By: Madeline Stoeri
Published: March 8, 2026
Few inventions or ideas that were considered cutting-edge in the 1920s remain so nearly one hundred years later. Even fewer continue to cause controversy. The polygraph, however, is a bit of an anomaly. Emerging from the combined contributions of William Marston, John Larson, and Leonarde Keeler, the polygraph is legally defined as an instrument that “(A) records continuously, visually, permanently, and simultaneously changes in cardiovascular, respiratory, and electrodermal patterns as minimum instrumentation standards; and (B) is used, or the results of which are used, for the purpose of rendering a diagnostic opinion regarding the honesty or dishonesty of an individual.”[1] Essentially, a polygraph machine measures the changes or lack of changes in a subject’s heart rate, respiration, and skin conductivity while answering questions; this data is used by the polygraph examiner to infer the subject’s truthfulness or deceptiveness.[2] The polygraph continues to be used today in pre-employment screenings for government employees and applicants to federal agencies, even though polygraphs are usually not admissible in court,[3] the theoretical basis for polygraphy has been shown to lack any scientific validity, and the use of this pseudo-scientific technique disproportionately harms and deters diverse applicants.[4]
The basic theory underlying the use of polygraphs is that someone being deceptive will fear getting caught and this fear of detection will produce measurable physiological reactions.[5] Thus, polygraphs actually measure the fear of being caught rather than deceptiveness.[6] Moreover, the physiological reactions measured may be created by causes other than deception and fear of detection such as, for example, anxiety about being tested.[7] Furthermore, evidence suggests that polygraph subjects who are members of a socially stigmatized group or who are believed to be guilty by the examiner may display physiological responses in polygraph test situations that indicate deceptiveness to the examiner, regardless of their actual honesty.[8]
Aside from the problematic theory underlying polygraph examinations, there are significant problems with measuring the validity of polygraphs, the availability of countermeasures leading to false negatives, and the frequency of false positives.[9] In terms of measuring the validity of polygraph examinations, studies are generally conducted either in the field or in laboratory settings.[10] Field studies mostly rely on instances in which polygraphs are used pursuant to a particular investigation, rather than in pre-employment screenings, and often suffer from a lack of clarity regarding the truth against which examination results can be judged.[11] In a laboratory setting, subjects are generally aware of the low-stakes consequences for lying or being found deceptive and therefore do not reflect similar stress levels as subjects in the field.[12]
More concerning than the lack of rigorous research on the validity of polygraphs is the evidence of both false negatives and false positives.[13] A false negative on a polygraph examination occurs when a subject manages to “pass” the polygraph while being deceptive; essentially a subject lies, yet is not detected.[14] A multitude of strategies like well-timed movement, consuming certain medications or substances prior to the examination, and employing psychological strategies such as training in bio-feedback techniques, may help a subject successfully “pass” a polygraph examination despite lying.[15] In fact, when it comes to skin conductivity, essentially a measure of how much a subject is sweating during a polygraph examination, research suggests a correlation between lower skin conductivity and psychopathy.[16]
However, the strongest evidence has been gathered to demonstrate the frequency of false positives in polygraph examinations.[17] In this context, a false positive occurs when a subject is determined to be deceptive or a polygraph examination is deemed inconclusive when the subject is, in fact, honest with examiners.[18] In 1983, a review conducted by the Office of Technology Assessment concluded that the likelihood of false positives in polygraph examinations is highest when polygraphs are used for screening purposes, such as in pre-employment screenings.[19]
The lack of consensus in the scientific community and the myriad of problems with polygraphy eventually led Congress to enact the 1988 Employee Polygraph Protection Act.[20] While this statute prohibited the routine use of polygraphs by employers in the private sector, the use of polygraphs in pre-employment screening for federal jobs continued.[21] Unfortunately, due to the unreliable and unscientific nature of polygraphs, minority candidates disproportionately fail pre-employment polygraph screenings.[22] For example, a federal court in 2007 noted that in one year, Black applicants to the Arkansas State Police force failed polygraphs nearly twice as often as white applicants.[23] Similarly, a review of available data on FBI applicants between 2008 and 2010 indicated a disproportionate polygraph failure rate for Black, Native American, Asian, Hispanic, and Pacific Islander candidates, while simultaneously suggesting a disproportionately high polygraph passage rate for white candidates.[24] Essentially, the unscientific nature of the polygraph results in an outcome––passage or failure of the test––that can be determined by the polygraph examiner’s biases, prejudices, and moods.[25] Combine this reality with the fact that failing a polygraph can cost a candidate the job in question, and may also detrimentally affect any future job applications as candidates required to submit to a polygraph examination are often asked to report any previous polygraph failures.[26] As polygraph failures must be reported, yet can occur for a number of reasons, minority candidates and those with mental health conditions like anxiety are likely to be deterred from even applying to jobs requiring a polygraph examination.[27] Even if such candidates do apply, their chances of passing the polygraph are lower.[28] Considering the importance of diverse viewpoints in identifying and assessing security risks, as well as in formulating policies and laws, the exemption allowing for the use of polygraphs in federal pre-employment screening ensures only one thing: that minority and neurodiverse applicants are less likely to be hired at the federal level.
[1] 29 U.S.C.S. § 2001(4).
[2] See 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), https://sgp.fas.org/othergov/polygraph/ota/summary.html [hereinafter OTA Memorandum].
[3] See Don Grubin & Lars Madsen, Lie Detection and the Polygraph: A Historical Review, 16 J. of Forensic Psychiatry & Psych. 357, 361 (2005).
[4] See OTA Memorandum, supra note 2; Veazey v. Commc’ns & Cable, Inc., 194 F.3d 850, 855-56 (7th Cir. 1999); Mark Harris, The Lie Generator: Inside the Black Mirror World of Polygraph Job Screenings, WIRED (Oct. 1, 2018, 7:00 AM), https://www.wired.com/story/inside-polygraph-job-screening-black-mirror/.
[5] See The Polygraph and Lie Detection, Nat’l Rsch. Council 13 (2003).
[6] See Nat’l Rsch. Council, supra note 5 at 7 (explaining that the physiological changes a polygraph machine measures actually reflect a subject’s fear – possibly but not necessarily associated with deception – and not any physiological response scientifically linked to deception).
[7] See Nat’l Rsch. Council, supra note 5 at 72 (describing the pre-polygraph examination interview and the assumption that emphasizing the examination’s supposed accuracy will put truthful subjects at ease and increase anxiety only in deceptive subjects); Harris, supra note 4 (noting the concerns of many scientists that the physiological changes measured by polygraph examinations can be caused by a variety of emotions and reactions other than deception, including nervousness, arousal, anxiety, and fear).
[8] See Nat’l Rsch. Council, supra note 5 at 3 (directly stating that “there is evidence suggesting that truthful members of socially stigmatized groups and truthful examinees who are believed to be guilty or believed to have a high likelihood of being guilty may show emotional and physiological responses in polygraph test situations that mimic the responses that are expected of deceptive individuals.”).
[9] See OTA Memorandum, supra note 2 at 4 (noting that no overall conclusion or single judgment of polygraph validity can be reached based on the scientific evidence available).
[10] See OTA Memorandum, supra note 2 at 39 (clarifying that studies done on polygraph validity have relied on either field tests – such as observing polygraph examinations of suspects – where the researcher has no experimental control, or laboratory tests where the subjects of the polygraph are not under the same pressures as a criminal investigation or employment pre-screening).
[11] See Nat’l Rsch. Council, supra note 5 at 4 (emphasizing that laboratory conditions involve less variations than those that arise in field applications of polygraph examinations).
[12] See Nat’l Rsch. Council, supra note 5 at 61 (enunciating the fact that polygraph subjects in laboratory – or analog – studies face significantly different consequences for either lying or being detected lying than subjects in field studies who are generally suspects or criminals facing charges).
[13] See Harris, supra note 4 (noting that the Department of Energy was particularly concerned about the prevalence of false positives in polygraph examinations, leading to a 2005 study by the DOE concluding that false positives clearly affect morale).
[14] See Harris, supra note 4.
[15] See OTA Memorandum, supra note 2, at 5.
[16] See R. D. Hare, Psychopathy and Electrodermal Responses to Nonsignal Stimulation, 6 Bio. Psych. 237, 237 (1978).
[17] See OTA Memorandum, supra note 2, at 5.
[18] Id. at 38.
[19] See Nat’l Rsch. Council, supra note 5, at 12.
[20] See generally 29 U.S.C. §§ 2001–2009.
[21] 29 U.S.C. §§ 2002, 2006.
[22] See Harris, supra note 4; see also Jay Stanley, How Lie Detectors Enable Racial Bias, ACLU (Oct. 2, 2018), https://www.aclu.org/news/privacy-technology/how-lie-detectors-enable-racial-bias.
[23] See Harris, supra note 4.
[24] Id.
[25] Id.
[26] Id.
[27] Id.
[28] Id.