The Validity of Polygraph Testing: The Consequences and Future of Using Lie Detectors in Criminal Cases
By Katrina Azar’27
In 1988, Frank Sterling failed a polygraph test. As a result, he was wrongfully incarcerated for 22 years. (1) Mark Christie, the individual actually guilty for the crime, passed the same polygraph test. He then went on to abduct and kill a four-year-old. (2) How is it that a test that may provide false evidence carries such weight in criminal cases?
The polygraph test measures involuntary functions in order to determine if one is truthfully answering questions. Blood pressure, heart rate, perspiration, and respiration are all measured; when results show signs of nervousness, anxiety, and stress, officials may assume that the participant is hiding something or even lying. (3) However, natural physiological reactions are taken into account as a source of error. To increase the accuracy of the test, participants are given a set of control questions where polygraph examiners differentiate between how they react to truthful statements versus false claims.
Historically, various techniques have been employed in an attempt to discern deceptive statements from truthful ones, and the development of lie detection methods remains an active area of research.
In ancient China, suspects were forced to chew grains of rice in order to check for innocence. It was thought that the guilty would spit out drier, unstuck rice, as nervousness was often characterized by a dry mouth. (4) Italian criminologist Cesare Lomborso theorized that if you put a liar’s hand in a jar of water, their hand would swell due to rising blood pressure, and water would overflow from the jar. In 1921, the first polygraph test was produced by John A. Larson; it incorporated the works of many psychologists and researchers to develop a way to “detect deception.” (5) The first significant use of polygraph testing in the legal field was in 1923, in United States v. Frye. (6) However, the court rejected the evidence for multiple reasons. Not only was the idea of a polygraph test not commonly accepted by the public, but many also rejected the science around it. The idea of determining the admissibility of scientific evidence in court became known as the Frye Standard. (7) The Frye Standard served as a gateway to a new method of utilizing physiological evidence, which then became widely accepted. Not only was this method incorporated in court, but it also assured caution when approaching new forms of evidence. (8)
Today, the rules of polygraph test use differ. As a result, tests are generally not admissible in court unless both parties agree to their use. (9) Although online sources such as fictional dramas and social media make it appear as if the results of polygraph tests are accurate, this is not the case; in fact, several states have their own rules regarding polygraph testing. 31 states do not allow any form of polygraph testing, while 19 states do. (10) It is acknowledged that several external factors—including anxiety, stress, and the like—may alter the accuracy of the test. Furthermore, while rare, people may train for an extended period in order to suppress their emotions and the corresponding physiological responses, leading to a false passing result on the test. With many sources of error regarding polygraph testing, it is understandable that restrictions would be placed on their usage in criminal court cases, such as that of United States v. Frye. (11)
A few months after Sterling failed his polygraph test and was imprisoned, the “Angel of Death,” Charles Cullen, also escaped murder accusations. (12) Cullen was a nurse who murdered approximately 40 people via lethal injections. After passing a polygraph test, Cullen went on to murder another 39 people. Eventually, he was convicted, but the effects of relying on a polygraph test to determine his innocence cost many their lives. (13)
Even though there are many situations where the polygraph test delayed the time it took to ensure justice, there are still many situations where the polygraph test served as a key lead in cases. In September 2009, at the age of 24, Yale graduate student Annie Le was murdered just before her wedding. Police identified Raymond Clark III, her research assistant, as a viable suspect after he failed a polygraph test. The 26-year-old’s failure to pass the exam encouraged police to investigate Clark’s role in the crime at a deeper level. Eventually, he was convicted.
The American Polygraph Association claims that lie detector tests are "highly accurate" with an accuracy rate above 90 percent when administered correctly. However, critics argue that these tests have an accuracy rate of only about 70 percent. (!4) Despite their imperfect accuracy, it seems that polygraph tests are still more likely than not to be an accurate measure of determining suspects. Considering these statistics and varying rules on the use of polygraph tests per state, there are many possibilities for the future of polygraph tests in court.
Given the unreliability of polygraph testing and the numerous ways in which results can be manipulated, current laws governing its use in court appear to be a justified response to such a precarious piece of technology. However, despite the requirement for both parties to consent to the use of test results in court, there are other ways to take advantage of the polygraph test. Certain situations may call for one party to independently take advantage of the polygraph test to find possible leads (such as in the case of Annie Le and Raymond Clark III). Furthermore, as time passes, methods of lie detection are gaining accuracy, potentially leading to revisions of laws regarding criminal cases and the admissibility of evidence. It is possible that in the future, both parties will not have to consent in order to allow lie detector results in a criminal case; this may be able to provide the court with crucial information. Although the polygraph test is not yet reliable enough to be the breaking point between an innocent and guilty verdict, there may be some validity to its results.
As lie detection has developed from chewing rice to polygraph testing, a new form of lie detection is currently being developed. EyeDetect, an eye tracker that is seemingly more efficient and accurate than a polygraph test, records eye movements while suspects answer a series of true/false questions. These behaviors are analyzed, and the suspect is categorized as either “truthful or deceptive.” The rate of accuracy appears to be between 86 and 88 percent. One difference between this and polygraph testing is that the capacity to exploit the test and retrieve false results is significantly less due to EyeDetect measuring extremely involuntary changes such as pupil size that directly reflect brain activity.
Regardless of these technological advancements, lie detectors like polygraph testing and EyeDetect still cannot perfectly verify innocence or guilt. Consequently, until these methods become more reliable, courts will likely continue to adhere to existing rules regarding the usage of lie detectors in court. Nevertheless, this does not mean that the usage of these tests cannot play a key role in investigations and cases. The power given to lie detector tests is justified because while they are not accurate enough to determine the difference between a guilty and innocent verdict, they can create leads and further clues during investigations. After all, a suspect could have a similar fate to Frank Sterling. However, its role in criminal investigations could be vital, like in the case of Annie Le. The tool of a polygraph test is a powerful one, and it should be used with other techniques to ensure justice for all.
Endnotes
(1) Sterling v. Bartlett, 214 F.R.D. 101
(2) “Killer Passes Polygraph, Innocent Man Fails, Killer Goes on to Kill Again | NITV Federal Services | the Manufacturer of the ‘Computer Voice Stress Analyzer’ - CVSA,” Cvsa1.com, 2022, https://www.cvsa1.com/press-releases/killer-passes-polygraph-innocent-man-fails-killer-goes-on-to-kill again/#:~:text=Ridgeway%20was%20dropped%20as%20a,of%20Death%E2%80%9D%2C%20Charles%20Cullen.
(3) “Lie Detector Test,” LII / Legal Information Institute, 2020, https://www.law.cornell.edu/wex/lie_detector_test#:~:text=Polygraphs%20measure%20physiological%20arousal%20factors,versus%20when%20the%20subject%20lies..
(4) Case IQ. “History of Detecting Deception,” April 19, 2023. https://www.caseiq.com/resources/ebook-how-to-detect-deception-in-investigation-interviews-history-of-detecting-deception/.
(5) John Synnott, David Dietzel & Maria Ioannou (2015) A review of the polygraph: history, methodology and current status, Crime Psychology Review, 1:1, 59-83, DOI: 10.1080/23744006.2015.1060080
(6) United States v. Frye, 293 F. 1013
(7) “Frye Standard,” LII / Legal Information Institute, 2022, https://www.law.cornell.edu/wex/frye_standard#:~:text=Frye%20Standard%20is%20used%20to,1923).
(8) Frye v. United States, 293 F. 1013 (D.C. Cir. 1923)
(9) Christina Majaski, “Are Lie Detector Tests Admissible in Court?,” LawInfo.com (LawInfo, May 18, 2020), https://www.lawinfo.com/resources/criminal-defense/are-lie-detector-tests-admissible-in-court.html#:~:text=As%20such%2C%20polygraph%20results%20are,or%20not)%20a%20polygraph%20exam.
(10) Ibid.
(11) Frye v. United States, 293 F. 1013 (D.C. Cir. 1923)
(12) “Killer Passes Polygraph, Innocent Man Fails, Killer Goes on to Kill Again | NITV Federal Services | the Manufacturer of the ‘Computer Voice Stress Analyzer’ - CVSA,” Cvsa1.com, 2022, https://www.cvsa1.com/press-releases/killer-passes-polygraph-innocent-man-fails-killer-goes-on-to-kill-again/.
(13) Polygraph Examiner, “Lie Detector Tests That Have Resolved Crimes - Lie Detector Test,” Lie Detector Test, May 29, 2023, https://liedetectortest.com/polygraph/lie-detector-tests-that-have-resolved-crimes.
(14) Jennifer Vogel and Madeleine Baran, “Inconclusive: The Truth about Lie Detector Tests,” Apmreports.org (APM Reports, September 20, 2016), https://www.apmreports.org/story/2016/09/20/inconclusive-lie-detector-tests#:~:text=The%20American%20Polygraph%20Association%2C%20which,70%20percent%20of%20the%20time
(15) “EyeDetect,” Converus, December 22, 2023, https://converus.com/eyedetect/#:~:text=During%20a%20test%2C%20participants%20answer,categorized%20as%20truthful%20or%20deceptive.
(16) Ibid.
