Assessing the Discrimination and Calibration of the Ontario Domestic Assault Risk Assessment in Switzerland

Intimate partner violence (IPV) is a major public health issue; worldwide, almost 1 in 3 women is affected. Police involvement in IPV cases has substantially increased because of “proarrest” and “procharging” policies and the enforcement of laws protecting victims of domestic violence. In the course of these changes, several front-line instruments have been developed to structure police risk assessment and decision-making strategies in such cases. One of those is the Ontario Domestic Assault Risk Assessment (ODARA). To investigate its validity in a Swiss police setting, a total cohort of male IPV offenders was retrospectively assessed for a fixed time at risk of 5 years. The recidivism base rate was 32% when recidivism was defined as subsequent police-registered IPV. Although ODARA scores were significantly correlated with IPV recidivism, they showed poor discrimination and calibration. Despite comparable base rates of recidivism, the Zurich sample scored significantly higher on the ODARA than the development sample. This mismatch of the expected and observed recidivism rates resulted in an overestimating of risk, especially in the two highest risk bins. Several reasons for those deviations, such as level of intervention, victim’s reporting behavior, and the dynamic nature of IPV, are discussed.