“Competence” of criminal defendants is best viewed not as an open-textured single construct but rather as two related but separable constructs-a foundational concept of competence to assist counsel, and a contextualized concept of decisional competence. This approach has several advantages. First, it provides a useful explanatory framework for the settled features of existing law. Second, it helps to clarify the issues in areas where the law is unsettled or controversial, such as the circumstances under which incompetence bars adjudication and the abilities required for decisional competence. Third, it exposes the similarities between competencies in criminal defense and competencies in other legal contexts, and thereby helps to link what have been discrete literatures in both law and behavioral science. Fourth, because this approach is derived from a theoretical analysis of the purposes of the pertinent legal rules, it provides a framework for defining the “psycho-legal abilities” that are encompassed by each of the two competence constructs. In this respect, a relatively simple reconceptualization has surprisingly concrete implications for designing a program of empirical research and, eventually, for improving the scientific basis of competence assessments in criminal cases.

Richard J. Bonnie, The Competence of Criminal Defendants: A Theoretical Reformulation, 10 Behavioral Sciences & the Law 291–316 (1992).