The Roesch-Golding model rejects competency standards based primarily on traditional psychiatric assessment and instead views competency from a functional perspective in which a defendant's cognitive, behavioral, and affective capacities are evaluated relative to the legal demands of the case. The need for greater interaction between legal and mental health professionals in determining competency is emphasized. Prior case law, legal scholarship, and behavioral science research are reviewed. In addition, reforms are proposed in such areas as motions for competency hearings, the use of community-based evaluations, and methods for obtaining more valid and relevant testimony during competency hearings. New approaches to the treatment, reevaluation, and disposition of incompetent defendants are also presented. A major aspect of the model is a collaborative joint screening and evaluation panel composed of legal and mental health professionals. A more controversial part of the model proposes the use of a provisional trial for defendants whose competency remains questionable. Such a procedure offers an opportunity for direct evaluation of competency in an actual situation and allows the validity of current decision schemes for competency to be scrutinized. Moreover, this model can minimize infringement of defendant's rights, help eliminate the present abuses in requests for competency evaluations, and maximize the quality of competency decision. Tables, figures, chapter notes, legal citations, approximately 250 references, and appendixes of related legal information are provided. (Author abstract modified)