A polygraph (popularly referred to as a lie detector) measures and records several physiological indices such as blood pressure, pulse, respiration, and skin conductivity while the subject is asked and answers a series of questions. The belief is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers. The polygraph was invented in 1921 by John Augustus Larson, a medical student at the University of California at Berkeley and a police officer of the Berkeley Police Department.
Many members of the scientific community consider polygraphy to be pseudoscience. Nonetheless, in some countries polygraphs are used as an interrogation tool with criminal suspects or candidates for sensitive public or private sector employment. US federal government agencies such as the FBI and the CIA and many police departments use polygraph examinations to interrogate suspects and screen new employees. Within the US federal government, a polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination.
Early devices for lie detection include an 1895 invention of Cesare Lombroso used to measure changes in blood pressure for police cases, a 1904 device by Vittorio Benussi used to measure breathing, and an abandoned project by American William Marston which used blood pressure to examine German prisoners of war (POWs). According to their son, Marston’s wife, Elizabeth Holloway Marston, was also involved in the development of the systolic blood pressure test: ‘Elizabeth suggested to him that ‘When she got mad or excited, her blood pressure seemed to climb.’ The comic book character, Wonder Woman, by William Marston (and influenced by Elizabeth) carries a magic lasso modelled upon the pneumograph (breathing monitor) test. Despite his predecessor’s contributions, Marston styled himself the ‘father of the polygraph.’ Marston remained the device’s primary advocate, lobbying for its use in the courts.
A device recording both blood pressure and galvanic skin response was invented in 1921 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. Several devices similar to Keeler’s polygraph version included the Berkeley Psychograph, a blood pressure-pulse-respiration recorder developed by C. D. Lee in 1936 and the Darrow Behavior Research Photopolygraph, which was developed and intended solely for behavior research experiments.
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 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 Chris?’), 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 Comparative Questions test (CQT). The CQT may be vulnerable to being 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
Polygraphy has little credibility among scientists. Critics maintain that rather than a ‘test,’ the method amounts to an inherently unstandardizable interrogation technique whose accuracy cannot be established. In the 1998 Supreme Court case, United States 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…’
‘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. 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.’
Summarizing the consensus in psychological research, professor David W. Martin, PhD, from North Carolina State University, states that people have tried to use the polygraph for measuring human emotions, but there is simply no royal road to (measuring) human emotions. Therefore, since one cannot reliably measure human emotions (especially when one has an interest in hiding his/her emotions), the idea of valid detection of truth or falsehood through measuring respiratory rate, blood volume, pulse rate and galvanic skin response is a mere pretense. Since psychologists cannot ascertain what emotions one has, polygraph professionals are not able to do that either.
Polygraphy has also been faulted for failing to trap known spies such as double-agent Aldrich Ames, who passed two polygraph tests while spying for the Soviet Union. The polygraph also failed to catch Gary Ridgway, the ‘Green River Killer.’ Ridgway passed a polygraph in 1984 and confessed almost 20 years later when confronted with DNA evidence.
Conversely, innocent people have been known to fail polygraph tests. In Wichita, Kansas in 1986, after failing two polygraph tests (one police administered, the other given by an expert that he had hired), Bill Wegerle had to live under a cloud of suspicion of murdering his wife Vicki Wegerle, even though he was neither arrested nor convicted of her death. 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.
Law enforcement agencies and intelligence agencies in the United States are by far the biggest users of polygraph technology. In the United States alone all federal law enforcement agencies either employ their own polygraph examiners or use the services of examiners employed in other agencies. This is despite persistent claims of unreliability. For example in 1978 Richard Helms, the 8th Director of Central Intelligence, stated that: ‘We discovered there were some Eastern Europeans who could defeat the polygraph at any time. Americans are not very good at it, because we are raised to tell the truth and when we lie it is easy to tell [we] are lying. But we find a lot of Europeans and Asiatics [who] can handle that polygraph without a blip, and you know they are lying and you have evidence that they are lying.’
Several countermeasures designed to pass polygraph tests have been described. 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.’
Other suggestions for 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.
In 2007, polygraph testimony was admitted by stipulation in 19 states, and was subject to the discretion of the trial judge in federal court. The use of polygraph in court testimony remains controversial, although it is used extensively in post-conviction supervision, particularly of sex offenders. In Daubert v. Merrell Dow Pharmaceuticals (1993), the old Frye standard was lifted and all forensic evidence, including polygraph, had to meet the new Daubert standard in which ‘underlying reasoning or methodology is scientifically valid and properly can be applied to the facts at issue.’ While polygraph tests are commonly used in police investigations in the US, no defendant or witness can be forced to undergo the test.
In the American military and intelligence communities, polygraphs have been administered both as terms of qualifying for a security clearance and as part of a periodic reinvestigation to retain a clearance. There is no uniform standard for whether the polygraph is needed, as some methods of adjudication do not demand a successful polygraph test to earn a clearance. Other agencies, particularly certain military units, actually prohibit polygraph testing on their members. According to a GPO report to congress, polygraphy in the security clearance context has little utility in detecting untruth, but significant utility in inducing verbal admissions. That is, polygraphy is mainly useful as a prop in the interrogation process. Further, this likely accounts for its continuing use by government agencies.
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.
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 when, during a polygraph screening, 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.
A hand-held lie detector is being deployed by the U.S. Department of Defense according to a report in 2008. The Preliminary Credibility Assessment Screening System, or PCASS, captures less physiological information than a polygraph, and uses an algorithm, not the judgment of a polygraph examiner, to render a decision whether it believes the person is being deceptive or not. The device will be used first in Afghanistan by U.S. Army troops. The Department of Defense ordered to limit its use to non-U.S. persons.
Sexual offenders are now routinely polygraphed in many states of the United States and it is often a mandatory condition of probation or parole. In Texas, a state appellate court has upheld the testing of sex offenders under community supervision and has also upheld written statements given by sex offenders if they have committed a further offense with new victims. These statements are then used when a motion is filed to revoke probation and the probationer may then be sentenced to prison for having violated his or her probation.
Regular polygraph testing is sometimes also used during the rehabilitation of convicted sex offenders. Questioning the offender specifically about their inner thoughts, desires, and impulses is intended to give a general indication of their treatment progress and likelihood of future offenses. Similarly, predatory or violent offenders at some facilities may also undergo testing for involuntary physical arousal when shown provocative images relating to their past crimes. Perhaps the most well-known example of this rehabilitation technique is practiced at Coalinga State Hospital in California.
Lie detection has a long history in mythology and fairy tales; the polygraph has allowed modern fiction to use a device more easily seen as scientific and plausible. Notable instances of polygraph usage include uses in crime and espionage themed television shows and some daytime television talk shows, cartoons and films. The most notable polygraph TV show is ‘Lie Detector,’ which first aired in the 1950s created and hosted by Ralph Andrews.
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