Penile Plethysmograph Tests (Hansard, 10 July 1995)

§ Miss Widdecombe

Responsibility for this matter has been delegated to the Director General of the Prison Service, who has been asked to arrange for a reply to be given.

Letter from Derek Lewis to Mr. George Howarth, dated 10 July 1995: The Home Secretary has asked me to reply to your recent Question about what assessment has been made of the accuracy of penile plethysmograph (PPG) tests as predictions of behaviour; what are the guidelines for use of such tests; and what assessments has been made of the consequences of taking such tests in terms of prisoners' assumptions about one another. The use of PPG by the Prison Service follows the guidelines published by the British Psychological Society and is only one element in the comprehensive assessment which forms part of the Prison Service's Sex Offender Treatment Programme (SOTP). Its use is based on relevant research findings and advice from international experts. This research indicates that sadistic and paedophilic sexual preferences, shown up by the PPG, are common among convicted sex offenders and rare among unconvicted men. In addition, convicted sex offenders, who show these preferences to a more marked degree appear more likely to re-offend. However, PPG assessment is not primarily used by the Prison Service to predict future behaviour. It is used with men who have already been identified as being at risk of committing sexual offences to assess one factor, sexual preferences, which may contribute to their offending. Since the PPG is used as part of a comprehensive package of assessment and treatment, it is difficult to isolate this particular element from the effect of the SOTP as a whole. Research has shown, however, that by the end of the SOTP, when PPG assessment is included, participants typically:

accept responsibility for their offences rather than blaming other people.
are more aware of the damage and distress caused to victims.
are more aware of the factors which put them at risk of committing further offences.
have worked out ways of controlling these factors.
behave in a less aggressive and impulsive way in relation to prison staff and other prisoners.
are less emotional and angry.

A careful and rigorous evaluation of its effects on prisoners is built into the SOTP. The programme is periodically revised in the light of evaluation results.