STABLE-2007 and ACUTE-2007

Sexual offenders do great societal damage that causes justifiable public concern. Over the past 10 years, psychology has developed the ability to reliably classify male sexual offenders as low, moderate, and high risk for sexual recidivism (Minnesota Sex Offender Screening Tool-Revised, Risk Matrix-2000, Rapid Risk Assessment for Sexual Offense Recidivism, and STATIC-99) based on historical, static, nonchangeable risk factors. The “static” structure of these tests effectively precludes their ability to measure changes in risk. The STABLE-2007 and the ACUTE-2007 instruments are specialized tools designed to assess and track changes in risk status over time by assessing changeable “dynamic” risk factors. “Stable” dynamic risk factors are personal skill deficits, predilections, and learned behaviors that correlate with sexual recidivism but that can be changed through a process of “effortful intervention” (i.e., treatment or supervision). Should such intervention take place in such a way as to reduce these risk-relevant factors, there would be a concomitant reduction in the likelihood of sexual recidivism. “Acute” dynamic risk factors are highly transient conditions that only last hours or days. These factors are rapidly changing environmental and intrapersonal stresses, conditions, or events that have been shown by previous research to be related to imminent sexual re-offense. These instruments should be used to inform correctional managers as to how much risk they are managing, inform decisions on levels of communitytreatment and supervision, and estimate changes in risk status pre- and posttreatment or other interventions.

In the late 1990s, Karl Hanson and Andrew Harris began to investigate the relationship between sexual recidivism and dynamic, changeable, risk factors that correlated with sexual recidivism. This work produced the Sex Offender Needs Assessment Rating (SONAR) assessment, which demonstrated adequate internal consistency and a moderate ability to differentiate sexual recidivists from nonrecidivists. Extending this work, Hanson and Harris broke the SONAR into two parts, creating a stable measure of dynamic risk, STABLE-2000 (16 items), and an acute measure of dynamic risk, ACUTE-2000 (8 items).

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To test these new instruments, Hanson and Harris instituted a prospective study, the Dynamic Supervision Project, involving every Canadian province and territory and the states of Alaska and Iowa in a robust test of risk assessment methodologies. A total of 156 parole and probation officers completed repeated three-level (static, stable, and acute) risk assessments on 997 sexual offenders across 16 jurisdictions. All the probation and parole officers scoring risk of re-offense for these community-based sexual offenders were trained in sexual offender risk assessment by attending a 2-day training that focused on scoring actual case examples. Sexual, violent, and “other” recidivism information was gathered from official criminal histories after a median of 41 months of follow-up. Results showed that both STABLE-2000 and ACUTE-2000 added predictive validity above that demonstrated by STATIC-99 alone. The sexual recidivism rate for this widely disparate group of community-based sexual offenders was 7.6% after 3 years (n = 790). Empirically based changes in scoring were recommended, and this research led to the development of two improved dynamic risk measures, the STABLE-2007 and ACUTE-2007 instruments.

STABLE-2007 assesses 13 stable risk factors that have been shown to correlate with sexual recidivism: significant social influences, capacity for relationship stability, emotional identification with children, hostility toward women, general social rejection, lack of concern for others, impulsivity, poor problem-solving skills, negative emotionality, sex drive and preoccupations, sex as coping, deviant sexual preference, and cooperation with supervision. Each of these 13 items are scored on a 3-point scale (0 = no problem evident, 1 = some problem evident, and 2 = significant problem evident) for a total of 26 possible points. Emotional identification with children is not scored for those offenders who do not have a child victim, and the scale is subsequently scored out of 24 points for that group. The offender’s STATIC-99 score is then combined with his STABLE-2007 score to produce percentage estimates of sexual recidivism, sexual recidivism plus sexual breaches, violent recidivism, any criminal recidivism (breaches excluded), and any criminal recidivism including breaches at 1, 2, 3, and 4 years.

ACUTE-2007 assesses seven acute, rapidly changing risk factors that correlate with sexual recidivism. In this scale, there are two factors. The first factor predicts sexual and violent reoffending and uses the following four risk factors: victim access, hostility, sexual preoccupation, and rejection of supervision. The second factor predicts general criminal recidivism using the aforementioned four factors plus emotional collapse, collapse of social supports, and substance abuse for a total of seven items. Each of these seven items is scored on a 4-point scale (0 = no problem evident, 1 = some problem evident, 2 = significant problem evident, and IN = intervene now) for a total of 14 possible points. An “Intervene Now” score calls for immediate intervention to prevent imminent re-offense or supervision catastrophes such as suicide. Once ACUTE-2007 has been scored, this outcome is combined with the offender’s STATIC-99/ STABLE-2007 score to estimate an overall risk priority. The offender is nominally classified as a low, moderate, or high risk for sexual and violent recidivism and as a low, moderate, or high risk for general criminal recidivism. Appropriate, empirically based risk ratios can then be applied to determine intervention priority.

The STABLE-2007 and the ACUTE-2007 instruments are easier to score than their predecessors, and combinations of the STATIC-99 and STABLE-2007 instruments produced receiver operating characteristic (ROC) curve values for sexual re-offense commonly in the 0.76 range. When used by “conscientious” officers, the STATIC-99/STABLE-2007 combined scores produced an ROC for sexual re-offense of 0.84 and 0.80 for violent recidivism. STABLE-2007 and ACUTE-2007 assessments were found to add predictive power above and beyond that available to assessments of static risk alone.

This study provides further evidence that trained community supervision officers can reliably score valid and useful sex offender risk assessments. Results of this nature, even taking into account the need for replication and cross-validation, suggest significant policy and practice implications for the community supervision of sexual offenders. The STABLE-2007 and the ACUTE-2007 instruments have demonstrated predictive validity beyond that of the SONAR and the STABLE-2000/ACUTE-2000 packages. STABLE-2007 and ACUTE 2007 are available free of charge from the authors. The authors no longer support or recommend the use of SONAR, STABLE-2000, or ACUTE-2000 but recommend STABLE-2007 and ACUTE-2007 for assessing dynamic changes in risk for sexual offenders.


  • Hanson, R. K., Harris, A. J. R., Scott, T.-L., & Helmus, L. (2007). Assessing the risk of sexual offenders on community supervision: The Dynamic Supervision Project (User report, Corrections research). Ottawa, ON, Canada: Public Safety Canada. Retrieved from

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