polygraph

Definition of polygraph

Noun

polygraph (plural polygraphs)

1. A device which measures and records several physiological variables such as blood pressure, heart rate, respiration and skin conductivity while a series of questions is being asked to a subject, in an attempt to detect lies.
2. (dated) An mechanical instrument for multiplying copies of a writing, resembling multiple pantographs.
3. (archaic) A collection of different works, either by one or several authors.

Synonyms

• (device recording physiological measurements): lie detector
• (dated instrument for copying): manifold writer, autopen

Verb

polygraph (third-person singular simple present polygraphs, present participle polygraphing, simple past and past participle polygraphed)

1. To administer a polygraph test.
   
   The FBI polygraphed the suspect but learned nothing because they already knew he was lying.

Further reading

A polygraph (popularly referred to as a lie detector) measures and records several physiological indices such as blood pressure, pulse, respiration, and skin conductivity while the subject is asked and answers a series of questions. The belief is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers.

The polygraph was invented in 1921 by John Augustus Larson, a medical student at the University of California at Berkeley and a police officer of the Berkeley Police Department in Berkeley, California. According to Encyclopædia Britannica, the polygraph was on its 2003 list of greatest inventions, described by the company as inventions that "have had profound effects on human life for better or worse."

Many members of the scientific community consider polygraphy to be pseudoscience. Nonetheless, in some countries polygraphs are used as an interrogation tool with criminal suspects or candidates for sensitive public or private sector employment. US federal government agencies such as the FBI and the CIA and many police departments such as the LAPD use polygraph examinations to interrogate suspects and screen new employees. Within the US federal government, a polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination.

Admissibility of polygraphs in court

United States

In 2007, polygraph testimony was admitted by stipulation in 19 states, and was subject to the discretion of the trial judge in federal court. The use of polygraph in court testimony remains controversial, although it is used extensively in post-conviction supervision, particularly of sex offenders. In Daubert v. Merrell Dow Pharmaceuticals (1993), the old Frye standard was lifted and all forensic evidence, including polygraph, had to meet the new Daubert standard in which "underlying reasoning or methodology is scientifically valid and properly can be applied to the facts at issue." While polygraph tests are commonly used in police investigations in the US, no defendant or witness can be forced to undergo the test. In United States v. Scheffer (1998), the U.S. Supreme Court left it up to individual jurisdictions whether polygraph results could be admitted as evidence in court cases. Nevertheless, it is used extensively by prosecutors, defense attorneys, and law enforcement agencies. In the States of Massachusetts, Maryland, New Jersey, Delaware and Iowa it is illegal for any employer to order a polygraph either as conditions to gain employment, or if an employee has been suspected of wrongdoing. The Employee Polygraph Protection Act of 1988 (EPPA) generally prevents employers from using lie detector tests, either for pre-employment screening or during the course of employment, with certain exemptions.

In the United States, the State of New Mexico admits polygraph testing in front of juries under certain circumstances. In many other states, polygraph examiners are permitted to testify in front of judges in various types of hearings (Motion to Revoke Probation, Motion to Adjudicate Guilt).

Europe

In most European jurisdictions, polygraphs are not considered reliable evidence and are not generally used by police forces. Courts themselves do not order or pay for polygraph tests. In most cases, polygraph tests are voluntarily taken by a defendant in order to substantiate his or her claims.

The Federal Court of Justice of Germany has ruled that polygraph evidence is not admissible in court.

Australia

The High Court of Australia has not yet considered the admissibility of polygraph evidence. However, the New South Wales District Court rejected the use of the device in a criminal trial. In Raymond George Murray 1982 7A Crim R48 Sinclair DCJ refused to admit polygraph evidence tending to support the defence. The judge rejected the evidence because

1. The veracity of the accused and the weight to be given to his evidence, and other witnesses called in the trial, was a matter for the jury.
2. The polygraph "expert" sought to express an opinion as to ultimate facts in issue, which is peculiarly the province of the jury.
3. The test purported to be expert evidence by the witness who was not qualified as an expert, he was merely an operator and assessor of a polygraph. The scientific premise upon which his assessment was based had not been proved in any Court in Australia.
4. Devoid of any proved or accepted scientific basis, the evidence of the operator is hearsay which is inadmissible.

The Court cited, with approval, the Canadian case of Phillion v R 1978 1SCR 18.

Lie detector evidence is currently inadmissible in New South Wales courts under the Lie Detectors Act.