Mental Capacity Act 2005

28. It is a key principle of the Act that all steps and decisions taken for someone who lacks capacity must be taken in the person’s best interests. The best interests principle is an essential aspect of the Act and builds on the common law while offering further guidance. Given the wide range of acts, decisions and circumstances that the Act will cover, the notion of “best interests” is not defined in the Act. Rather, subsection (2) makes clear that determining what is in a person’s best interests requires a consideration of all relevant circumstances (defined in subsection (11)). Subsection (1) makes clear that best interests determinations must not be based merely on a person’s age, appearance, or unjustified assumptions about what might be in a person’s best interests based on the person’s condition or behaviour. Best interests determinations must not therefore be made on the basis of any unjustified and prejudicial assumptions. For example, in making a best interests determination for a person who has a physical disability it would not be acceptable to assume that, because of this disability, they will not have a good quality of life and should therefore not receive treatment. As with section 2(3) the references to “condition” and “appearance” capture a range of factors. The section goes on to list particular steps that must be taken. Best interests is not a test of “substituted judgement” (what the person would have wanted), but rather it requires a determination to be made by applying an objective test as to what would be in the person’s best interests. All the relevant circumstances, including the factors mentioned in the section must be considered, but none carries any more weight or priority than another. They must all be balanced in order to determine what would be in the best interests of the person concerned. The factors in this section do not provide a definition of best interests and are not exhaustive.