Faulty judgment, expert opinion, and decision-making capacity

An assessment of decision-making capacity is the accepted procedure for det ermining when a person is not competent. An inferential gap exists between the criteria for capacity specific abilities and the legal requirements to understand relevant information and appreciate the consequences of a decisi on. This gap extends to causal influences on a person's capacity to decide. Using a published case of depression, we illustrate that assessors' uses o f diagnostic information is frequently not up to the task of bridging this inferential gap in a justifiable way. We then describe cases of faulty judg ement which challenge the understanding of diagnostic causal influences. Th ese cases help to clarify the nature of the expertise required for capacity assessments. In practice, the requirements of decision-making capacity are often abandoned to other considerations due to a lack of requisite experti se. The legal policy supporting decision-making capacity as a means to prot ective intervention is justified only if the requisite expertise is develop ed. We propose the requisite expertise to be developed in the long term as a distinct multidisciplinary endeavour.