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Frequently Asked Questions

What is a polygraph?

The term "polygraph" literally means "many writings." The name refers to the manner in which selected physiological activities are simultaneously recorded. Polygraph examiners my use conventional instruments, sometimes referred to analog instruments, or computerized instruments. It is important to understand what a polygraph examination entails. A polygraph will collect physiological data from at least three systems in the body.

Corrugated rubber tubes (or electronic sensors) placed over the examinee's chest and abdominal area will record respiratory activity. Two small metal plates or disposable adhesive electrodes, attached to the fingers, will record sweat gland activity, and a blood pressure cuff or similar device will record cardiovascular activity. Some instruments also monitor other activity. For example, a finger plethysmograph, which monitors blood volume in a fingertip, or motion sensors, which monitor general movements that might interfere with test data, are often used. It is important to note that a polygraph does not include the analysis of physiology associated with the voice. Instruments that claim to record voice stress are not polygraphs and have not been shown to work any better than chance (i.e. accuracy is similar to making a decision based on a coin toss).

A typical polygraph examination will include a period referred to as a pre-test interview, a chart collection phase and a test data analysis phase. During the pre-test, the polygraph examiner will complete required paperwork and talk with the examinee about the test, answering any questions the examinee might have. It is during this phase that the examiner will discuss the test questions and familiarize the examinee with the testing procedure. During the chart collection phase the examiner will administer and collect a number of polygraph charts. The number of questions and the number of charts will vary, depending on the number of issues and technique employed. Following this, the examiner will analyze the charts and render an opinion as to the truthfulness of the examinee. The examiner, when appropriate, will offer the examinee an opportunity to explain physiological responses in relation to one or more questions presented during the test.

Who uses the polygraph?

The four sectors that use the polygraph include law enforcement agencies, the legal community, government agencies, and the private sector. They are further described as follows:

•Law Enforcement Agencies

- Federal law enforcement agencies, state law enforcement agencies, and local law enforcement agencies such as police and sheriff's departments.

• Legal Community

•Government Agencies

•Private Sector

What is the Employee Polygraph Protection Act? (EPPA)

See our comprehensive page on this subject by clicking here.

Polygraph Screening in Police Agencies: The Employee Polygraph Protection Act of 1988 (EPPA) prohibits most private employers from using polygraph testing to screen applicants for employment. It does not affect public employers such as police agencies or other governmental institutions. In the testimony regarding EPPA it became clear that there were no current and reliable data on a variety of important issues about police applicant screening, although polygraph testing had reportedly been used for that purpose since at least the early 1950's. In recognition of this gap, the APA Research Center at Michigan State University conducted a survey of police executives in the U.S. to determine the extent of, and conditions in which polygraph testing was being used for pre-employment screening. The survey sample included 699 of the largest police agencies in the United States, excluding federal agencies, and produced usable returns from 626 agencies, a response rate of 90%. The major results of the survey showed the following:

Among the respondents, 62% had an active polygraph screening program, 31% did not and 7% had discontinued polygraph screening, usually because of prohibitive legislation. These findings support the conclusion that a great majority of our largest police agencies do have a polygraph screening program in effect. These agencies employ, on average, 447 officers and service a population averaging 522,000 citizens. They primarily use the polygraph to screen applicants for sworn positions; although, 54% also screen persons interested in non-sworn positions. Approximately 25% of the persons tested are disqualified from police employment based on the information developed during polygraph testing which, by the way, is used both to verify information provided in an application form and to develop information that cannot be uncovered by other means. Only a very small proportion (2%) of agencies use polygraph testing as a substitute for a background investigation. A rank ordered listing of topics covered during polygraph testing revealed that investigation of illegal drug usage, employment related dishonesty, and involvement in felonies are the most important.

When asked to indicate what their reasons were for using polygraph screening, the great majority of the agencies indicated that it reveals information that cannot be obtained by other means. Closely following was the belief that polygraph testing makes it easier to establish background information, it deters undesirable applicants, and it is faster than other methods of selection. The three leading benefits of polygraph screening were that applications were more honestly completed; higher quality employees were hired; and there were fewer undesirable employees. Over 90% of these agencies expressed either moderate or high confidence in their polygraph screening program, and 80% of them reported that, in their experience, the accuracy of the testing ranged between 86%-100%. The only procedure that was considered to be as useful as polygraph screening was a background investigation; all others, including written psychological tests, psychological or psychiatric interviews, personal interviews, and interviews by a selection board were judged to be less useful. Finally, this survey also showed that polygraph screening revealed applicant's involvement in serious, undetected criminality. For example, 9% of the agencies said that polygraph screening detected involvement by some applicants in unsolved homicides; 34% indicated some applicant involvement in forcible rape; and 38% showed some applicant participation in armed robberies. Other serious, unsolved crimes, such as burglary, arson and drug offenses were also revealed through polygraph screening.

Are there errors in a polygraph examination?

False positives, False negatives: While the polygraph technique is highly accurate, it is not infallible and errors do occur - as is the case with any test. Polygraph errors may be caused by the examiner's failure to properly prepare the examinee for the examination, or by a misreading of the physiological data on the polygraph charts. As with any test involving humans, it's possible for an examiner to do everything correctly and still have the test result in an error. Errors are usually referred to as either false positives or false negatives. A false positive occurs when a truthful examinee is reported as being deceptive; a false negative, when a deceptive examinee is reported as truthful. Since it is recognized that any error is damaging, examiners utilize a variety of procedures to identify the presence of factors which may cause errors or an unbiased review of the polygraph records.

Protective Procedures:

Examinee's Remedies: If a polygraph examinee believes that an error has been made, there are several actions that may be taken including the following:

Why do critics' accuracy figures vary?

One of the problems in discussing accuracy figures and the differences among the statistics quoted by proponents and opponents of polygraph techniques is the way the figures are calculated. At the risk of oversimplification, critics, who often don't understand polygraph testing, classify inconclusive test results as errors. In a real life setting an inconclusive result simply means the examiner is unable to render a definite diagnosis of truth or deception. In such cases a second examination is usually conducted at a later date.

To illustrate how the inclusion of inconclusive test results can distort accuracy figures, consider the following example: If 10 polygraph examinations are administered and the examiner is correct in 7 decisions, wrong in 1, and makes no decision as to truth or deception in 2 (inconclusive), we calculate the accuracy rate as 87.5% (8 definite results, 7 of which were correct). Critics of the polygraph technique often calculate the accuracy rate in this example as 70% (10 examination with 7 correct decisions). Since those who use polygraph testing do not consider inconclusive test results as meaningful and do not hold them against the examinee, considering them as errors is clearly misleading and certainly skews the figures.

Screening test accuracy: To date, there have been only a limited number of research projects on the accuracy of polygraph in screening contexts, primarily because of the difficulty in establishing ground truth in real world situations. However, since the same physiological measures are recorded and the same basic physiological principles may apply in both event-specific and screening examinations, there is little reason to believe that such testing is of no value in screening situations as some opponents claim. With that said, however, the number of issues, the lack of a known incident along with other factors likely result in lower average accuracies than seen in event-specific testing circumstances.

While no polygraph technique is infallible, research clearly indicates that when administered by a competent examiner who follows proper protocols, polygraph testing is one of the most accurate means available to determine truth and deception.

What is the scope of test questions?

In a law enforcement pre-employment polygraph examination, the questions include, but are not limited to, job related inquiries as the theft from previous employers, falsification of information on the job applications, the use of illegal drugs, and criminal activities. The test questions may be limited in the time span they cover, and all are reviewed and discussed with the examinee during a pre-test interview before any polygraph testing is done. There are no surprise or trick questions.

In a specific issue polygraph examination the relevant questions focus on the particular act under investigation.

Prohibitive Inquiries: Personal and intrusive questions have no place in a properly conducted polygraph examination. Many state licensing laws, the Employee Polygraph Protection Act, as well as the American Polygraph Association, have so stated in language similar to the following:


• religious beliefs or affiliations (unless specifically relevant to the job)

• beliefs or opinions regarding racial matters (except to the extent that any such biases could interfere with one’s ability to fairly and objectively perform his or her job)

• political beliefs or affiliations

• beliefs, affiliations or lawful activities regarding unions or labor organizations

• lawful sexual preferences or activities

Who gets the test results?

According to the various state licensing laws and the American Polygraph Association's Standards and Principles of Practice, polygraph results can be released only to authorized persons. Generally those individuals who can receive test results are the examinee and anyone specifically designated in writing by the examinee, the person, firm, corporation or governmental agency that requested the examination, and others as may be required by law.

What legislation applies to polygraph?

Licensing: Many states and some local jurisdictions have laws requiring licensure or certification for polygraph examiners. Most laws require formal instruction, an internship training period and successful completion of a licensing examination. For example, the following are basic requirements for licensure in one state:

A person is qualified to receive a license as an examiner:

• who establishes that he or she is a person of good moral character; and,

• who has passed an examination conducted by the Licensing Committee, or under its supervision. to determine his or her competency to obtain a license to practice as an examiner and

• who has conferred upon him or her an academic degree, at the baccalaureate level, from an accredited collect or university; and,

• who has satisfactorily completed 6 months of study in the detection of deception, as prescribed by rule.

Prohibitive Legislation: In addition to the Employee Polygraph Protection Act, to date there are several states and the District of Columbia that have enacted legislation designed to regulate an employer's use of the polygraph. No state prohibits polygraph testing in all settings. A typical statute states, “No employer may require a prospective or current employee to take a polygraph examination as a condition of employment or continued employment.” Most of these states make exceptions for testing of certain occupational groups. Commonly exempted are law enforcement agencies and companies that manufacture, distribute or dispense drugs and controlled substances.

The American Polygraph Association has consistently supported licensing efforts throughout the country. The APA encourages efforts to establish proper qualifications for polygraph examiners and criteria for testing procedures.

The Employee Polygraph Protection Act of 1988 (above) prohibits much, but not all pre-employment polygraph testing. Testing of employees is permitted to solve an employer's "economic loss." There are exemptions for guards, armored car personnel and those who handle drugs and narcotics. EPPA does not affect testing for attorneys or local, state or federal agencies. See: PL 199 437. Final Rules in the Federal Register, 56 (42). Monday, March 4 1991,29 CRF Part 801.


Polygraph admissibility varies from jurisdiction to jurisdiction. Some states ban it completely; others allow results by stipulation; and some allow polygraph evidence over objection.

Representative case citations are provided for reference:


Clements v. State, 474 So.2d 695 (1984).

Green v. Am. Cast Iron, 464 so.2d 294 (1984).


State v. Thomas Alexander / State v. James Griffith (download court decision)


State v. Valdez, 91 Ariz.. 274, 371, P.2d 894 (1962).

State v. Molina, 117 Ariz. 4541 573 P.2d 528 (App.1977).


Hays v. State, 767 S.W.2d 525 (1989).


People v. Houser, 85 Cal.App.2d 686, 193 P.2d 937 (1948)

Robinson v. Wilson, 44 Cal.App.3d 92, 118 Cal.Rptr. 569 (1974).

Witherspoon v. Superior Court, 133 Cal.App.3rd 24 (1982)


Williams v. State, 378 A.2nd 117 (1977).


State v. Chambers, 240 Ga. 76, 239 SE.2d 324 (1977).

Miller v. State, 380 S.E.2d 690 (1989).


State v. Fain, 774 P.2d 252 (1989).


Barnes v. State, 537 N.E.2d 489 (1989).

Davidson v. State, 558 N.E.2d 1077 (1990).


State v. McNamara, 104 N.W.2d 568 (1960).

Haldeman v. Total Petroleum, 376 N.W.2d 98 (1985).


State v. Roach, 570P.2d 1082 (1978).


Corbett v. State, 584 P.2d 704 (1978).

New Jersey:

State v. McDavitt, 297 A.2d 849 (1972).

State v. McMahon 524 A.2d 1348 (1986).

New Mexico:

State v. Dorsey, 539 P.2ed 204 (1975).

North Dakota:

State v. Newman, 409 N.W.2d 79 (1987).


Moss v. Nationwide, 493 N.E.2d 969 (1985).

State v. Souel, 372 N.E.2d 1318 (1978).


State v. Jenkins, 523 P.2d 1232 (1974).

State v. Rebetevano, 681 P.2d 1265 (1984).


State v. Grigsby, 647 P.2d 6 (1982).


Cullin v. State, 565 P.2d 445 (1977).



© 2010. American Polygraph Association | PO Box 8037, Chattanooga, TN 37414-0037 | (800) APA-8037

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