The term “polygraph” means “many writings,” referring to how it records multiple physiological responses simultaneously. Polygraph examiners use either conventional analog instruments or computerized systems to conduct examinations.
A polygraph collects physiological data from three key areas of the human body:
- Respiratory Activity: Measured by rubber tubes placed around the chest and abdomen.
- Sweat Gland Activity: Recorded using metal plates attached to the fingers.
- Cardiovascular Activity: Monitored through a blood pressure cuff or similar device.
A standard polygraph test includes the following phases:
- Pre-Test: The examiner reviews paperwork, discusses the test process, and goes over the questions with the examinee.
- Chart Collection: The examiner administers the test and records physiological responses.
- Analysis: After the test, the examiner reviews the charts and provides an opinion on the examinee’s truthfulness.
The examiner may also allow the examinee to explain any unusual physiological responses to specific questions.
It’s important to note that instruments claiming to measure “voice stress” are not polygraphs and lack scientific validation.
Who Uses Polygraph Examinations?
Polygraph examinations are used in three main sectors of society:
- Law Enforcement Agencies
- Federal, state, and local police and sheriff’s departments.
- Legal Community
- U.S. Attorney Offices, District Attorney Offices, Public Defenders, Defense Attorneys, and Parole or Probation Departments.
- Private Sector
- Companies and corporations, within the limitations of the Employee Polygraph Protection Act (EPPA) of 1988.
- Private citizens for personal matters outside the legal system.
Public Service Warning
There is a growing trend of polygraph con artists exploiting unsuspecting clients. To avoid falling victim to fraud, take time to verify the credibility of polygraph service providers.
Accuracy and Criticism
Discussions on polygraph accuracy often vary due to how results are calculated. Critics may classify inconclusive results as errors, while proponents do not.
For example:
- In a test of 10 examinations, if 7 results are correct, 1 is incorrect, and 2 are inconclusive:
- Critics calculate accuracy as 70% (7/10).
- Proponents calculate accuracy as 87.5% (7 correct out of 8 definitive results).
Inconclusive results simply mean the examiner cannot render a definitive diagnosis. A retest is typically conducted.
When conducted by a qualified examiner, polygraph tests are among the most reliable methods for determining truth and deception.
Pre-Employment Testing
Limited studies on pre-employment polygraph testing show accuracy rates consistent with other polygraph uses. Polygraphs are highly effective for screening job applicants, especially in law enforcement.
The Employee Polygraph Protection Act (EPPA) restricts private employers from using polygraphs for pre-employment screening, but public employers, such as police agencies, are exempt.
Errors in Polygraph Examinations
Errors, while rare, can occur and are categorized as:
- False Positives: Truthful individuals mistakenly identified as deceptive.
- False Negatives: Deceptive individuals mistakenly identified as truthful.
Examiners take steps to minimize errors, including:
- Assessing the examinee’s emotional and physical state.
- Conducting pre-test interviews and reviewing questions thoroughly.
- Performing quality control reviews of the charts.
Scope of Questions
Polygraph tests avoid intrusive or irrelevant questions, such as those about:
- Religion, race, or political affiliations.
- Union activities or sexual preferences.
Pre-employment tests focus on job-related topics, like drug use, honesty on applications, or criminal behavior. Questions are discussed in advance with the examinee, and no surprises are allowed during the test.
Who Receives Test Results?
Polygraph results are confidential and released only to authorized individuals, such as:
- The examinee or their authorized representatives.
- The person or entity requesting the test.
Results may also be disclosed as required by law.
Conclusion
The polygraph technique, while not infallible, remains one of the most accurate tools for detecting truth and deception when performed by a competent examiner. By following strict ethical guidelines and maintaining high professional standards, polygraph examiners continue to provide valuable services to law enforcement, legal professionals, and private individuals alike.
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