of accuracy shown in these studies "are almost certainly higher than actual polygraph accuracy of specific-incident testing in the field.”
When polygraphs are used as a screening tool (in national security matters and for law enforcement agencies for example) the level of accuracy drops to such a level that “Its accuracy in distinguishing actual or potential security violators from innocent test takers is insufficient to justify reliance on its use in employee security screening in federal agencies.” In fact, the NAS extrapolated that if the test were sensitive enough to detect 80% of spies (a level of accuracy which it did not assume), in a hypothetical polygraph screening of 10,000 employees including 10 spies, 8 spies and 1,598 non-spies would fail the test. Thus, roughly 99.6 percent of positives (those failing the test) would be false positives. The NAS concluded that the polygraph “...may have some utility” but that there is "little basis for the expectation that a polygraph test could have extremely high accuracy.
In the United States, the State of New Mexico admits polygraph testing in front of juries under certain circumstances. In many other states, polygraph examiners are permitted to testify in front of judges in various types of hearings (Motion to Revoke Probation, Motion to Adjudicate Guilt).
In 2007, in Ohio v. Sharma, an Ohio trial court overruled the objections of a prosecutor and allowed a polygraph examiner to testify regarding a specific issue criminal examination. The court took the position that the prosecutors regularly used polygraph examiner to conduct criminal tests against defendants, but only objected to the examiner's testimony when the results contradicted what they hoped to achieve. Dr. Louis Rovner, a polygraph expert from California, tested the defendant and testified as an expert witness both at a pretrial admissibility hearing and at trial. The defendant, who had been charged with sexual battery, was acquitted.
The Court cited, with approval, the Canadian case of Phillion v R 1978 1SCR 18.
It is difficult to precisely determine the effectiveness of polygraph results for the detection or deterrence of spying. Failure of a polygraph test could cause revocation of a security clearance, but it is inadmissible evidence in most federal courts and military courts martial. The polygraph is more often used as a deterrent to espionage rather than detection. One exception to this was the case of Harold James Nicholson, a CIA employee later convicted of spying for Russia. In 1995, Nicholson had undergone his periodic five year reinvestigation where he showed a strong probability of deception on questions regarding relationships with a foreign intelligence unit. This polygraph test later launched an investigation which resulted in his eventual arrest and conviction. In most cases, however, polygraphs are more of a tool to "scare straight" those who would consider espionage. Jonathan Pollard was advised by his Israeli handlers that he was to resign his job from American intelligence if he was ever told he was subject to a polygraph test. Likewise, John Anthony Walker was advised to by his handlers not to engage in espionage until he had been promoted to the highest position, for which a polygraph test was not required, to refuse promotion to higher positions for which polygraph tests were required, and to retire when promotion was mandated. As part of his plea bargain agreement for his case of espionage against the Soviet Union, Robert Hanssen would be made to undergo a polygraph at any time as part of damage assessment. In Hanssen's 25-year career with the FBI, not once was he made to undergo a polygraph. He later said if he had been ordered; he may have thought twice about espionage.
Alternatively, the use of polygraph testing, where it causes desperation over dismissal for past dishonesty, may encourage spying. For example, Edward Lee Howard was dismissed from the CIA after during a polygraph screen, he truthfully answered a series of questions admitting to minor crimes such as petty theft and drug abuse. The CIA failed to see that the firing was an action that would logically anger Howard, and in retaliation for his perceived unjust punishment for minor offenses, he later sold his knowledge of CIA operations to the Soviet Union.
It is also worth noting that polygraph tests may not deter espionage. From 1945 to the present, at least six Americans had been committing espionage while they successfully passed polygraph tests. Two of the most notable cases of two men who created a false negative result with the polygraphs were Larry Wu-Tai Chin and Aldrich Ames.
In August 2008, the US Defense Intelligence Agency announced that it would subject each of its 5,700 prospective and current employees to a polygraph interrogation at least once annually.
A significant number of Federal appeals courts have upheld polygraph testing for Federal probationers as well. The most recent decision was by the Second Circuit Court of Appeals regarding a New York sex offender.
The UK will soon allow compulsory polygraph tests for convicted sex offenders released on license.
FOX has taken this one step further with their game show The Moment of Truth which pits people's honesty against their own sense of modesty, propriety, etc. Contestants are given a polygraph test administered by a polygraph expert in a pre-screening session answering over 50 questions. Later they must sit in front of a studio audience including their friends & family for the televised portion of the show. There they need only answer 21 answers truthfully "as determined by the polygraph" to win $500,000. The questions get more personal and/or more revealing as they advance. Most polygraph experts caution that the polygraph techniques used on Moment of Truth do not conform to any known or accepted methods of polygraphy.
Daytime talk shows, such as Maury Povich, frequently uses lie detectors in order to tell if someone is cheating on their significant other.
In the movie Ocean's 13, one of the characters beats a polygraph test by stepping on a tack when answering truthfully, which supposedly raises the polygraph's readings for the truthful answers so they equal to the deceptive ones.
In episode 109 of the popular science show Mythbusters, they attempted to fool the polygraph by using pain to try and increase the readings when answering truthfully (so the machine will supposedly interpret the truthful and non-truthful answers as the same.) They also attempted to fool the polygraph by thinking happy thoughts when lying and thinking stressful thoughts when telling the truth to try and confuse the machine. However, neither technique was successful and the examiner Michael Martin correctly identified each guilty and innocent subject. The show also noted the widely held opinion that, when done properly, polygraphs are correct 80-99% of the time.