Competency and common law: why and how decision-making capacity criteria should be drawn from the capacity-determination process.

Determining competence to request physician-assisted suicide should be no more difficult than determining competence to refuse life-prolonging treatment. In both cases, criteria and procedures should be developed out of the process of actually making capacity determinations; they should not be promulgated a priori. Because patient demeanor plays a critical role in capacity determinations, it should be made part of the record of such determinations through greater use of video- and audiotapes.