The use of polygraphs in criminal investigations and as an evidential basis in court has been a common practice for many years. This psychophysiological measure is used as an aid to lie detection or supplement testimony for credibility determination of a defendant’s statement or introduce a plea bargain during the negotiation process between the prosecutor and the defense. However, in recent years, the validity of polygraphs has been controversial. Consequently, the admissibility of polygraphs remains a question of uncertainty. One of the crucial factors for polygraph admissibility is contested because of examinee deception and manipulation susceptibility. Even though it is vulnerable to deception, it is unable to detect deception. Polygraph was first invented in 1921, and just after two years, it was first used in a District of Columbia Circuit case, Frye v United States. Polygraph’s admissibility depends mainly on two crucial factors-both parties need to agree for its use in the case in some states and the state’s judicial acquiescence (Frye v. United States, 1923). In California, Arizona, Nevada, Georgia, and Florida, a polygraph can be used upon both party approval. Even though polygraph’s prominent use in court for one’s testimony determination technique throughout history, it still remains inadmissible in certain states. Why are polygraph results less admissible in court in recent years? Polygraph results are generally inadmissible in these state standards because of their scientific unreality based on various factors such as the examinee’s medical conditions, the examinee’s deception knowledge, the machine used, and the examiner.
What is a polygraph?
Human beings have relied upon the pre-frontal cortex of the brain for their executive functioning in decision-making. One of the crucial roles of the pre-frontal cortex is thought-processing, which is why, in deception, the pre-frontal cortex of the brain is also the most activated and utilized. As long as human beings have lived in a complex socialized environment, humans have used their executive functioning to deceive or detect deception for personal benefits or characterizing validation. For the longest in history, people have tried to develop techniques for detecting deception and finding truth. In the 20th century, with the development of modern science, lie detection was introduced as psychophysiological detection of deception with polygraph testing. The polygraph measures physiological arousal factors such as heart rate, blood pressure, respiration, perspiration, and skin conductance (National Research Council, 2003). The test includes a series of yes/no questions for the examinee while connected to the polygraph, which records the examinee’s physiological data transmitted by the set of sensors while answering the questions (National Research Council, 2003). This data is recorded analogically or digitally onto the polygraph machine called the polygraph chart. An additional test performed before the testing is called the pretest interview (National Research Council, 2003). The purpose of the pretest interview is to examine the examinee’s emotional state of the examinee and share the polygraph reading expectations by recording the physiological responses to general questions such as personal information. These question sets are designed to create a truth baseline of the examinee’s physiological responses to general questions to which the examiner already knows the answers (National Research Council, 2003). In the pretest interview, the examiner can inform the examinee that the polygraph can detect deception by demonstrating an example when the examinee is asked to lie about an unimportant matter and establishing the physiological differences between the truth baseline and the lie. This process helps the examiner to determine any deception during the polygraph testing by comparing the physiological differences when each question is answered.
Empirical research 1 — Frye v. United States
The polygraph was first used in the United States Court of Appeals for the District of Columbia in the Frye v. United States case in 1923. The case revolved around the admissibility of scientific evidence in determining deception. In this case, the crucial factor in determining the validity of testimonies was the systolic blood pressure analysis to be recognized by experts of the scientific world to be admissible in court (Frye v. United States, 1923). The defendant, in this case, was convicted of second-degree murder and appealed the verdict. The defense argued that the court should consider the use of a polygraph to determine the truthiness and validity of the defendant’s testimony (Frye v. United States, 1923). They added that the truthful statement is more spontaneous without much brain activity or effort, whereas lies require conscious effort and the brain’s executing function, resulting in increased blood pressure. Therefore, increase in blood pressure readings in the polygraph chart can be analyzed to determine the validity of the defendant’s testimony in deciding the verdict (Frye v. United States, 1923). The defense even offered to have the defendant’s polygraph analysis done in front of the jury. The court observed the polygraph test upon appeal; however, the court denied the request for a polygraph evidential basis due to a lack of scientific consensus.
Empirical research 2 — The Congressional Office of Technology Assessment (OTA)
The polygraph use was deemed inadmissible because of being vulnerable to deceptive measures. According to a technical memorandum by the Office of Technology Assessment of the United States Congress presented no scientific evidence on the validity of polygraph testing (OTA, 1983). In 1965 and in 1976, the House Government Operations Committee also concluded that there was no substantial evidence to establish the polygraph’s validity. They presented two major reasons affecting the validity of the polygraph. First, the polygraph test is a complex process that goes beyond just the examinee’s arousal factors. The types of individuals tested, the training of the examiner, the purpose of the test, and the types of questions asked, among many other factors, can differ substantially and affect the readings. The polygraph analysis is dependent on an examinee’s physiological responses to various questions and is therefore susceptible to deceptive techniques by the examinee. Secondly, in addition to the polygraph’s validity reliance on its results, it is also affected by the quality of research design and methodology (OTA, 1983). In a criminal investigation, if the polygraph is used, it would be after a suspect is identified-which provides the suspect prior knowledge and preparation for countermeasures or false positives. The false positive or countermeasures can include physical movement or pressure during the testing, drugs, hypnosis, biofeedback, and prior polygraph experience in passing (OTA, 1983). There are also mathematical chances of false positive deception identification (incorrect identification of innocent as deceptive) in polygraph testing when used for screening purposes. It is because, in screening situations, the group screened for guilt is usually small; there may be situations where a person in a sample group tested may have engaged in an unauthorized activity irrelevant to the case and feel susceptible to lying for specific questions to prevent self-incrimination of wrongdoing. These participants may show similar blood pressure discrepancies and have chances of being incorrectly identified (false positive) (OTA, 1983). The digital version of the polygraph or Computerized Polygraph System (CPS) faces similar countermeasure challenges. The reset version of the CPS algorithm uses three features-skin conductance amplitude, the amplitude of increases in the baseline of the cardiograph, and a line length composite measure of thoracic and abdominal respiration excursion (National Research Council, 2003). Even though the CPS methods of computational standard error are significantly smaller than the analog polygraphs, they face similar deceptive countermeasures. Since it is dependent on the data of the examinee’s physiological data baseline and analysis of physiological fluctuations against it, an examinee can deliberately increase blood pressure by thinking of adverse memories to create a higher baseline through biofeedback, so when the following question to physiological data is analyzed against the base, the discrepancy would be negligible. The CPS also faces various statistical and methodological challenges-using a magnitude of reference features or variables overfit the data and using less underfits the data (National Research Council, 2003).
Empirical research 3 — Laboratory study on GKT and GAT
Another crucial challenge the polygraph faces is the differentiation between the Guilty Knowledge Test (GKT) and the Guilty Actions Test (GAT). Guilty Knowledge Test (GKT) in a polygraph method is the test to infer the examinee’s knowledge of a crime, whereas Guilty Action Test is a method to infer the examinee’s concealed memory of committing the crime. However, even though the polygraph might be able to identify a participant on the Guilty Knowledge Test or the Guilty Action Test, the polygraph is unable to differentiate the participant who is knowledgeable of the crime from the person who has committed the crime. In a laboratory study, the effects of information and deception on different levels of Guilty Knowledge Tests were examined. Participants included 120 men taking an introductory psychology class were presented with a mock crime in which participants had taken the role of committing or witnessing the crime (Bradley et al., 1992). They were instructed to answer “no” to repeated GAT or GKT questions or remain silent. A monetary reward was awarded to participants appearing innocent on the test. The skin resistance response data associated with each participant’s answers were recorded on the polygraph. The findings showed that innocent witnesses tested on the Guilty Knowledge Test (GKT) and guilty participants tested on both the Guilty Knowledge Test (GKT) and Guilty Actions Test (GAT) presented guilty results without any distinctions between the two groups. Therefore, if innocent informed suspects exist in substantial amounts in testimonial analysis, then the Guilty Knowledge Test (GKT) is most likely to misclassify innocent informed suspects as guilty (Bradley et al., 1992). This misclassify is extremely grievous in a criminal investigation when people’s lives are on the line.
Empirical research 4 — Laboratory study on CQT
Another methodological challenge that the polygraph faces among the distinctions between the Guilty Knowledge Test (GKT) and Guilty Actions Test (GAT) is the Control Question Technique (CQT). The polygraph consists of 3 types of yes/no questions: 1. Relevant questions-these pertain directly to the crime or subject of investigation, 2. Control questions-they are not related to the crime but designed to be arousing and ego-threatening questions, and 3. Irrelevant questions-neutral questions generally presented at the beginning of the polygraph testing to set a baseline for participants’ physiological response data (Bradley et al., 1992). The polygraph then uses all three types of questions to recognize the participant’s physiological discrepancies to determine deception. However, the underlying inefficient factor of the Control Question Technique (CQT) is that it depends on the participant’s emotional state contrasting with relevant questions in determining deception. i.e., if a suspect tends to react more to relevant questions is classified as guilty, whereas a suspect who tends to reach more to control questions is classified as non-deceptive (Bradley et al., 1992). It is true that deception is often associated with some fear or anxiety, but polygraph testing and the interrogative environment can have similar emotional effects. Because of the polygraph’s scientific inadequacy, it still generally remains inadmissible.
Empirical research 5 –Deception Detection and the Autonomic Nervous System
Throughout history, humans have been interested in developing lie detection techniques using physiological arousal. Even in ancient times, it was believed that lying had physiological effects; in ancient Israel, if a woman was accused of adultery, she would be considered guilty if she developed a swallow abdomen after drinking “water of bitterness” (Book of Numbers [Number 5:11–31]). In ancient China, those accused of deception would be forced to hold dry rice in their mouth and considered guilty if the expectorated rice was dry (Cook & Mitschow, 2019). These ancient lie detection techniques revolved around the idea of physiological effects; epinephrine, also known as adrenaline, is secreted during times of stress and causes relaxation of smooth muscles, leading to reduced bowel movement and dry mouth (Cook & Mitschow, 2019). Even though most ancient methods of lie detection before the modern era were based more on superstition rather than scientific reasoning of a physiological premise, similar physiological discrepancies are observed in modern-day polygraphs in relation to deception-induced stress. Therefore, using vital signs as an indirect measurement of deception-induced stress makes the polygraph vulnerable to a false positive or negative result if the participant has a medical or acquired condition that affects the autonomic nervous system (ANS) (Cook & Mitschow, 2019). The use of alcohol or neurotransmission-altering drugs can affect the ANS. Regardless of multiple evidential research on the inefficacy of polygraphs, it is still used in many governmental and law enforcement agencies to aid in security screening and negotiations. The United States Department of Defense (DoD) and other law enforcement and governmental agencies also use the polygraph as a step of the pre-employment screening. The United States Department of Defense (DoD) and other law enforcement agencies use the polygraph in multiple interrogations and screenings. DoD Directive 5210.48 and Instruction 5210.91 enable DoD investigative organizations such as the Naval Criminal Investigative Service, the National Security Agency, United States Army Investigational Command to use polygraphs during investigations of suspected involvement with foreign intelligence, terrorism against the United States, mishandling of classified documents, and other serious violations (Cook & Mitschow, 2019). Therefore, the efficiency of the polygraph in these circumstances would only stand valid on the participant’s prior polygraph knowledge of countermeasure techniques.
Conclusion
Multiple studies on human being’s ability to detect truth or deception have shown human failure. When asked to recognize the truth from falsehood, people correctly recognized lies as false only 47% of the time and truth as non-deceptive 61% of the time. It is evident that we are poor lie detectors, which is why, throughout history, there has been a substantial interest in the development of lie detection technologies. The ability of deception detection is an important factor in the adjudication of legal processing, security risk management, and validating authenticity. However, the polygraph, in its current technological state, is vulnerable to deceptive countermeasures, misclassification, and methodological discrepancies. It makes the polygraph inadmissible and an inefficient tool for investigative purposes, especially when a person’s life is in jeopardy.
References
Scientific Validity of Polygraph Testing: A Research Review and Evaluation — A Technical Memorandum (Washington, D. C.: U.S. Congress, Office of Technology Assessment, OTA-TM-H-15, November 1983).
Cook, L. G., & Mitschow, L. C. (2019). Beyond the Polygraph: Deception Detection and the Autonomic Nervous System. Federal practitioner: for the health care professionals of the VA, DoD, and PHS, 36(7), 316–321.
Bradley, M. T., McLaren, V., & Carle, S. B. (1992). Deception and Non-Deception in Guilty Knowledge and Guilty Actions Polygraph Tests. https://doi.org/10.21236/ada303184
National Research Council. 2003. The Polygraph and Lie Detection. Washington, DC: The National Academies Press. https://doi.org/10.17226/10420.
Ben‐Shakhar, G., Bar‐Hillel, M., & Lieblich, I. (1986). Trial by polygraph: Scientific and juridical issues in lie detection. Behavioral Sciences & the Law, 4(4), 459–479. https://doi.org/10.1002/bsl.2370040408
Frye v. United States, 293 F. 1013 (D.C. Cir. 1923)
