The cusp of capacity: empowering and protecting people in decisions about treatment and care

The law’s cliff-edge approach to mental capacity denies those who lack capacity any right to determine what will happen to them. Consequently, the test for capacity (contained in section 3 of the Mental Capacity Act 2005) must accurately distinguish between those who can and cannot make autonomous decisions. However, the test relies on too narrow a conception of autonomy, preventing it from capturing impairments in the content of the person’s beliefs or values, rather than their decision-making processes. Moreover, whether a decision is autonomous is rarely as clear-cut as the threshold approach presupposes, and there is substantial ambiguity on the cusp of capacity, exacerbated by the realities of assessing capacity in practice. Faced with this uncertainty, decision-makers have sought to manipulate the test through straining the ‘use or weigh’ criterion in section 3, and more readily rebutting the presumption of capacity where the person wishes to do something that will harm them. This thesis therefore advocates introducing a new authenticity limb to the test that asks whether the person’s values or beliefs are the product of an illness or disorder, as well as greater guidance to enhance the consistency with which the test is applied. Even so, as no test can infallibly distinguish autonomous from non-autonomous decisions, the law’s cliff-edge approach needs softening. To address concerns that the best interests provisions currently facilitate risk aversion and paternalism, a new framework is proposed to encourage decision-makers to prioritise the wishes of the individual, through a rebuttable presumption that their wishes be determinative of their best interests unless giving effect to them would expose the person to a serious risk of significant harm. If this is rebutted, the weight accorded to the person’s wishes ought to be proportionate to the strength of those wishes when determining what is in their best interests.