You are viewing an archived webpage. The information on this page may be out of date. Learn about EPIC's recent work at

Polygraph Testing

Overview of the Polygraph

A polygraph machine records the body's involuntary responses to an examiner's questions in order to ascertain deceptive behavior. The test measures physiological data from three or more systems of the human body-generally the respiratory, cardiovascular, and sweat gland systems-but not the voice. There are other tests that test the voice for deception.

"Polygraph"means literally "many writings," referring to the method of recording several physiological activities at the same time. William M. Marston invented the first lie detector in 1917. Marston claimed he could reveal verbal deception by observing levels of systolic blood pressure. However, in 1923, the D.C. Court of Appeals stated that there was not enough scientific evidence to support Matston's lie detector machine. Roughly a century later, Leonarde Keeler invented a machine and school for examiners that paved the way for the modern use of polygraph testing, especially in the legal realm.

Polygraph testing is mainly done for law enforcement, judicial and the private business sector purposes. Private business sector use of the polygraph is restricted under the Employee Polygraph Protection Act of 1988 ("EPPA").

The EPPA's Privacy Protections

The EPPA was enacted to establish guidelines for examination conducted by private commercial employers, with a few exceptions for positions related to state security and positions under government contract. Generally, an employer cannot require a pre-employment polygraph test of an applicant. Even when an employer can request that an employee take a polygraph test, certain criteria must be met. An employer cannot fire an employee for refusing to take a polygraph test.

As an additional safeguard, the majority of states insist that polygraph examiners qualify for a license to conduct examinations.

  • Some examples of the variation of state regulation of polygraph testing other than that of the EPPA:
    • New York."No employer or his agent shall require, request, suggest or knowingly permit any employee or prospective employee of such employer to submit to a psychological stress evaluator examination and no employer shall administer or utilize the results of such test within or without the state of New York for any reason whatsoever." N.Y. Lab. Law § 735.
    • California."No employer shall demand or require any applicant for employment or prospective employment or any employee to submit to or take a polygraph, lie detector or similar test or examination as a condition of employment or continued employment. The prohibition of this section does not apply to the federal government or any agency thereof or the state government or any agency or local subdivision thereof, including, but not limited to, counties, cities and counties, cities, districts, authorities, and agencies." Cal. Labor Code § 432.2.
    • Florida."As part of a treatment program [for sex offenders], participation in a minimum of one annual polygraph examination to obtain information necessary for risk management and treatment and to reduce the sex offender's denial mechanisms. The polygraph examination must be conducted by a polygrapher trained specifically in the use of the polygraph for the monitoring of sex offenders, where available, and at the expense of the sex offender. The results of the polygraph examination shall not be used as evidence in a hearing to prove that a violation of supervision has occurred." Fla. Stat. Ann. § 947.1405 (10)(b)(1).

Reliability of Polygraph Testing

Because the polygraph test measures bodily responses, a data subject can attempt to alter her bodily responses in order to interfere with the test. Several common ways to undermine the test include: taking sedatives to reduce anxiety; using antiperspirant to prevent sweating; and positioning pins or biting parts of the mouth after each question to demonstrate a constant physiological response.

In 2002, a panel from the National Academy of Sciences were charged with "conduct[ing] a scientific review of the research on polygraph examinations that pertains to their validity and reliability, in particular for peronnel secutiry screening." The panel's findings were compiled into the report, "The Polygraph and Lie Detection," and presented to Congress and the Department of Energy. The panel found polygraph testing to be unscientific because it lacked fixed standards. After reiviewing the available data and studies on polygraph testing, the panel concluded: "Almost a century of research in scientific psychology and physiology provides little basis for the expectation that a polygraph test could have extremely high accuracy." Further, there was little hope for advancing polygraph testing. According to the panel's findings: "The inherent ambiguity of the physiological measures used in the polygraph suggest that further investments in improving polygraph technique and interpretation will bring only modest improvements in accuracy."

Based on the National Academy of Science's report, Congress required the Department of Energy to reconsider their polygraph use in light of the study's findings. However, the Department of Energy retained and resubmitted their existing poligraph policy to Congress, stating that, regardless of the panel's conclusions, the rules constituted "a balanced approach for the carefully circumscribed use of polygraph examinations as a tool that appears in current circumstances well-suited to accomplish the Congressionally-specified purpose 'to minimize the potential for release or disclosure of classified data, materials, or information.'"

Notwithstanding the controversy surrounding the use of polygraph examinations, the Department of Defense has expressed interest in increasing the use of them for secutiry and counterintelligence.

Protect your Privacy

Even advocates of polygraph test admit to the existence of erroneous results. Errors can be attributed to a number of factors, which include the preparation of the subject for examination, the examiner's approach to questions, the examiner's interpretation of the results, and the subject's nervousness and anxiety.

If an examination results in a false positive, i.e. the test indicates that a subject is deceptive when he is not, the subject should request a second examination and have a different examiner conduct the test. In addition, the subject should also complain to any of the following: the state licensing board; the Department of Labor under the EPPA; or the American Polygraph Association. The Department of Labor maintains a compliance page with regard to the EPPA.


  • Taylor Bright, D.A. Targets Irondale; Drug case against official's son probed, Birmingham Post-Herald, July 3, 2003.
  • Jeff Daniel, Lies, Damned Lies . . . And Truth?; The Polygraph Machine, A Settled Part of Crime Fiction, Remains, In Fact, Controversial, St. Louis Post-Dispatch (Missouri), May 4, 2003.
  • Petula Dvorak and Allan Lengel, Levy family seeks Condit polygraph - Family doubts lawmaker has revealed all, The Washington Post, July 9, 2001.
  • Greg Krikorian and Scott Glover, Lie Detector Test an Issue in Spy Case; It was suggested that suspect be tested in the mid-1990s, U.S. officials say, but she was not, Los Angeles Times, May 2, 2003.
  • Mike Levsen, Polygraph Tests as Good as Tea Leaves,, July 22, 2003.
  • Alan P. Zelicoff, Opinion, Polygraphs: Worse than Worthless, Washington Post, May 27, 2003.


  • The Accuracy and Utility of Polygraph Testing, Washington, DC: U.S. Department of Defense (1984) (supporting the validity and reliability of polygraph testing).
  • ACLU, Briefing Paper, Lie Detector Testing(1996).
  • American Polygraph Association. The professional association dedicated to furthering the use of polygraph testing.
  • A comprehensive site dedicated to criticizing polygraph testing and providing information on how to "beat" the test.
  • DoD Polygraph Institute. The Department of Defense's educational institution offering courses for polygraph examiners.
  • Brad V. Driscoll, Note, The Employee Polygraph Protection Act of 1988: A Balance of Interests, 75 Iowa L. Rev. 539 (1990).
  • Fact File: A Complendium of DARPA Programs, The Defense Advanced Reserach Projects Agency, (Aug. 2003).
  • Federation of American Scientists' Polygraph Policy. A non-profit organization advocating a scientific approach to public policy.
  •'s explanation of polygraph testingand lie-detectorsin general
  • The Polygraph Place. Commercial site offering contact information for polygraph examiners.
  • Issues Surrounding the Use of Polygraphs: Hearing Before the Senate Comm. on the Judiciary, 107 Cong. (April 25, 2001).
  • A Review of the Federal Bureau of Investigation Laboratory, Beyond the Inspector General Report: Hearing Before the Subcomm. on the Admin. Oversights & the Cts. of the Senate Comm. on the Judiciary, 105 Cong. (Sept. 29, 1997).
  • Susan McCarthy, The Truth about the Polygraph, Salon (Mar. 2, 2000).
  • Larry D. Scheafer, Refusal to Submit to Polygraph Examination as Grounds for Discharge or Suspension of Public Employees or Officers, 15 A.L.R.4th 1207 (1982).


  • United States v. Scheffer , 523 U.S. 303 (1998). The United States Supreme Court examined the admissibility of polygraph results in court, stating:

    The contentions of respondent and the dissent not withstanding, there is simply no consensus that polygraph evidence is reliable. To this day, the scientific community remains extremely polarized about the reliability of polygraph techniques. Some studies have concluded that polygraph tests overall are accurate and reliable. See, e.g., S. Abrams, The Complete Polygraph Handbook 190-191 (1968) (reporting the overall accuracy rate from laboratory studies involving the common "control question technique" polygraph to be "in the range of 87 percent"). Others have found that polygraph tests assess truthfulness significantly less accurately - that scientific field studies suggest the accuracy rate of the "control question technique" polygraph is "little better than could be obtained by the toss of a coin," that is, 50 percent.

Share this page:

Defend Privacy. Support EPIC.
US Needs a Data Protection Agency
2020 Election Security