Should Lie-Detector Tests Be Used To Monitor Convicted Sex Offenders?

Main Category: Psychology / Psychiatry
Article Date: 09 Aug 2008 - 4:00 PDT

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In the September edition of Legal and Criminological Psychology, Forensic Psychiatrist Professor Don Grubin and Professor Gershon Ben-Shakhar argue the cases for and against the use of polygraph testing of convicted sex offenders.

Polygraph, or lie detector tests, monitor physiological responses such as heart rate. Individual's physiological responses to questions are measured and the polygraph records the body's responses that reflect psychological stress and arousal. In the case of convicted sex offenders, offender's responses to questions such as their use of pornography or whether they have been on the lookout for victims are measured, with the aim of monitoring behaviour and adherence to relapse prevention plans.

Polygraph testing is widely used with convicted sex offenders in the United States to assist in their treatment and supervision, and in 2007 legislation was passed in England enabling a national trial of mandatory testing in the probation service.

In the journal Legal & Criminological Psychology, Professor Don Grubin from Newcastle University and the Northumberland, Tyne and Wear NHS Trust puts forward the case for post-conviction sex offender testing (PCSOT).

He claims: "The focus of PCSOT is facilitating disclosure to assist in the treatment and supervision of sex offenders. PCOST has been found to be effective at getting a complete sexual history, checking compliance with treatment and supervision and gaining information about an individual's offending."

However Professor Gershon Ben-Shakhar (Hebrew University of Jerusalem) believes: "Polygraph examinations have no value as a scientific method for detecting deception and uncovering information the examinee does not wish to disclose." Arguing that "autonomic measures are by no means measures of deception".

Furthermore, he claims that as the measurement of these physiological responses lacks standardization, the results cannot be quantified objectively so 'pass' and 'fail' are subjective judgements vulnerable to several biases.

The full cases for and against the use of polygraph testing of sex offenders can be found in Legal and Criminological Psychology, Volume 13 Part 2 September 2008.

The British Psychological Society

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