Last Updated 12 Apr 2021

History of Polygraph Test in the U.S.

Category Evidence, Justice
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Executive Summary The development of the polygraph test, to measure a suspect's honesty during interrogation, began in the 1890s. The modern polygraph test has been around since the 1930s. Wires connected to a suspect detect physiological changes and transfer that information to a graph, and a scientist then interprets the graph. The results are somewhat subjective. Honesty tests rely on psychological measurements rather than physiological measurements. Honesty tests ask a series of questions, such as whether the test subject would return a lost wallet, to determine the likelihood that he would be dishonest.

They are often used by employers before hiring or during investigations of employees suspected of corporate dishonesty. Both polygraph tests and honesty tests are highly controversial. Both require some level of subjective interpretation by the polygraph scientist or honesty test psychologist. For the polygraph tests, it is possible for examiners to manipulate the results by carefully crafting the questions to elicit higher physiological responses. Results are rarely admissible in court.


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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 underpinning the use of the polygraph 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 Berkeleyand a police officer of the Berkeley Police Department in Berkeley, California.

According to Encyclopedia, 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 psycho physiological detection of deception (PDD) examination. Testing procedure Today, polygraph examiners use two types of instrumentation: analog and computerized. In the United States, most examiners now use computerized instrumentation. A typical polygraph test starts with a pre-test interview to gain some preliminary information which will later be used for "control questions", or CQ.

Then the tester will explain how the polygraph is supposed to work, emphasizing that it can detect lies and that it is important to answer truthfully. Then a "stim test" is often conducted: the subject is asked to deliberately lie and then the tester reports that he was able to detect this lie. Guilty subjects are likely to become more anxious when they are reminded of the test's validity. However, there are risks of innocent subjects being equally or more anxious than the guilty. Then the actual test starts. Some of the questions asked are "irrelevant" or IR ("Is your name Chris? ), others are "probable-lie" control questions that most people will lie about ("Have you ever stolen money? ") and the remainders are the "relevant questions", or RQ, that the tester is really interested in. The different types of questions alternate. The test is passed if the physiological responses during the probable-lie control questions (CQ) are larger than those during the relevant questions (RQ). If this is not the case, the tester attempts to elicit admissions during a post-test interview, for example, "Your situation will only get worse if we don't clear this up".

Criticisms have been given regarding the validity of the administration of the Comparative Questions test (CQT). The CQT may be vulnerable to being conducted in an interrogation-like fashion. This kind of interrogation style would elicit a nervous response from innocent and guilty suspects alike. There are several other ways of administrating the questions. An alternative is the Guilty Knowledge Test (GKT), or the Concealed Information Test (CIT), which is being used in Japan. The administration of this test is given to prevent potential errors that may arise from the questioning style.

The test is usually conducted by a tester with no knowledge of the crime or circumstances in question. The administrator tests the participant on their knowledge of the crime that would not be known to an innocent person. For example: "Was the crime committed with a . 45 or a 9 mm? " The questions are in multiple choices and the participant is rated on how they react to the correct answer. If they react strongly to the guilty information, then proponents of the test believe that it is likely that they know facts relevant to the case.

This administration is considered more valid by supporters of the test because it contains many safeguards to avoid the risk of the administrator influencing the results. Validity Polygraphy has little evidence to support its use. Despite claims of 90% validity by polygraph advocates, the National Research Council has found no evidence of effectiveness. The utility among sex offenders is also poor with insufficient evidence to support accuracy or improved outcomes in this population.

Even using the high estimates of polygraph's accuracy a significant number of subjects will appear to be lying, and would unfairly suffer the consequences of "failing" the polygraph. In the 1998 Supreme Court case, United States v. Scheffer, the majority stated that "There is simply no consensus that polygraph evidence is reliable" and "Unlike other expert witnesses who testify about factual matters outside the jurors' knowledge, such as the analysis of fingerprints, ballistics, or DNA found at a crime scene, a polygraph expert can supply the jury only with another opinion... In 2005 the 11th Circuit Court of Appeals stated that “polygraphy did not enjoy general acceptance from the scientific community”. In 2001 William Iacono, Professor of Psychology and Neuroscience concluded that Although the CQT [Control Question Test] may be useful as an investigative aid and tool to induce confessions, it does not pass muster as a scientifically credible test. CQT theory is based on naive, implausible assumptions indicating (a) that it is biased against innocent individuals and (b) that it can be beaten simply by artificially augmenting responses to control questions.

Although it is not possible to adequately assess the error rate of the CQT, both of these conclusions are supported by published research findings in the best social science journals (Honts et al. , 1994; Horvath, 1977; Kleinmuntz & Szucko, 1984; Patrick & Iacono, 1991). Although defense attorneys often attempt to have the results of friendly CQTs admitted as evidence in court, there is no evidence supporting their validity and ample reason to doubt it.

Members of scientific organizations who have the requisite background to evaluate the CQT are overwhelmingly skeptical of the claims made by polygraph proponents. Summarizing the consensus in psychological research, Professor David W. Martin, PhD, from North Carolina State University, states that people have tried to use the polygraph for measuring human emotions, but there is simply no royal road to (measuring) human emotions. Therefore, since one cannot reliably measure human emotions (especially when one has an interest in iding his/her emotions), the idea of valid detection of truth or falsehood through measuring respiratory rate, blood volume, pulse rate and galvanic skin response is a mere pretense. Psychologists cannot ascertain what emotions one has, with or without the use of polygraph. Polygraphs measure physiological arousal which can pinpoint deception rather than "lies". National Academy of Sciences The accuracy of the polygraph has been contested almost since the introduction of the device. In 2003, the National Academy of Sciences (NAS) issued a report entitled "The Polygraph and Lie Detection".

The NAS found that the majority of polygraph research was "unreliable, unscientific and biased", concluding that 57 of the approximately 80 research studies that the APA relies on to come to their conclusions were significantly flawed. These studies did show that specific-incident polygraph testing, in a person untrained in counter-measures, could discern the truth at "a level greater than chance, yet short of perfection". However, due to several flaws, the levels of accuracy shown in these studies "are almost certainly higher than actual polygraph accuracy of specific-incident testing in the field".

When polygraphs are used as a screening tool (in national security matters and for law enforcement agencies for example) the level of accuracy drops to such a level that "Its accuracy in distinguishing actual or potential security violators from innocent test takers is insufficient to justify reliance on its use in employee security screening in federal agencies. " In fact, the NAS extrapolated that if the test were sensitive enough to detect 80% of spies (a level of accuracy which it did not assume), this would hardly be sufficient anyway.

Let us take for example a hypothetical polygraph screening of a body of 10,000 employees among which are 10 spies. With an 80% success rate, the polygraph test would show that 8 spies and 1,992 non-spies fail the test. Thus, roughly 99. 6 percent of positives (those failing the test) would be false positives. The NAS concluded that the polygraph "... may have some utility” but that there is "little basis for the expectation that a polygraph test could have extremely high accuracy. "

The NAS conclusions paralleled those of the earlier United States Congress Office of Technology Assessment report "Scientific Validity of Polygraph Testing: A Research Review and Evaluation”. Similarly, a report to congress by the Moynihan Commission on Government Secrecy on national security concluded that " The few Government-sponsored scientific research reports on polygraph validity (as opposed to its utility), especially those focusing on the screening of applicants for employment, indicate that the polygraph is neither scientifically valid nor especially effective beyond its ability to generate admissions.. . Countermeasures Several countermeasures designed to pass polygraph tests have been described. Asked how he passed the polygraph test, Aldrich Ames explained that he sought advice from his Soviet handler and received the simple instruction to: "Get a good night's sleep, and rest, and go into the test rested and relaxed. Be nice to the polygraph examiner, develop a rapport, and be cooperative and try to maintain your calm. " Additionally, Ames said, "`There's no special magic... Confidence is what does it. Confidence and a friendly relationship with the examiner... apport, where you smile and you make him think that you like him. Other suggestions for countermeasures include for the subject to mentally record the control and relevant questions as the examiner reviews them prior to commencing the interrogation. Once the interrogation begins, the subject is then supposed to carefully control their breathing during the relevant questions, and to try to artificially increase their heart during the control questions, such as by thinking of something scary or exciting or by pricking themselves with a pointed object concealed somewhere on their body.

In this way the results will not show a significant reaction to any of the relevant questions. Usage Law enforcement agencies and intelligence agencies in the United States are by far the biggest users of polygraph technology. In the United States alone all federal law enforcement agencies either employ their own polygraph examiners or use the services of examiners employed in other agencies. This is despite their unreliability. For example in 1978 Richard Helms, the 8th Director of Central Intelligence stated that: "We discovered there were some Eastern Europeans who could defeat the polygraph at any time.

Americans are not very good at it, because we are raised to tell the truth and when we lie it is easy to tell we are lying. But we find a lot of Europeans and Asiatics [who] can handle that polygraph without a blip, and you know they are lying and you have evidence that they are lying. " 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. [citation needed] 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, 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 law enforcement. Courts themselves do not order nor facilitate polygraph testing. In most cases, polygraph tests are voluntarily taken by a defendant in order to substantiate his or her defense. The Federal Court of Justice of Germany has ruled that polygraph evidence is inherently inconclusive and not admissible in court.

Motions by prosecution or defense for polygraph tests to be exercised will be declined under any circumstance. Canada In Canada, the polygraph is regularly used as a forensic tool in the investigation of criminal acts and sometimes employed in the screening of employees for government organizations. In the 1987 decision of R. v. Beland, the Supreme Court of Canada rejected the use of polygraph results as evidence in court. This decision did not, however, affect the use of the polygraph in criminal investigations. The polygraph continues to be used as an investigative tool. 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

  • 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.
  • The polygraph "expert" sought to express an opinion as to ultimate facts in issue, which is peculiarly the province of the jury.
  • 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.
  • 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. Israel The High Court of Israel, in Civil Appeal 551/89 (Menora Insurance Vs. Jacob Sdovnik), ruled that as the polygraph has not been recognized as a reliable device, polygraph results are inadmissible as evidence in a civil trial. In other decisions, polygraph results were ruled inadmissible in criminal trials. However, some insurance companies attempt to include a clause in insurance contracts, in which the beneficiary agrees that polygraph results be admissible as evidence. In such cases, where the beneficiary has willingly agreed to such a clause, signed the contract, and taken the test, the courts will honor the contract, and take the polygraph results into consideration.

Interestingly, it is common practice for lawyersto advise people who signed such contracts to refuse to take the test. Depending on whether or not the beneficiary signed an agreements clause, and whether the test was already taken or not, such a refusal usually has no ill effects; at worst, the court will simply order the person to take the test as agreed. At best, the court will cancel the clause and release the person from taking the test, or rule the evidence inadmissible.


Recently an Indian court adopted the brain electrical oscillations signature test as evidence to convict a woman, who was accused of murdering her fiance. It is the first time that the result of polygraph was used as evidence in court. On May 5, 2010, The Supreme Court of India declared use of narcoanalysis, brain mapping and polygraph tests on suspects as illegal and against the constitution. Article 20(3) of the Indian Constitution-"No person accused of any offence shall be compelled to be a witness against himself. " Polygraph tests are still legal if the defendant requests one. Security clearances

In the American military and intelligence communities, polygraphs have been administered both as terms of qualifying for a security clearance and as part of a periodic reinvestigation to retain a clearance. There is no uniform standard for whether the polygraph is needed, as some methods of adjudication do not demand a successful polygraph test to earn a clearance. Other agencies, particularly certain military units, actually prohibit polygraph testing on their members. According to a report to congress, polygraphy in the security clearance context has little utility in detecting untruth, but significant utility in inducing verbal admissions.

That is, polygraphy is mainly useful as a prop in the interrogation process. Further, this likely accounts for its continuing use by government agencies. It is difficult to precisely determine the effectiveness of polygraph results for the detection or deterrence of spying. Failure of a polygraph test could cause revocation of a security clearance, but it is inadmissible evidence in most federal courts and military courts martial. The polygraph is more often used as a deterrent to espionage rather than detection. One exception to this was the case of Harold James Nicholson, a CIA employee later convicted of spying for Russia.

In 1995, Nicholson had undergone his periodic five year reinvestigation where he showed a strong probability of deception on questions regarding relationships with a foreign intelligence unit. This polygraph test later launched an investigation which resulted in his eventual arrest and conviction. In most cases, however, polygraphs are more of a tool to "scare straight" those who would consider espionage. Jonathan was advised by his Israeli handlers that he was to resign his job from American intelligence if he was ever told he was subject to a polygraph test.

Likewise, John Anthony Walker was advised to by his handlers not to engage in espionage until he had been promoted to the highest position for which a polygraph test was not required, to refuse promotion to higher positions for which polygraph tests were required, and to retire when promotion was mandated. As part of his plea bargain agreement for his case of espionage for the Soviet Union, Robert Hanssen would be made to undergo a polygraph at any time as part of damage assessment. In Hanssen's 25-year career with the FBI, not once was he made to undergo a polygraph.

He later said that if he had been ordered to, he may have thought twice about espionage. Alternatively, the use of polygraph testing, where it causes desperation over dismissal for past dishonesty, may encourage spying. For example, Edward Lee Howard was dismissed from the CIA when, during a polygraph screening, he truthfully answered a series of questions admitting to minor crimes such as petty theft and drug abuse. In retaliation for his perceived unjust punishment for minor offenses, he later sold his knowledge of CIA operations to the Soviet Union. It is also worth noting that polygraph tests may not deter espionage.

From 1945 to the present, at least six Americans had been committing espionage while they successfully passed polygraph tests. Two of the most notable cases of two men who created a false negative result with the polygraphs were Larry Wu-Tai Chin and Aldrich Ames. Ames was given two polygraph examinations while with the CIA, the first in 1986 and the second in 1991. The CIA reported that he passed both examinations after experiencing initial indications of deception. According to a Senate investigation, an FBI review of the first examination concluded that the indications of deception were never resolved.

The Senate committee reported that the second examination, at a time when Ames was under suspicion, resulted in indications of deception and a retest a few days later with a different examiner. The second examiner concluded that there were no further indications of deception. In the CIA's analysis of the second exam, they were critical of their own failure to convey to their examiner the existing suspicions that were not addressed in the examination. In August 2008, the US Defense Intelligence Agency announced that it would subject each of its 5,700 prospective and current employees to a polygraph interrogation at least once annually.

In 2012, a McClatchy investigation found that the National Reconnaissance Office was possibly breaching ethical and legal boundaries by encouraging its polygraph examiners to extract personal and private information from subjects during polygraph interrogations. Alternative tests Most polygraph researchers have focused more the exam's predictive value on a subject’s guilt. However, there have been no empirical theories established to explain how a polygraph measures deception. Recent research indicates that Functional Magnetic Resonance Imaging (fMRI) may benefit in explaining the psychological correlations of polygraph exams.

It could also explain which parts of the brain are active when subjects use artificial memories. Most brain activity occurs in both sides of the ventrolateral prefrontal cortex, which is linked to response inhibition. This indicates that deception involves a subject’s inhibition of certain questions, such as attempting to be truthful while lying. Recalling artificial memories are known to activate the posterior cingulate cortex. However, fMRIs are limited to being expensive, immobile, and having inconsistent lying responses.

Some researchers believe that reaction time (RT) based tests may replace polygraphs in concealed information detection. RT based tests differ from polygraphs in stimulus presentation duration, and can be conducted without physiological recording as subject response time is measured via computer. However, researchers have found limitations to these tests as subjects voluntarily control their reaction time, deception can still occur within the response deadline, and the test itself lacks physiological recording. Society and culture

Lie detection has a long history in mythology and fairy tales; the polygraph has allowed modern fiction to use a device more easily seen as scientific and plausible. Notable instances of polygraph usage include uses in crime and espionage themed television shows and some daytime television talk shows, cartoons and films. The most notable polygraph TV show is Lie Detector, which first aired in the 1950s created and hosted by Ralph Andrews. Then in the 1960s Ralph produced a series of specials hosted by Melvin Belli, then in the 1970s hosted by Jack Anderson.

In 1998 TV producer Mark Phillips with his Mark Phillips Philms & Telephision put Lie Detector back on the air on the FOX Network—on that program Dr. Ed Gelb with host Marcia Clark cleared Mark Fuhrman from the allegation that he "planted the bloody glove. " Later Phillips produced Lie Detector as a series for PAX/ION—some of the guests included Paula Jones, Reverend Paul Crouch accuser Lonny Ford, Ben Rowling, Jeff Gannon and Swift Boat Vet, Steve Garner. FOX has taken this one step further with their game show The Moment of Truth which pits people's honesty against their own sense of modesty, propriety, etc.

Contestants are given a polygraph test administered by a polygraph expert in a pre-screening session answering over 50 questions. Later they must sit in front of a studio audience including their friends & family for the televised portion of the show. There they need only answer 21 answers truthfully "as determined by the polygraph" to win $500,000. The questions get more personal and/or more revealing as they advance. Most polygraph experts caution that the polygraph techniques used on Moment of Truth do not conform to any known or accepted methods of polygraphy. citation needed] Daytime talk shows, such as Maury Povich and Steve Wilkos, frequently use lie detectors to tell if someone is cheating on their significant other. In one MacGyver episode 'Slow Death', MacGyver assists the Indian tribesmen by improvising a polygraph to weed out the crooked doctor. This is made possible by using an analog sphygmomanometer to monitor blood pressure change, and an electronic alarm clock to detect sweat. To test its reliability, MacGyver asked a passenger on the train a few 'placebo' questions.

The culprit was only discovered when he was trying to hide his crime, thus his sweat triggered the alarm clock and blood pressure climbed up. In the movie Harsh Times the protagonist, played by actor Christian Bale, is caught trying to "beat" a polygraph test during a pre-employment screening for a federal law enforcement job. He stores a tack in the toe of his shoe and uses the pain sensation to mask his true apprehension of certain questions. The polygraph is immediately suspicious and the examination is ended.

In the movie Ocean's 13, one of the characters beats a polygraph test by stepping on a tack when answering truthfully, which supposedly raises the polygraph's readings for the truthful answers so they equal the deceptive ones. In the television series Profit, there is a memorable sequence at the end of episode "Healing" where the eponymous character, Jim Profit, manages to fool a polygraph. He does that by putting a nail through the sole of his shoe and pushing it inside of his heel while answering every question in order to even out the readings. This scene is very graphic, especially for its time, 1996.

During a voice over, Profit explains the theory behind the polygraph and the flaws he intends to exploit in it. In episode 93 of the USA popular science show Myth busters, they attempted to fool the polygraph by using pain to try to increase the readings when answering truthfully (so the machine will supposedly interpret the truthful and non-truthful answers as the same. ) They also attempted to fool the polygraph by thinking happy thoughts when lying and thinking stressful thoughts when telling the truth to try to confuse the machine. However, neither technique was successful for a number of reasons.

Michael Martin correctly identified each guilty and innocent subject. The show also noted the opinion that, when done properly, polygraphs are correct 80-99% of the time. In the case of police employment you will be advised that a copy of the test results will be provided to the police department you applied to, and that you will not be asked questions concerning such areas as political activities, racial or religious beliefs, or sexual activities.

The remainder of the pretest interview focuses on the specific questions you will be asked during the examination. These may include questions about your prior employment, driving record, drug use, and criminal history. The examiner wants to learn enough to assess your readiness for the examination and to prepare anxiety-provoking control questions. The polygraph examiner will then explain the polygraph technique to you before starting the actual examination. »Polygraph exam questions Gone are the days a polygraph examiner asked if you ever had sex with a farm animal.

Pre-employment polygraph examinations fall under the guidelines for employment interviewing of title VII of the Equal Employment Opportunity Commission, so examiners are obliged to conduct the examinations in a way that would not discriminate on the basis of sex, race, etc. One central principle of ethical standards is that relevant questions be related to the job applied for. Here are typical questions asked on the police polygraph test:

  • Did you tell the complete truth on your job application? Have you deliberately withheld information from your job application?
  • Have you ever been fired from a job?
  • Since the age of have you committed an undetected crime?
  • Since the age of ( ) have you been convicted of a crime?
  • During the past year, have you used marijuana more than ( ) per ( )?
  • Have you used any other narcotic illegally in the past years?
  • Have you sold marijuana or other narcotics illegally in the past years?
  • Have you ever stolen more than ($ ) worth of merchandise in any one year from any of your employers?
  • Have you even stolen more than ($ ) in moneys in any one year from any of your employers?
  • Have you ever used a system to cheat one of your employers?
  • Have you ever had your driver’s license suspended or revoked? Have you ever had any traffic citations in the past five ( ) years?
  • Have you deliberately lied to any of these questions?

Values, such as age and number of years is determined by the specific department. The method used by John E. Reid & Associates employs four standard relevant questions:

  • In the last five years did you steal any merchandise from previous employers?
  • In the last five years did you steal any money from previous employers?
  • In the last ten years did you take part in or commit any serious crime?
  • Did you falsify any information on your application?
  • These standard questions may be modified depending on admissions made during the pretest (e. g. , a revision may be, “In the last five years did you steal any merchandise other than minor office supplies? ").

In addition to the standard questions a fifth relevant question (e. g. , concerning the illegal purchase or sale of merchandise; use of narcotics) may be added. The Reid firm also uses what it regards as control questions in pre-employment interviews.

Control questions include, “Did you ever steal anything in your life? " and “Did you lie to any of the questions you answered during the application process for this job? " It is not clear, however, how the Reid pre-employment control questions differ from the relevant questions. It seems reasonable to suppose that both truthful and non-truthful subjects (in terms of the relevant questions) may be just as concerned with the subject matter of the control questions as they are with the relevant questions. It is also not clear why employers would be less concerned with the control than with the relevant questions.


Some firms still use the polygraph (or lie detector) for honesty testing, although current law severely restricts its use. The polygraph is a device that measures physiological changes like increased perspiration. The assumption is that such changes reflect changes in emotional state that accompany lying. Complaints about offensiveness plus grave doubts about the polygraph’s accuracy culminated in the Employee Polygraph Protection Act of 1988. With a few exceptions the law prohibits employers from conducting polygraph examinations of all job applicants and most employees. Also prohibited under this law are other mechanical or electrical devices that attempt to measure honesty or dishonesty, including psychological stress evaluators and voice stress analyzers. Federal laws don’t prohibit paper and pencil tests and chemical testing. Polygraph examinations are scientific tests that are rooted in the fundamental laws of psychology and physiology. The interviewee's bodily reactions to her answers are analyzed in accordance to years of study on the human psyche. This scientific method claims direct access to the subject's memory, which is inaccessible by orthodox means of investigation. Polygraph tests are solely conducted on persons who are mentally and physically sound. There are no accusations, simply questions answerable by "yes" or "no. " The examiner is neutral, which, according to the Euro Polygraph Center, enables the subject "to free himself of any prejudice in connection to his examination and of any external sources of stress. " These tests can also be administered to gauge the honesty of potential employees.

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