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.
Charles H. Baron. "Competency and Common Law: Why and How Decision-Making Capacity Criteria Should Be Drawn from the Capacity-Determination Process." Psychology, Public Policy and Law 6, (2000): 373-381.