Research Summary: Dynamic Risk Scales Decay Over Time: Evidence for Reassessment
Given the accuracy of risk tools degrades over time, regular reassessment of dynamic risk scales (STABLE-2007 and ACUTE-2007) assists corrections officers in evaluating individuals’ risk more accurately. Acute tools benefit from being reassessed more frequently than stable tools.
Many forensic evaluators (e.g., psychologists, psychiatrists) and community supervision officers routinely use dynamic risk assessment tools to determine the reoffending risk of justice-involved individuals and also to make effective intervention plans to reduce the likelihood of reoffending.
Dynamic risk tools include risk factors that are amenable to change or intervention, such as antisocial tendencies. The items measured within a dynamic assessment can help identify the characteristics of an individual that are conducive to change and that, when targeted, can reduce their overall risk of reoffending.
Dynamic risk factors can be further defined as being stable or acute. Stable dynamic risk factors are durable, changing infrequently over months to years (for example, problem-solving abilities). Acute dynamic risk factors are those that change quickly, over minutes to days (for example, access to victims).
The ACUTE-2007 and STABLE-2007 (Hanson et al., 2007) are two dynamic tools designed to assess the likelihood of sexual recidivism. Both the ACUTE-2007 and STABLE-2007 are widely used by correctional officers, forensic experts, and mental health practitioners (Bourgon et al., 2018; Kelley et al., 2020).
Although developers of dynamic risk tools recommend regular reassessments, there is little research examining the extent to which the predictive accuracy of dynamic risk assessments decays over time (i.e., how often reassessments of dynamic risk should be conducted for optimal predictive accuracy).
This study investigated how the predictive accuracy of two popular dynamic risk assessment tools for sexual reoffending, the ACUTE-2007 and the STABLE-2007, determine the decay rate of these measures after specific periods have elapsed (e.g., 30 days, 45 days, 60 days, 120 days, or 180 daysprior to recidivism).
The present research included two independent studies:
- Study 1 (N = 795) with the developmental sample (i.e., the Dynamic Supervision Project [Hanson et al., 2007]) of men undergoing community supervision across all Canadian provinces and territories, and the Atlantic Region of the CSC and that was used to develop the ACUTE-2007 and STABLE-2007 tools. The average length of follow-up was 6.5 years (SD = 2.6, ranging from 0.1 to 10.1 years). The sample had a total of 6,656 ACUTE-2007 and 1,243 STABLE-2007 assessments.
- Study 2 (N = 4,221) included men undergoing community supervision from British Columbia Corrections. The average length of follow-up was 4.6 years (SD = 2.5, ranging from 0.1 to 8.5 years). During the follow-up time, the sample had a total of 56,091 ACUTE-2007 assessments and 11,101 STABLE-2007 assessments.
Across the samples, we found that regular reassessments using dynamic risk tools (STABLE-2007 & ACUTE-2007) improved the prediction of recidivism risk compared to using their first score on the tool. We also found that the more recent an assessment is (i.e., closer proximity), the better the predictive accuracy.
The predictive accuracy of the ACUTE-2007 scores declined more quickly and more obviously than STABLE-2007 scores. This pattern would be expected given that ACUTE-2007 is intended to assess rapidly changing features, whereas stable dynamic factors are conceptualized as relatively enduring qualities.
A potential limitation of this study is that the current samples received provincial community supervision sentences in Canada may not be representative of other individuals who received federal sentences in Canada. In addition, individuals who commit different types of sexual crimes (e.g., rapists vs. child molesters) might show different decay rates of the predictive accuracy of dynamic risk tools.
For the most accurate assessment of risk, reassessments using the ACUTE-2007 should occur at every meeting with supervisees (e.g., probationers, parolees) or at least every 30 days during the community supervision. For STABLE-2007, current results support reassessment every six months. Given that updating scores of STABLE-2007 requires more extensive effort (e.g., interview and review of file information), however, the decision about when to update the STABLE-2007 needs to balance increasing predictive accuracy for more recent assessment against the cost of new assessments.
Lee, S. C., Babchishin, K. M., Mularczyk, K. P., & Hanson, R. K. (2021). Dynamic risk scales decay over time: Evidence for reassessment. Public Safety Research Report. 2023-R003.
Hanson, R. K., Harris, A., Scott, T., & Helmus, L. (2007). Assessing the risk of sexual offenders on community supervision: The Dynamic Supervision Project (Corrections Research User Rep. No. 2007-05). Public Safety Canada.
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Research Summaries are produced for the Crime Prevention Branch, Public Safety Canada. The summary herein reflects interpretations of the report authors’ findings and do not necessarily reflect those of the Department of Public Safety Canada.
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