Measuring the change in risk posed by sex offenders

Measuring the change in risk posed by sex offenders PDF Version (11KB)

Research summary
Vol. 5 No. 1
January 2000


How can we evaluate changes in risk levels for sex offenders?


New offences by known sex offenders invoke considerable concern among the public and the professionals responsible for supervising them. Preventing new offences requires accurate information concerning recidivism risk. Previous research has found that empirically based, structured approaches are generally more accurate that unstructured professional opinion. Although there are risk scales for assessing long-term risk potential, there are no established scales for evaluating change in risk levels among sex offenders.


The dynamic (changeable) risk factors identified in a previous study (Hanson & Harris, 1998) were organised into a structured assessment procedure. The Sex Offender Need Assessment Rating (SONAR) includes five relatively stable factors (intimacy deficits, negative social influences, attitudes tolerant of sex offending, sexual self-regulation, general self-regulation) and four acute factors (substance abuse, negative mood, anger, victim access). The stable factors were expected to endure for months or years, whereas the acute factors were expected to change over weeks or days.

The validity of the scale was examined using data previously collected on 208 sex offenders who had recidivated sexually while on community supervision and a comparison group of 201 sex offenders who had not reoffended.


Overall, the scale showed a moderate ability to differentiate between recidivists and non-recidivists. The recidivists displayed more problems than the non-recidivists on each of the areas targeted by the SONAR. The recidivists showed the greatest problems in their capacity to conform to the demands of community supervision, and lesser, although still substantial problems, in sexual self-regulation, attitudes tolerant of sexual offending, and negative peer associations. SONAR scores continued to distinguish between the recidivists and non-recidivists after controlling for other known risk indicators, such as age, IQ, and scores on established measures of long-term risk potential.

Policy implications

  1. Many applied risk decisions with sex offenders, such as treatment outcome and supervision on conditional release, can benefit from considering both static and dynamic risk factors.
  2. The scale constructed in this study is a promising approach to evaluating dynamic risk factors and changes in risk levels for sex offenders.
  3. Since the risk level of an individual offender can change substantially, policies should allow for the reintegration of sexual offenders into society and not assume that all those who have committed such offences are indefinitely at high risk to reoffend.


For further information

James Bonta, Ph.D.
Solicitor General Canada
340 Laurier Avenue West
Ottawa, Ontario
K1A 0P8
Tel (613) 991-2831
Fax (613) 990-8295

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