Polygraph or Lie Detector Testing

Lie Detection Methods in the Criminal, Private and Security Sector

Feb 4, 2008 Karen Lotter

Polygraphs or lie detectors are most often associated with criminal investigations, but they are also used in the private sector under strict guidelines.

What is a Polygraph or Lie Detector Test?

A polygraph is also often referred to as a lie detector. The underlying theory of the polygraph is that when people lie they also get measurably nervous about lying.

The Polygraph instrument measures and records several physiological responses like blood pressure, pulse, respiration and electro-dermal response while the subject answers a series of questions.

The term "polygraph" literally means "many writings."

Within the Federal Government, a polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination.

The Polygraph Testing or Lie Detection Procedure

Polygraph examiners, also known as forensic psychophysiologists, may use analog instruments or newer computerized polygraph instruments for their tests.

A polygraph instrument will collect physiological data from at least three systems in the human body. A typical polygraph test will include a period referred to as:

a pre-test,
a chart collection phase, and
a test data analysis phase.

Experience and Training is Important for Forensic Psychophysiologists

Lie detectors do not, as their name suggests, detect lies. They can only detect whether deceptive behavior is being displayed.

Polygraph examiners look for significant involuntary responses going on in a person's body when that person is subjected to stress – usually the stress associated with deception. That will reflect in the polygraph test.

Fluctuations could indicate that person is being deceptive, but polygraph exam results are open to interpretation by the examiner. If the forensic psychophysiologist is properly trained and has the experience, he/she can interpret the results of the polygraph test to a high level of accuracy.

Accuracy of Polygraph Testing

One of the problems in discussing accuracy figures and the differences between the statistics quoted by proponents and opponents of the polygraph technique is the way that the figures are calculated. Add them one way, and the results are positive; the other and the results are negative.

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 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 of "low quality."

But the American Polygraph Association claims that while the polygraph test technique is not infallible, research clearly indicates that when administered by a competent examiner, the polygraph test is one of the most accurate means available to determine truth and deception.

The American Polygraph Association (APA)

The American Polygraph Association (APA) was organized in 1966 as a coalition of polygraph professionals, researchers, and instrumentation developers. The American Polygraph Association (APA) is the leading professional polygraph organization in the world, representing more then 3,200 experienced polygraph examiners in private business, law enforcement and government.

What is EPPA?

The American Civil Liberties Union strongly supported the passage of the Employee Polygraph Protection Act of 1988 (EPPA) which outlaws the use of the polygraph "for the purpose of rendering a diagnostic opinion regarding the honesty or dishonesty of an individual." On December 27, 1988, the Employee Polygraph Protection Act (EPPA) became law. This federal law in the USA established guidelines for polygraph testing and imposed restriction on most private employers.

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 a polygraph test in court testimony remains controversial, although it is used extensively in post-conviction supervision, particularly of sex offenders.
In most European jurisdictions, polygraphs are not considered reliable evidence and are not generally used by police forces.
In Canada, the use of a polygraph is sometimes employed in screening employees for government organizations.

The European Polygraph Association (EPA) promotes and impels the use and development of the polygraph technique in Europe while the British Polygrpah Assocation (BPA) serves the sme purpose in Britain.

Sources:

The American Polygraph Association

Polygraph Policy –Project on Government Secrecy – Federation of American Scientists

The Polygraph Place

The copyright of the article Polygraph or Lie Detector Testing in Forensic Science is owned by Karen Lotter. Permission to republish Polygraph or Lie Detector Testing in print or online must be granted by the author in writing.

Digital Lie detector - Lafayette Instrument.

Polygraph Instrument.

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Dec 2, 2008 9:18 PM

Guest :

these tests cause more innocent people to be put in jail

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