Michele Vittorio, University of New Haven

The use of polygraphs in detecting deception is controversial, and there is no consensus in the scientific community about the effectiveness of this technology in identifying deceptive individuals during criminal investigations and employment screenings. The purpose of this paper is to present and evaluate different studies that analyzed the benefits and the shortcomings of the current applications of polygraphs in the United States, and to produce a recommendation based on their conclusions. According to the evidence and research reviewed, it appears appropriate to exclude currently available polygraph testing procedures from pre-employment screening and background investigations in both private and government organizations, and to confirm the non-admissibility of polygraph examinations in criminal courts. Furthermore, it is recommended to develop further research in this field, to improve the consistency, reliability, and testability of the different types and applications of polygraphs in different settings and situations.

Are Polygraph Programs Effective?

This paper presents a review of the contemporary research on polygraph testing, to estimate its accuracy and potential as a screening and investigative tool, in supporting the work of law enforcement and other agencies in detecting deception. Polygraphs are utilized as one of the sources of information for security screening and as a supporting tool for criminal investigation. It is therefore important to understand if the resources dedicated to polygraph testing are justified by the results, and consider if the use of polygraphs is supported by evidence-based practice.

Other investigative methods could be employed to identify deception, such as face-to-face interrogations conducted by trained observers or traditional investigators. Studying the reliability of polygraphs requires an evaluation of the eventual marginal benefits that polygraphs can deliver in comparison with negative outcomes, such as false positive and false negative responses (National Research Council [NRC], 2003). According to recent estimates, approximately 2.5 million polygraphs test are conducted in the United States each year, and each test has an estimated cost of $700 (Alder, 2002; Harris, 2018). This raises concerns regarding the accountability of government organizations, resource allocation, protection of privacy, and the human rights of individuals who are tested (Rutbeck-Goldman, 2017). The Federal Bureau of Investigations, by itself, estimated a budget of $24.9 million to fund its polygraph program between 2002 and 2005 (U.S. Department of Justice [DOJ], 2006).

Polygraphs and Lie Detection

A polygraph is a device that collects and enables the analysis of human physiological responses through sensors physically connected to the individuals examined by this system. Polygraphs are employed to detect deception while the examinee answers a set of questions. They are utilized in different sectors, such as law enforcement agencies, the legal community to support forensic investigations, the private sector, and the U.S. federal government. In addition to criminal investigations, they are used to conduct pre-employment screenings.

The most common polygraph is the Comparative Question Test (CQT; Reid, 1947), which consists of monitoring the variations of physiological parameters, such as blood pressure, breathing, and dermal responses during an interview. CQT relies on two types of questions: those relevant to the purpose of the investigation and control questions, typically utilized as a baseline to evaluate and analyze physiological responses associated with lying. Deceptive subjects are expected to show more intense physiological responses in answering to the relevant questions, in comparison to responses elicited by the control questions.

CQT is a not a deterministic test that can identify deception, but rather a method to measure subjective physiological differences which could be linked to deception, by employing a probabilistic approach.  An alternative format of polygraph, less frequently used, is the Concealed Information Test (CIT; Vershuere et al., 2011). CIT is based on measuring the cognitive reaction of the examinees when relevant information is reported by the interviewer (Bradley, 2009). This technique involves recording physiological responses, such as respiration and electrodermal activity, allegedly associated to a reaction to significant stimulus, which could represent, for example, crime-related information.

The idea of monitoring systolic blood pressure as symptoms of deception in legal processes was introduced by Marston in 1915 and Marsden in 1921 (Alder, 2002; Synnott at al., 2015).  Larson and Keeler subsequently expanded the applications of the first polygraphs during the 1930s, by adding measures of breathing and skin conductance. The admission of polygraph tests results as evidence in court was rejected in Frye v. United Sates (1923), because the scientific support for the accuracy of the polygraph tests was not established. The further development of the polygraph in subsequent years included the introduction of the galvanic skin response (Synnott at al., 2015) and the CQT test (Reid, 1947).

By the beginning of the 1960s, U.S. federal agencies were conducting around 19,000 polygraph tests each year (Grubin & Madsen, 2005). Around this time, the US Congress considered the use of polygraphs to screen federal employees, but concluded there was not enough empirical evidence on the effectiveness of these devices and techniques in identifying deception. The National Security Decision 84 in 1983 allowed the use of polygraphs to test more than 22,000 government employees. However, this directive was rescinded rather quickly, after another review by the Office of Technology Assessment concluded that the screening capacity of polygraphs was not supported by empirical evidence, and that examinees could apply countermeasures to pass a polygraph test (Synnott et al., 2015). Subsequently, the Federal Employee Polygraph Protection Act was introduced in 1988, to regulate and limit the utilization of polygraphs in the private sector, while the Department of Defense expanded screening by employing this technology as a measure to deter spying (NRC, 2003). Finally, in a related case of Daubert v. Merrell Dow Pharmaceuticals (1993), it was held that scientific evidence could be accepted in courts even without meeting the requirement of general acceptance by the scientific community, which points to the existing body of evidence on the reliability and validity of polygraph testing.

Reliability and Validity of Polygraph Testing

According to Synnott (2015), the most commonly administered type of polygraph test is the CQT, followed by the CIT. CQT relies on measuring the physiological responses, such as increased movements and heart rate, induced by the stress that should be caused by deception (Ekman, 2009). A more recent development of CQT includes the employment of functional magnetic resonance imaging (fMRI), which measures blood flow in the brain, by assuming that deception could be correlated with an increased brain activity (Kozel et al., 2005).

CIT instead analyzes cognitive reactions of the individuals when relevant information (e.g., related to a criminal event) are mentioned (Bradley, 2009). CIT measures the physiological responses that could be interpreted as a reaction to significant verbal stimulus. While CQT aims to detect deception, CIT focuses on determining if the individuals tested recognize the information collected during the investigations as relevant. Concealed Information Tests (CIT) are not used frequently, with the exception of law enforcement agencies in Japan. They require a considerable effort before the test is conducted, to collect all the information necessary to formulate the questions, which are usually proposed in a multiple-choice format. The application of CIT in criminal investigations is based on the assumption that the examinee knows and can recall details related to a criminal event that are not publicly available, and therefore the questions should be focused on facts that can be remembered easily, such as the type of murder weapon (Yu et al., 2019).

Both tests are probabilistic and consist of three phases: a pretest interview, the data collection during the interview, and the data analysis post-interview (NRC, 2003). It is important to note how the evaluation of the reliability of CQT and CIT should take into account that the outcomes could be influenced not only by the type of test, but also by how each of the three phases are planned and conducted (Nelson, 2015).

Several reviews were conducted to determine the validity of CQT tests. Some studies claimed that the level of accuracy was consistently above 80% (Honts & Turber, 2019), while others indicated how the conclusions cannot be generalized, and utilizing polygraph in security screening and forensic lie detection cannot be scientifically justified (NRC, 2003; Iacono & Ben-Shakhar, 2019).  An exhaustive evaluation conducted by the NRC (2003) considered 37 laboratory studies and 7 field studies on the accuracy CQT and established a median rate of accuracy of 85% in detecting deception.  Honts and Thurber (2019) recently reviewed empirical studies on CQT, reporting an accuracy generally above 80%. This rate could be even higher when the results are interpreted by employing computerized algorithms (Raskin et al., 2019). 

Iacono and Ben-Shakhar (2019) highlighted how the accuracy rates should consider both the rate of deceiving individuals correctly identified, and also the rate of people correctly classified as truthful. They analyzed the data reported by the NRC (2013), concluding that to keep the rate of false positives below 10%, it would be necessary to reduce the accuracy rate in identifying deception to at least 73.8%. Vrij (2004) investigated the ability of police officers to detect lies in videotaped interrogations and reported an accuracy rate of 65%, while Bond and DePaulo (2006) indicated that regular people could achieve on average a rate of 54% correct in lie-truth classification. The accuracy of the CQT test could be, therefore, generally considered above or well above chance, and significantly higher in comparison with the general skills of criminal justice investigators and the general population.

It should be noted, however, that the empirical studies on polygraph tests were mostly conducted in laboratory environments and on individuals not trained in counter-measuring the readings of the polygraphs (NRC, 2003). Furthermore, the three phases of the CQT (pre-test interview, test, and analysis) generally are not standardized, and their variability makes an objective evaluation of the tests more difficult (Synnott et al., 2015). One fundamental assumption of the validity of CQT relies on the correlation between lying and emotional responses, but emotions, such as fear and strong feelings of affection, could alter the responses even when the examinee is not lying (Vrij, 2004).

One of the most relevant problems reported in the research on CQT concerns the high numbers of false positives (Iacono & Ben-Shakhar, 2019). As indicated by the NRC (2003), the number of spies and people who represent a threat to the national security are very low within the government organizations, and it is therefore necessary to possess a very accurate test to identify them. Furthermore, it could be argued that trained spies could employ techniques to counter the polygraph, making very challenging to detect the line between deceiving and truthful examinees. Consequently, there is an increased risk of classifying loyal employees as deceptive, making the reliability of pre-screening application of CQT not justifiable and generally not accepted by the scientific community (NRC, 2003; Iacono & Ben-Shakhar, 2019; Synnott et al., 2015). In contrast, Honts and Thurber (2019) noted how the accuracy of CQT is statistically very high and scientifically demonstrated, and therefore polygraphs could support the criminal justice system in improving the efficiency of investigations and reduce criminal justice problems, such as wrongful convictions.

However, CQT testing currently cannot be considered reliable by the scientific community. In a survey completed by members of the American Psychological Association, only one third of the sample stated that CQT tests are supported by scientific evidence, and one fourth of the members interviewed asserted that the results of CQT tests should be admitted in courts (Iacono & Likken, 1997). Despite these concerns, CQT is generally considered the most frequently used polygraph worldwide (Yu et al. 2019, Synnott et al., 2015), while the difficulties associated with the preparation of effective questions make the alternative polygraph method (the CIT) less utilized (Verschuere et al., 2011). The most recent implementation of CQT, using fMRI technology, was tested only in simulations conducted in laboratories. Despite an accuracy rate between 78% and 90%, empirical studies in real world conditions are necessary to estimate the usefulness of this technology in detecting deception (Spence, 2008). It also should be noted that the utilization of fMRI requires additional resources in terms of time, expertise, and equipment, making this technology significantly more expensive than traditional CQT, and ultimately, more unlikely to be employed in the near future (NRC, 2003).

CIT is based on a set of multiple choice questions concerning information that is known to the interviewers, and which allegedly should be known only by people involved in the event. During the preparation phase of a CIT, it is therefore important that some relevant information is available but not shared with the media and the public. CIT is conducted with the same equipment and following the same procedure of a CQT test, but requires a different preparation phase, in which the relevant information is collected and transposed in the questions.  The theoretical framework that supports CIT is the Orienting Response (OR) theory that explains how individuals tend to react quickly to a significant stimulus by, for example, increasing heart rate and modifying skin conductance. According to the OR, a guilty individual should react more intensively when exposed to known information connected to a criminal event (Synnott et al., 2015).

While CIT is used frequently in criminal investigations only in Japan (Yu at al., 2019), the scientific community is more supportive of CIT in comparison with CQT (Iacono & Likken, 1997).  However, the effectiveness of CIT has not been studied often in real world situations, but typically through simulations. Moreover, the accuracy of CIT reported in empirical research is variable, ranging from 50% to 90%. By contrast, with CQT, there is less evidence that individuals tested through CIT could employ countermeasures to alter the results (Ben Shakhar & Elaad, 2003).

Polygraph Applications and Problems

The federal Employee Polygraph Protection Act of 1988 prohibited the utilization of polygraphs in private employment, but excluded potential and current government employees, as well as every individual who could handle information relevant to national security. The DOJ (2006) reported an average of more than 12,000 tests conducted each year by the Federal Bureau of Investigation (FBI), Drug Enforcement Administration (DEA), the Office of the Inspector General (OIG), and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), to support, for example, pre-employment screenings and criminal investigations. It was estimated that government agencies could test approximately 70,000 persons each year for clearance and employment purposes (Taylor & Watson, 2013). By contrast, the results of polygraph testing are generally not admitted in judicial courts, due to the potentially prejudicial nature of opinion testimony of polygraph examiners and the low level reliability of polygraph examinations (Saxe & Ben-Shakhar, 1999). This was most recently confirmed by the US Supreme Court, which rejected polygraph evidence based on the lack of scientific consensus on its reliability (U.S. v. Scheffer, 1998). 

Contemporary research on polygraph tests suggests they significantly improve the chance to detect deception (NRC, 2013; Honts & Thurber, 2019), but several shortcomings make the application of this technology inefficient and unreliable (Iacono & Ben-Shakhar, 2019; NRC, 2003; Synnott et al., 2015). The problems most frequently reported concerning polygraph testing can be summarized in the following points:

• Countermeasures can reduce the rate of deceptive individuals correctly identified (NRC, 2003).
• The identification of a small number of deception yields a high rate of false negative outcomes, making current polygraph testing not viable. According to Rutbeck-Goldman (2017), for example, 400,000 truthful employees face the negative consequences of being misclassified as deceptive each year.
• The lack of consistency of polygraph testing procedures in real case scenarios makes the evaluation of the outcomes difficult and not reliable (Synnott et al., 2015; DOJ, 2006).
• Most of the evidence supporting the use of polygraphs is developed by using laboratory experiments rather than real word studies (NRC, 2003; Iacono & Ben-Shakhar, 2019).

Further important factors corroborate the hypothesis that polygraph technologies are not effective lie-detection methods. Organizations that utilize polygraphs could rely excessively on this testing procedure and neglect some other more traditional methods, such as traditional prescreening investigations, by reducing the likelihood of identifying deceptive individuals (NRC, 2003). Furthermore, concerns in the area of civil rights were raised in relationship with polygraph testing. One of the main issues pertains to the possibility that past actions, possibly unrelated to the job functions, could be utilized to deny a job opportunity or sanction a current employee. Polygraphs also were linked to possible discriminatory effects on minority groups. Some evidence confirmed that the physiological responses of individuals feeling stigmatized during a CQT are more intense and therefore more likely to yield a negative result. It also could be argued that the lack of standardized procedures could increase subjective evaluation and, eventually, racial bias (NRC, 2003; Rutbeck-Goldman, 2017).

Policy Options and Recommendations

Following the evidence presented in this document, three possible general directions could be taken to regulate polygraph testing:

1. Expand the application of the Federal Employee Polygraph Protection Act to include current and prospective employees of the government organizations.

This option is based on lack of consensus in the scientific community regarding the reliability of polygraph testing, confirmed by several studies reported in this document, the US Supreme Court, and the Federal Employee Polygraph Protection Act itself. The benefits of this line of action could include, for example, a consistent reduction of economic resources that could be reinvested in conducting investigations, interviews, background checks, and research on technological systems to detect deception.

It should be noted that this course of action likely will lead to a reduction of interest and resources dedicated to polygraphs, undermining the development of promising technologies that could significantly identify and classify deception. Another possible negative consequence could be related to the risk of stigmatizing the whole polygraph technology as not being useful or reliable, missing the opportunity of researching the eventual benefits of standardized procedures and the application of methods as CIT in the criminal investigations. This showed promising results in other countries, such as Japan (Yu et al., 2019).

2. Limit the application of polygraph testing to specific cases to support the conclusion of pre-existing investigations.

Under this option, polygraphs should be used only on individuals who, after a background check or investigative, already are suspected of hiding relevant information or reporting untruthful information. This approach will significantly reduce the resources dedicated to polygraph testing and the numbers of tests and examiners. By following this option, fewer examiners could benefit from more resources for professional training and the development of standard procedures, possibly making the tests and their evaluations more consistent and reliable. The rate of false positives should be reduced by the prescreening conducted through investigations and background checks, and the results of the polygraph tests could support or refute the information collected.

While this approach likely will reduce the number of tests performed and the resources employed, it should be stressed that the current technology seems to be not empirically supported, and therefore the results of the tests may not significantly improve quality and the quantity of the information gathered before the polygraph interview. It is possible that more consistent testing procedures and examiner skills will improve the reliability of the tests, but to reach this result, it would be necessary to reinvest economic and human resources in developing and testing new standards and best practices. It also should be noted that a decreased utilization of polygraphs could reduce the resources dedicated to polygraph programs, thereby making these goals not achievable in a short period.

3. Continue to use polygraphs according to the current policies.

Federal Courts and private sectors exclude evidence collected by polygraphs already, and government organizations are employing polygraphs because it seems to provide the best technological support available in detecting deception. As noted in this document, polygraphs perform significantly better than human beings in classifying untruthful statements, and any support that could be utilized to protect the national security should be utilized to reduce the risks of potential important negative consequences.

However, examinees could successfully employ countermeasures to increase their likelihood of passing a polygraph test, independently from the truthfulness of their answers (NRC, 2003; Synnott et al., 2015; Iacono & Ben-Shakhar, 2019). Professional spies, for example, could be arguably aware of these techniques, making it very difficult for a polygraph examiner to identify very few untruthful individuals within a large truthful population, leading to an increased risk of false positives results (Rutbeck-Goldman, 2017).

Conclusion

The three general options described above highlight the factors that should be taken into account to define a policy that utilizes effectively the currently available polygraph technologies. However, it is also evident that most of the studies reported concurred in considering current polygraph testing procedures not scientifically reliable. The widespread utilization of prescreening polygraph testing, in particular through CQT, is therefore not justifiable.

Accordingly, it is advisable to expand the application of the Federal Employee Polygraph Protection Act to include current and potential employees of government organizations and their contractors, and exclude polygraph testing from the prescreening and investigating procedures. Furthermore, it is suggested to divert part of the resources currently dedicated to polygraph programs to study the reliability of CIT in criminal investigations and define standard methods that could improve the consistency of polygraph tests and their evaluation. Currently, it seems that pre-employment background checks and traditional investigations could provide more reliable information than polygraph testing, by limiting some of the possible shortcomings involved in utilizing polygraphs, such as the difficulties in estimating the accuracy rate, a measureable amount of false positives, and issues in the area of human rights. It is worth noting that the present recommendations are based on the technology and the information currently available and do not exclude that further developments in this area could make polygraphs more reliable and applicable in both employment and criminal investigations settings.

References

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Alder provides an historical review of the polygraph technique in the United States, by trying to explain the cultural and economic motivations behind the proliferation of lie-detection tests.

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The article proposed a description and a review of the two main polygraph testing methods: the Comparative Question Test (CQT) and the Concealed Information Test (CIT). The authors focused on analyzing the shortcomings and the potential of these two methods and concluded by underlining how the CIT seems to be a more promising investigative tool, by comparison with CQT.

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