THE MACARTHUR ADJUDICATIVE COMPETENCE STUDY - DEVELOPMENT AND VALIDATION OF A RESEARCH INSTRUMENT

Assessment of competence to stand trial is a common evaluation that ca n have substantial consequences for defendants and the criminal justic e system. Despite a voluminous literature, much remains unknown. An ob stacle to progress in understanding what is better termed ''adjudicati ve competence'' is the absence of structured standardized research mea sures for assessment of defendants. This article presents the legal fr amework assessment strategy, instrument description, psychometric prop erties, and construct validation of the MacArthur Structured Assessmen t of the Competencies of Criminal Defendants (MacSAC-CD). The measures meet or exceed accepted indices of internal consistency, and intersco rer agreement. Observed patterns of correlations among measures suppor t the underlying theoretical structure of competence-related abilities . Moreover the MacSAC-CD distinguishes groups of competent and incompe tent defendants; reflects changes in competence status; and correlates positively with clinical judgments, negatively with psychopathology a nd impaired cognitive functioning, and negligibly with cynicism toward the justice system.