Polygraph analysis

DEFINITION: interrogation technique that measures physiological responses to detect deception.

SIGNIFICANCE: Polygraph analysis, also known as lie detection, is widely used as part of law-enforcement investigations in the United States, although controversy exists regarding the reliability of the technique.

Polygraph analysis enjoys a rich history in the United States, where law-enforcement agencies have used it in interrogations with varying results since the early twentieth century. The reliability of the technique for detecting deception is the topic of ongoing controversy. Some proponents claim that analysis can detect deception with approximately 95 percent accuracy, whereas many scientists contend that the technique detects deception at rates only slightly better than chance.

History

William Moulton Marston is credited with inventing the discontinuous polygraph, which records physiological signals only at select times during an interrogation. As an inventor and marketer, Marston brought great attention to the polygraph in the early twentieth century. He claimed that the polygraph was the end-all solution to difficulties with detecting deception during interrogation. Building on Marston’s invention, John A. Larson developed a continuous polygraph, which he called a cardio-pneumo-psychograph, in 1921. Unlike Marston, however, Larson was critical of the polygraph and cautioned against its use in court proceedings. Mirroring Larson’s viewpoint, the US Supreme Court decided in Frye v. United States in 1923 that insufficient scientific support existed to allow polygraph results to be used as evidence in court proceedings.

In response to the Frye ruling, scientists worked toward developing scientifically validated polygraphy techniques. In 1930, Leonarde Keeler, an associate of Larson, and John E. Reid helped form the Scientific Crime Detection Laboratory of Northwestern University to enhance polygraph interrogation methods. Keeler later opened the first polygraphy training school in 1938. Reid followed suit, opening John E. Reid and Associates in 1947. These two schools became the most prominent polygraphy schools in the United States.

Equipment

The equipment used during a modern polygraph interrogation includes a physiological data acquisition device that measures respiration, blood pressure, pulse, and palmar sweating on a continuous basis. The traditional polygraph is a mechanical instrument that records physiological signals on a moving paper chart. Following the interrogation, the chart is hand-scored by the polygrapher.

Increasingly, the traditional polygraph is being replaced by the computerized polygraph, which acquires, stores, and analyzes data in digital form. Computerized polygraphs often score charts by applying mathematical formulas based on the results of previous polygraph examinations.

Interrogation Techniques

Although most polygraphs measure the same physiological indicators, the interrogation techniques used by polygraphers vary greatly. The three most commonly used methods of interrogation are the irrelevant/relevant (I/R) test, the control question test (CQT), and the guilty knowledge test (GKT).

The I/R test was the original method of interrogation in early polygraphy, and it is still commonly used by some employers during personnel screening interviews. This technique uses a combination of task-irrelevant and task-relevant questions. An example of a task-relevant question is “Have you ever stolen an item valued at more than twenty dollars?” An example of a task-irrelevant question is “Is your name Bob?” The underlying rationale is that more marked physiological responses during task-relevant questions suggest deception. For instance, if an interview subject who was asked the two preceding questions had stolen an item valued at more than twenty dollars, that person would presumably show a greater physiological response to the relevant question than to the irrelevant question.

The CQT, which is a variant of the I/R test, is the most commonly used polygraphic technique in the United States. The CQT uses a combination of control, task-relevant, and task-irrelevant questions. An example of a control question is “Have you ever stolen an item valued at more than two dollars?” An example of a task-relevant question is “Did you steal one hundred dollars from Joe’s wallet on December 17?” Control questions are designed to elicit known lies from just about everyone, thereby serving as a baseline with which to gauge the examinee’s physiological “lie” response. The rationale is that guilty examinees should react more to task-relevant questions than to control questions because they are concerned about being caught for the specific crime in question, whereas examinees who are innocent of the crime in question will respond more to control questions because they are concerned about appearing to be criminal types.

The GKT technique investigates criminal guilt without attempting to identify a lying response. In this respect, it contrasts sharply with the I/R test and CQT. Although the GKT is rarely used by law-enforcement agencies in the United States, it is the preferred interrogation method in Japan. Instead of asking directly whether an examinee participated in a crime, the GKT attempts to assess concealed knowledge. It does so by asking specific questions about the crime, followed by multiple-choice options. For example, if the walls of the room in which someone was beaten were painted blue, a GKT question might be, “The paint in the room where the beating took place was: red, white, blue, or green?” The assumption is that guilty examinees will react more strongly to the details of a crime, whereas innocent examinees will not.

Applications

Until the late 1980s, many American businesses used polygraphy as a tool for screening employees and job applicants, but with the passage of the Employee Polygraph Protection Act of 1988, a federal law, private employers were prevented from using polygraphy in this way. Government agencies, contractors working with government agencies, and private-sector employees suspected of theft were exempted from this protection, however. Several government agencies, including the Federal Bureau of Investigation (FBI), the Central Intelligence Agency (CIA), the Department of Energy, and the National Security Agency, use the polygraph for employee screening on a regular basis.

Following the US Supreme Court’s decision in Frye v. United States, polygraph results were rarely introduced as evidence during court proceedings. In 1993, the Court’s ruling in Daubert v. Merrell Dow Pharmaceuticals built on the Frye ruling by developing guidelines for introducing scientific evidence into court proceedings. The guidelines the Court established, collectively known as the Daubert standard, are as follows: Scientific evidence must be based on a testable theory or technique; the theory or technique must be peer-reviewed; the technique must have a known error rate; and the underlying science must be generally accepted by the scientific community. Following the Daubert decision, polygraph evidence became largely inadmissible in criminal proceedings. In half of US state courts, polygraph evidence continues to be admissible in criminal proceedings when the defense and prosecution agree to the admissibility of the results before the test is taken. The results of polygraph analysis are commonly used in civil proceedings, however, and law-enforcement agencies often use the technique in screening criminal suspects.

Continuing Controversy

In 1997, David T. Lykken and William G. Iacono polled 363 scientists from the American Psychological Association and the Society for Psychophysiological Research concerning the use of GKT and CQT polygraph interrogation techniques. They found that although 75 percent of the scientists surveyed believed that the GKT was based on sound scientific evidence, only 33 percent held this view of the CQT. Moreover, only about 25 percent of the scientists polled believed that polygraph evidence should be allowed in a courtroom.

Critics of polygraph analysis assert that the technique rests on the faulty assumption of a “Pinocchio response”—that is, a specific physiological lie response or “signature” of deception. Scientific studies have found no evidence of such a response. Moreover, real-world studies of people who have been conclusively found guilty or innocent of crimes suggest that the polygraph has a high false positive rate, meaning that it mistakenly classifies many innocent people as guilty. These findings have led many critics, such as Lykken and Paul Ekman, to refer to the polygraph as an “arousal detector” rather than a lie detector. They assert that many people may fail polygraph tests not because they are guilty of crimes but because they display nervousness, indignation, or surprise in response to the relevant questions.

Polygraph analysis may also be plagued by false negatives or guilty individuals mistakenly classified as innocent. Some false negative results can be produced by “countermeasures”—tricks that help people “beat” the polygraph by allowing them to boost their physiological responses to irrelevant or control questions. Such countermeasures can be physical (such as biting down on one’s tongue during these questions) or mental (such as performing complex mental arithmetic during these questions).

Attempts to study the validity of polygraph results are complicated by at least two major obstacles. First, laboratory studies cannot simulate the intense pressure of real-world polygraph interrogations because the arousal associated with a lie generated for the purposes of a study probably differs from that associated with a lie generated to avoid imprisonment or even capital punishment. Second, studies of polygraph use in real-world settings may overestimate the accuracy of the results as applied to the general population because many suspects are guilty of the crimes of which they have been accused. For example, if thirty-six of the forty suspects in a study sample are guilty and all forty polygraph tests indicate guilt, one could claim that the polygraph was 90 percent accurate. These obstacles suggest that novel research methodologies are required to evaluate the validity of polygraphy in practice.

Bibliography

Cook, Glen and Charles Mitschow. "Beyond the Polygraph: Deception Detection and the Autonomic Nervous System." Federal Practitioner, vol. 36, no. 7, July 2019, www.ncbi.nlm.nih.gov/pmc/articles/PMC6654171. Accessed 19 Aug. 2024.

Honts, Charles R., et al. "A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test." Applied Cognitive Psychology, vol. 35, no. 2, 18 Dec. 2020, doi.org/10.1002/acp.3779. Accessed 19 Aug. 2024.

Iacono, William G., and David T. Lykken. “The Validity of the Lie Detector: Two Surveys of Scientific Opinion.” Journal of Applied Psychology, 82 (1997): 426-433.

Iacono, William G., and Christopher J. Patrick. “Polygraph (’Lie Detector’) Testing: Current Status and Emerging Trends.” In The Handbook of forensic Psychology, edited by Irving B. Weiner and Allen K. Hess. 3d ed. Hoboken, N.J.: John Wiley & Sons, 2006.

Inbau, Fred E., John E. Reid, Joseph P. Buckley, and Brian C. Jayne. Criminal Interrogation and Confessions. 4th ed. Boston: Jones & Bartlett, 2004.

Larson, John A. Lying and Its Detection: A Study of Deception and Deception Tests. Chicago: University of Chicago Press, 1932.

Lykken, David T. A Tremor in the Blood: Uses and Abuses of the Lie Detector. 2d ed. New York: McGraw-Hill, 1996.

Marston, William Moulton. The Lie Detector Test. New York: Richard R. Smith, 1938.

National Research Council. The Polygraph and Lie Detection. Washington, D.C.: National Academies Press, 2003.

Raskin, David C., and Charles R. Honts. “The Comparison Question Test.” In Handbook of Polygraph Testing, edited by Murray Kleiner. San Diego, Calif.: Academic Press, 2002.