Constructing and reconstructing 'best interests': An interpretative examination of substitute decision-making under the Mental Capacity Act 2005.

The Mental Capacity Act 2005 (MCA) authorises substitute decision-making in England and Wales, in relation to 'acts in connection with care or treatment', for a person lacking the capacity to make an autonomous decision, if it is both necessary and in his or her 'best interests'. The approach adopted by the MCA is consistent with the common law, but widens both the scope and procedures of a 'best interests' determination to allow for a general model of substitute decision-making in everyday health and social care. However, by decontextualising substitute decision-making, the MCA's procedures relating to 'best interests' may prove to be problematic in three ways: first, by failing to resolve adequately certain ethical dilemmas that pervade this area; secondly, by reducing applied substitute decision-making to a series of compulsory generalised instructions; and, finally, by necessitating deliberation but offering little practical guidance to the process of determination. Whilst the codification of five statutory principles in the MCA is designed to foster the empowerment of vulnerable adults, the realisation of these procedural and conceptual problems may have a negative impact on the implementation of the Act.