Combined Evaluations of Competency to Stand Trial and Mental State at the Time of the Offense: An Overlooked Methodological Consideration?

Combined evaluations of competency to stand trial (CST; competency) and mental state at the time of the offense (MSO; sanity) frequently co-occur. However, most research examines the 2 as discrete constructs without considering 4 potential combined evaluation outcomes: competent-sane, incompetent-sane, competent-insane, and incompetent-insane. External validity can be improved if research more closely mirrored practice. It may be incorrect to assume incompetent defendants are similar across CST-only and combined evaluations, and insane defendants are similar across MSO-only and combined evaluations. Using a sample of 2,751 combined evaluations, we examined demographic, clinical, offense, evaluation, and psycholegal characteristics associated with evaluators' combined evaluation opinions. Multinomial regression analyses revealed older defendants were more likely to be opined incompetent-insane. Defendants with psychotic disorders were more often opined insane, regardless of competency status. Affective diagnoses predicted competent-insane opinions. Developmental disorders were closely related to incompetence, regardless of sanity status. Defendants with organic disorders tended to have global psycholegal impairment, in that they were more often opined incompetent-insane, incompetent-sane, or competent-insane, relative to competent-sane. Prior hospitalization predicted competent-insane relative to competent-sane opinions. Defendants not under the influence of a substance during the offense or with no prior convictions were more likely to be opined insane, regardless of competency status. We interpret these findings in light of psycholegal theory and provide recommendations for research and practice. Collectively, results suggest incorporation of combined evaluations into CST and MSO research is an important methodological consideration not to be overlooked.