Journal of Forensic Psychology Practice, 10:360–371, 2010 Copyright © Taylor & Francis Group, LLC ISSN: 1522-8932 print/1522-9092 online DOI: 10.1080/15228932.2010.481244 PRACTICE UPDATE Individualizing Risk Assessment: Balancing Idiographic and Nomothetic Data DAVID DEMATTEO, JD, PhD, ASHLEY BATASTINI, BS, ELIZABETH FOSTER, BA, and ELIZABETH HUNT, BS Department of Psychology, Drexel University, Philadelphia, Pennsylvania Forensic mental health professionals are conducting risk assess- ment evaluations with increasing frequency in a variety of crimi- nal, civil, and family law contexts. Although evaluators can choose from a variety of empirically validated risk assessment tools, there is comparatively little guidance on how data gathered during the evaluation should be utilized in reaching the final risk deter- mination. In particular, research suggests that evaluators find it challenging to balance nomothetic and idiographic data in risk assessment contexts. After highlighting several errors involving the use of nomothetic and idiographic data, we offer guidance for achieving an effective balance between both sources of data. KEYWORDS risk assessment, idiographic, nomothetic, forensic mental health assessments INTRODUCTION Over the past 20 years, the knowledge base regarding violence risk assess- ment has burgeoned within the field of forensic psychology. As a result, forensic mental health professionals are conducting risk assessments with increasing regularity (Conroy & Murrie, 2007). These risk assessments can differ in content (e.g., assessment of violence risk versus sexual risk) and may be conducted with different populations (e.g., juveniles versus adults) in criminal, civil, and family law contexts. For example, forensic mental Address correspondence to David DeMatteo, Department of Psychology, Drexel University, MS 626, 1505 Race Street, Philadelphia, PA 19102. E-mail: dsd25@drexel.edu 360