Thursday, July 8, 2010

Polygraph Tests

Polygraph tests, commonly known as “lie detector” tests are becoming increasingly more popular in Ireland, but what is a polygraph test and in what circumstances are you likely to require one?

Polygraph Tests

The polygraph, which is in effect a medical instrument works by tracing changes in a person's physiological conditioning – changes in the autonomic nervous system- during questioning. These changes are recorded directly on to the polygraph charts so that they can be reviewed.
A polygraph examination usually takes between two and three hours from beginning to end, and consists of three different phases; pre-test interview, collection of charts, and analysis of charts.

The first part, the pre test interview, usually takes the longest time to complete. During this stage the examiner will explain how the polygraph works. He will then discuss the specific issue and develop and review all the questions to be asked on the polygraph test.

The subject is then attached to the polygraph. The set of questions, which was developed during the pre-test interview, will be asked three or four times. During this stage only the examiner and subject will be present.

Once the examiner has collected the charts he will review and analyse the results before giving a decision as to the subject's truthfulness or deception

How accurate are Polygraph Tests?

It is estimated that when carried out by a person who has been properly trained using a validated technique, the results are between 95% and 95% accurate. Polygraph test are an established fool proof way of establishing whether a person is being deceptive.

Is it possible to “beat” the polygraph?

If a person engages in behaviors in order to distort the polygraph tracings, it becomes evident to a trained examiner
Beating the polygraph," says Dr Louis Rovner, a noted scientist and polygraph expert in Los Angeles, California "is impossible for just about everybody." The polygraph is a scientific instrument which records physiological changes in our bodies. Polygraph examiners are trained to look for subtle abnormalities in these changes as a person answers a series of questions. The changes, he says, are involuntary reactions that occur in our bodies when we are not being truthful. "In order to beat the test," he says, "a person must use his central nervous system to override the involuntary activity of the autonomic nervous system, and he must do it on cue, every 25 seconds or so." Given the anxiety of a typical polygraph subject, it is extremely unlikely that anyone could successfully fool a competent polygraph examiner.

In what circumstances are Polygraph tests used?

There are a wide range of scenario’s where polygraph tests have been used. Annie Murphy of Bluemoon Investigations comments that Bluemoon clients have requested polygraph tests relating to marital infidelity, fraud, theft, pre-employment screening, family disputes, domestic abuse and truth verification.
Polygraphs can also be used where accusations of sexual abuse have been made. In fact the U.K Probation services in nine areas are taking part in a three year trial of polygraph session on sex offenders. Paedophiles and rapists are having to take lie-detector tests in a bid to stop them re-offending. They must take regular tests as a condition of their release from prison and could be sent back to custody if they refuse as a breach of parole.


In most European jurisdictions, polygraphs are not generally used by police forces. However, in any lawsuit, an involved party can order a psychologist to write an opinion based on polygraph results to substantiate the credibility of its claims. The court weighs the opinion like any other opinion the party has ordered. In most cases, polygraph tests are voluntarily taken by a defendant in order to substantiate his or her claims.

If you would like to arrange a Polygraph Test please contact Annie Murphy at Bluemoon Investigations.

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