Identifying change in the likelihood of violent recidivism: causal dynamic risk factors in the OASys violence predictor.

Recent studies of multiwave risk assessment have investigated the association between changes in risk factors and violent recidivism. This study analyzed a large multiwave data set of English and Welsh offenders (N = 196,493), assessed in realistic correctional conditions using the static/dynamic Offender Assessment System (OASys). It aimed to compare the predictive validity of the OASys Violence Predictor (OVP) under mandated repeated assessment and one-time initial assessment conditions. Scores on 5 of OVP's 7 purportedly dynamic risk factors changed in 6 to 15% of pairs of successive assessments, whereas the other 2 seldom changed. Violent reoffenders had higher initial total and dynamic OVP scores than nonreoffenders, yet nonreoffenders' dynamic scores fell by significantly more between initial and final assessment. OVP scores from the current assessment achieved greater predictive validity than those from the initial assessment. Cox regression models showed that, for total OVP scores and most risk factors, both the initial score and the change in score from initial to current assessment significantly predicted reoffending. These results consistently showed that OVP includes several causal dynamic risk factors for violent recidivism, which can be measured reliably in operational settings. This adds to the evidence base that links changes in risk factors to changes in future reoffending risk and links the use of repeated assessments to incremental improvements in predictive validity. Further research could quantify the costs and benefits of reassessment in correctional practice, study associations between treatment and dynamic risk factors, and separate the effects of improvements and deteriorations in dynamic risk.