Impact evaluation of the prison-based Core Sex Offender Treatment Programme

Published: Jun 2017

Ministry of Justice: Aidan Mews, Laura Di Bella and Mark Purver

The main findings of the analysis were as follows:

Some statistically significant differences were detected over an average 8.2 year follow up period.They were small in magnitude although they widened over the follow-up period. In particular:

  • More treated sex offenders committed at least one sexual reoffence (excluding breach) during the follow-up period when compared with the matched comparison offenders (10.0% compared with 8.0%).
  • More treated sex offenders committed at least one child image reoffence during the follow -up period when compared with the matched comparison offenders (4.4% compared with 2.9 %). Otherwise, the matched treated and comparison groups had similar reoffending rates across a variety of outcome measures.

A variety of sensitivity analyses were performed, which mostly focused on the sexual reoffending measure. The sexual reoffending treatment effect was found to be reasonably stable across these.