Polygraph Tests and Lie Detectors

Learn about polygraphs and lie detector tests.

What is a Polygraph Test?

A polygraph test (commonly referred to as a lie detector test) is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration, and skin conductivity while the subject is asked and answers a series of questions, on the basis that false answers will produce distinctive measurements.

Within the U.S. federal government, a polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination. Several other technologies are also used in the field of lie detection, but the polygraph is the most famous.

Polygraph Machines

The polygraph machine measures physiological changes caused by the sympathetic nervous system during questioning.

Many people wonder if lie detector tests are accurate and reliable. The is no proof that certain physiological reactions mean that a person is lying or being deceptive. For example, an honest person may simply be nervous during a test, which would affect the results. In contrast, a dishonest person may know how to control their emotions and beat the test.

Another common myth is that polygraph testing is used in every investigation. In reality, the tests are rarely used because the results aren’t always admissible in court. Courts are not required to allow lie detector test results as evidence. Individual judges have the authority to decide whether the results can be used.

Polygraph Test Resources

The following are resources for polygraphs, testing, and related resources.

American Polygraph Association – The largest organization for truth verification specialists in the world. Represents the interests of examiners in government, law enforcement, and private business. Provides access to helpful resources, publications, and training resources.

Federation of American Scientists: Polygraph Policy – An extensive list of official documents, articles, and other resources on polygraph testing.

How to Pass a Polygraph Test – Prepare to pass the test by knowing how to always produce a truthful chart. Almost half of the time, if you’re nervous when you take the test, you’ll end up being branded as a liar. This is why the tests are often inadmissible because it is not a true lie detection test.

National Polygraph Association – Organization whose goal is to promote and advance public acceptance of the polygraph and to urge the members’ active participation in civic and community affairs where the polygraph is concerned. Includes helpful resources links and tools and allows you to search for a certified examiner. It also provides membership for existing examiners.

Polygraph Evidence in Court – Examining lie detection results as a sensible approach to the problem of wrongful convictions due to perjury by police, jailhouse informants, and co-operating prosecution witnesses. A somewhat helpful website yet contains a lot of text, long pages, and a lot of links. It may take you a while to sift through to find what you need.

Hire a Private Investigator to Help

Some private investigators offer polygraph examination services. Visit our Private Investigator Directory to find a polygraph examination provider in your area.

Questions and Comments

If you have any questions about polygraph machines or polygraph tests, please post a message below.

Michael Kissiah is the owner of Brandy Lane Publishing, LLC, which owns and operates a small portfolio of websites, including eInvestigator.com. Michael created eInvestigator.com more than 20 years ago after working as a private investigator in the state of Florida. Since that time, he has become an expert at how to find information online and has written over 1000 articles on topics related to the investigation industry. In addition, he is the author of the "Private Investigator Licensing Handbook", available at Amazon.com.


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