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Also known as a "lie detector," the polygraph has a controversial history in U.S. law. First developed in the late nineteenth century, its modern incarnation is an electromechanical device that is attached to a subject's body during an interview. The discipline of polygraphy is based on the theory that by recording involuntary physiological changes in the subject, the polygraph yields data that can be interpreted to determine whether the subject is telling the truth. Supporters of the scientific validity of the polygraph claim that results are approximately 90 percent accurate. For much of the twentieth century, however, polygraph evidence was inadmissible in criminal cases on grounds of unreliability. Polygraph evidence was admissible in civil cases, however, and it was also used widely in law enforcement, government, and industry.

Polygraphy uses a variety of formats. Until the 1950s the format was the relevant/irrelevant (R/I) test; it rested on the now discredited belief that a subject produces a specific identifiable physiological response when lying. The R/I test has been replaced by the control question (CQ) format, the only format routinely used in forensic tests. Typically, a trained examiner fits a subject with sensors to measure respiration, heart rate and blood pressure, and perspiration, which the polygraph records using pens on graph paper. The examiner asks a series of questions, including control questions that are designed to provoke anxiety and denial. Later, another examiner compares these answers with answers pertaining to the matter at hand. This is known as numerical CQ testing. So-called global CQ testing includes a more subjective component: one examiner scores the test while also factoring in the subject's observable physical responses, such as movement, expression, and voice.

In U.S. courts, the use of the polygraph was first addressed in 1923. In refusing to admit polygraph evidence in a murder case, the Court of Appeals for the District of Columbia created a legal standard that would last for nearly 70 years (Frye v. United States, 54 App. D.C. 46, 293 F. 1013 [1923]). This standard came to be known as the Frye rule, or general acceptance test. To be admissible in court, novel Scientific Evidence first must have gained general acceptance in its scientific field.

The Frye rule applied broadly to all scientific evidence, including polygraph evidence. Other appellate courts followed the court's standard throughout most of the century, primarily because polygraphy never gained widespread acceptance among scientists. Nonetheless, polygraph evidence was used in civil lawsuits, and police agencies, businesses, and government offices continued to use the polygraph regularly to provide evidence, screen job applicants, and investigate security risks.

Advances in polygraphy helped spur a judicial reevaluation, but more important was the adoption of the Federal Rules of Evidence in the 1970s. Rule 702 set an important new standard for the admission of scientific evidence:


Over the next two decades, appellate courts authorized use of polygraph evidence in a few state courts, a trend followed by the U.S. Court of Appeals for the Eleventh Circuit and the military courts. Then, in 1993, in a case not specifically related to the polygraph, the U.S. Supreme Court held that Rule 702 replaced the Frye test (Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S. Ct. 2786, 125 L. Ed. 2d 469). In essence, the Court said that the standard of general scientific acceptance was not as important as whether Expert Testimony can assist jurors. Soon thereafter, several federal courts reconsidered their long-standing ban on polygraph evidence and determined that they now had the discretion to permit its introduction at trial.

Congress also reexamined the use of the polygraph in industry. In 1988, lawmakers responded to civil liberty concerns about the abuse of polygraph testing in private industry by passing the Employee Polygraph Protection Act (29 U.S.C.A. §§ 2001 et seq.). The law bars preemployment testing in banking, retail, and other private industries and also makes it illegal for employers to fire, discriminate against, or discipline employees who refuse to submit to polygraph tests. The act exempts government employers, private industry when an employee is under investigation for economic injury suffered by the employer, and all security services and industries that manufacture, distribute, or dispense controlled substances.

In military trials, the situation was different. In United States v. Scheffer, 523 U.S. 303, 118 S. Ct. 1261, 140 L. Ed. 2d 413 (1998), the Supreme Court addressed the claim of airman Edward G. Scheffer that prohibiting the introduction of polygraph evidence during his Court-Martial (military criminal trial) violated his constitutional rights. Under Military Rule of Evidence 707, polygraph evidence is not allowed in court-martial proceedings. So, although Scheffer, who was accused of, among other things, taking illegal drugs, passed a polygraph, it was inadmissible as evidence. A federal court of appeals reversed the court-martial, stating that excluding the polygraph evidence did, in fact, violate Scheffer's right to present a defense as guaranteed by the Sixth Amendment. Upon review, the Supreme Court upheld Military Rule of Evidence 707. In the opinion of the Court, "State and federal governments unquestionably have a legitimate interest in ensuring that reliable evidence is presented to the trier of fact in a criminal trial." However, "there is simply no consensus that polygraph evidence is reliable."

Further readings

Arendell, Robert L., and Stephen C. Peters. 1996. "Revisiting the Admissibility of Polygraph Evidence After Daubert." Colorado Lawyer 25 (February).

McCall, James R. 1996. "Misconceptions and Reevaluation—Polygraph Admissibility After Rock and Daubert." University of Illinois Law Review.

Segrave, Kerry. 2004. Lie Detectors: A Social History. Jefferson, N.C.: McFarland.

Sleek, Scott. 1998. "Psychologists Debate Merits of the Polygraph." APA Monitor (June).


n. a lie detector device, from Greek for "many" (poly) "message" (graph) since numerous physiological responses are tested when questions are answered.

References in periodicals archive ?
Because of the peculiar nature of polygraph examination, however, and its inherent propensity to influence the jury, we have gone further and held that the mere mention of the taking of a polygraph examination without disclosure of the result is likewise error.
Privileged users and higher-risk individuals will be entered into a software program that will generate a monthly list of randomly selected individuals for counterintelligence polygraph examinations.
On information and belief, during the course of this investigation, the inmate was required to take a polygraph examination.
It is critical for the client to understand that a successful polygraph examination will be a valuable tool either at arbitration or as part of an effort to settle a case.
Almost two weeks later, SrA Freeman returned to the AFOSI office for the previously agreed upon polygraph examination.
First, the responses that occur and are recorded during a polygraph examination are sensitive to a host of factors that may be unrelated to deception.
The polygraph examination found that I was truthful and not deceptive in regard to my lack of any knowledge that the cooler and medications and substances had been placed in my barn on June 22, and as to my use of cobra venom or its use on my behalf.
The polygraph examination had a 92% accuracy rate in deceptive subjects and a 70% accuracy rate in truthful subjects.
Students were then told that they would be compensated for their participation in the study, but only after they took a polygraph examination that probed the truthfulness of their responses.
The other is based on utility: the idea that examinees, because they believe that deception may be revealed by the test, will be deterred from undesired actions that might later be investigated with the polygraph or induced to admit those actions during a polygraph examination.
Supreme Court held that either side could ban the results of a polygraph examination from use in a criminal trial because there is no consensus that polygraph evidence is reliable.
To evaluate the applicability of the guilty knowledge technique, 758 polygraph examination cases were surveyed for operable case facts (keys).