Purpose. Treatments and risk assessments determined by the offence paralleling behaviour (OPB) framework appear to have found a place in practice well ahead of empirical support and conceptual clarity. Although the framework is intuitively appealing its inappropriate use may have profound negative implications for patients. Incapacitation and unnecessary treatments may be demanded when observed behaviours are interpreted as evidence of persistent pathology related to previous patterns of criminal offending. Conversely, behaviours occurring within institutions that are not topographically similar but that fall within the same response class and do represent the continuation of problematic patterns of behaviour may be ignored if observers are not sensitive to the possibility that problem behaviours, albeit muted, may persist within institutions.

Methods. This paper presents a study examining the similarity of personality disordered patients' violent index acts with their aggressive behaviour during hospitalization.

Results. Results revealed evidence of cross situational similarity for some but not all aggressive behaviours.

Conclusion. These results provide support for the OPB framework. However, the lack of similarity on a significant number of incidents indicates a need for thorough, structured analysis to determine whether an aggressive behaviour observed in an institution parallels violent acts preceding incarceration.