Validation of an Actuarial Instrument to Predict Repeat Family Violence for Frontline Police: Calibration, Discrimination and Classification Performance of the VP-SAFvR

Police are increasingly tasked with identifying, responding to, and preventing intimate partner and family violence (IPFV). Several police organisations have adopted validated risk assessment instruments to assist frontline police officers to assess and manage the risk of future IPFV. This paper reports a population-based evaluation of the predictive and discriminative validity of an actuarial risk assessment instrument, the Victoria Police Screening Assessment for Family Violence Risk (VP-SAFvR), used by frontline police officers in Victoria, Australia.

The entire population (n = 38,454) of family violence reports (FVRs) where police used the VP-SAFvR between 1 September 2019 and 31 March 2020 were tracked for 365 days to ascertain whether the VP-SAFvR was able to predict subsequent family violence and discriminate between cases with and without subsequent family violence. Calibration and survival analysis was performed on the instrument.

Approximately 33% of the sample was involved in subsequent IPFV over the 12 month outcome period. In line with the development (McEwan et al., 2019) and validation (Spivak et al., 2020) studies of the same instrument, the results show the VP-SAFvR continues to provide adequate consistent discriminative and predictive performance across time. The AUC for repeat IPFV was 0.65, with the recommended threshold score of 4 (or above) identifying 75% of individuals involved in repeat family violence and correctly screening out approximately 50% of non-repeat cases.

The paper extends the previous research on VP-SAFvR by providing some indication that the tool is well-calibrated. Incidence curves show the largest increase in repeat family violence among those scoring above threshold occurs in the first 90 days post index. The implications and limitations of the study are discussed.