Results from a Validation Study Comparing Ideographic and Nomothetic Risk Assessment Instruments

Abstract

During the judicial process there are several decision points which require an assessment of recidivism risk: e.g. decisions regarding sentence severity or the form of detention (i.e. low or high security unit), level of treatment, or decisions regarding transfers to open correctional facilities or release. Psychiatric experts called on by the court are required to not only assess recidivism risk, but also state if risk may be lowered by forensic psychotherapy. In the case of treated sex and violent offenders treatment progress has to be evaluated by the therapist and by external experts, before an offender will be released from a correctional institution. When considering the variety of available risk assessment instruments the question arises, which instrument is most suited for decision making. For instance, the “value” of an instrument can be determined by its validity for a specific target population, and by its validity for a specific outcome: Is the instrument valid for a specific offender population or judicial or correctional setting? For what kind of outcome criterion has the instrument been developed and validated?