Replicating the Violence Risk Appraisal Guide: A Total Forensic Cohort Study

Rossegger, A., Endrass, J., Gerth, J., Urbaniok, F., & Singh, J. P. (2014). Replicating the Violence Risk Appraisal Guide: A total forensic cohort study. PLoS ONE, 9, e91845.

8 Pages Posted: 31 Jul 2014

See all articles by Astrid Rossegger

Astrid Rossegger

University of Konstanz - Department of Psychology

Jérôme Endrass

University of Konstanz - Department of Psychology

Juliane Gerth

University of Konstanz - Department of Psychology

Jay Singh

Høgskolen i Molde; Global Institute of Forensic Research

Date Written: 2014

Abstract

Introduction: The performance of violence risk assessment instruments can be primarily investigated by analysing two psychometric properties: discrimination and calibration. Although many studies have examined the discrimination capacity of the Violence Risk Appraisal Guide (VRAG) and other actuarial risk assessment tools, few have evaluated how well calibrated these instruments are. The aim of the present investigation was to replicate the development study of the VRAG in Europe including measurements of discrimination and calibration.

Method: Using a prospective study design, we assessed a total cohort of violent offenders in the Zurich Canton of Switzerland using the VRAG prior to discharge from prisons, secure facilities, and outpatient clinics. Assessors adhered strictly to the assessment protocol set out in the instrument’s manual. After controlling for attrition, 206 offenders were followed in the community for a fixed period of 7 years. We used charges and convictions for subsequent violent offenses as the outcomes. Receiver operating characteristic analysis was conducted to measure discrimination, and Sanders’ decomposition of the Brier score as well as Bayesian credible intervals were calculated to measure calibration.

Results: The discrimination of the VRAG’s risk bins was modest (area under the curve=0.72, 95% CI=0.63–0.81, p<0.05). However, the calibration of the tool was poor, with Sanders’ calibration score suggesting an average assessment error of 21% in the probabilistic estimates associated with each bin. The Bayesian credible intervals revealed that in five out of nine risk bins the intervals did not contain the expected risk rates.

Discussion: Measurement of the calibration validity of risk assessment instruments needs to be improved, as has been done with respect to discrimination. Additional replication studies that focus on the calibration of actuarial risk assessment instruments are needed. Meanwhile, we recommend caution when using the VRAG probabilistic risk estimates in practice.

Keywords: violence risk appraisal guide, risk assessment

Suggested Citation

Rossegger, Astrid and Endrass, Jérôme and Gerth, Juliane and Singh, Jay and Singh, Jay, Replicating the Violence Risk Appraisal Guide: A Total Forensic Cohort Study (2014). Rossegger, A., Endrass, J., Gerth, J., Urbaniok, F., & Singh, J. P. (2014). Replicating the Violence Risk Appraisal Guide: A total forensic cohort study. PLoS ONE, 9, e91845., Available at SSRN: https://ssrn.com/abstract=2473145

Astrid Rossegger

University of Konstanz - Department of Psychology ( email )

Konstanz, 78457
Germany

Jérôme Endrass (Contact Author)

University of Konstanz - Department of Psychology ( email )

Konstanz, 78457
Germany

Juliane Gerth

University of Konstanz - Department of Psychology ( email )

Konstanz, 78457
Germany

Jay Singh

Høgskolen i Molde ( email )

Molde NO-6405
Norway

Global Institute of Forensic Research ( email )

11700 Plaza America Drive
Suite 810
Reston, VA 20190
United States

HOME PAGE: http://www.gifrinc.com

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