Polygraph: The Use of Polygraphy in the Assessment and Treatment of Sex Offenders in the UK

Abstract

The polygraph is often described as a lie detector. Its use is based on the notion that lying induces a 'stress response' in the automatic nervous system, a part of the Central Nervous System that is largely outside conscious control and which regulates the body's internal environment. The effect of this can be observed in changes in cardiovascular activity, breathing, and sweating. The basis of the polygraph examination involves individuals being asked a series of questions while activity in these systems is recorded, with certain reactions said to be indicative of deception. A definitive review carried out by the National Research Council (2003) in the United States concluded that the accuracy of polygraph testing is likely to be in the region of 80 – 90%. HISTORY AND RESEARCH A large trial of Post Conviction Sex Offender Testing (PCSOT) in England involving sex offenders managed by the probation service took place between 2003 and 2005 (Grubin, 2006). In this study, polygraphy was introduced on a voluntary basis to sex offenders taking part in programmes in 10 probation areas, with polygraphed offenders compared with 180 sex offenders in four probation areas where polygraphy was not introduced. Over two years, 347 sex offenders attended for testing. Feedback from probation officers was received in respect of 68% of all the tests that were carried out. In brief, probation officers reported that new disclosures relevant to treatment or supervision were made in 70% of first tests, compared with 14% of non-polygraphed offenders making similar disclosures over the previous six months. The disclosures made by polygraphed offenders were rated as 'medium,' severity (that is, relating to behaviours indicative of increased risk) or 'high' (actual breaches or offences) in over 40% of cases. The odds of a polygraphed offender making a disclosure relevant to his treatment or supervision were 14 times greater than they were for non-polygraphed ones. When probation officers were asked about the impact of testing on treatment and supervision, polygraphy was rated as being 'somewhat' or 'very' helpful in over 90% of cases.