Understanding mental capacity and the five principles

The Mental Capacity Act 2005 applies in England and Wales to people aged 16 and over. It protects people who may be unable to make some decisions for themselves and establishes that adults should be assumed able to decide unless there is evidence otherwise.

Mental capacity is decision-specific and time-specific. Someone may be able to make one decision but not another, or be able to decide at one time of day and not at another. The Act therefore requires assessment in relation to the particular decision that needs to be made.

The five principles

• Start with the presumption of capacity: assume the person can decide unless there is evidence to the contrary.
• Support the person to decide: take all practical steps to help them before concluding they lack capacity.
• Do not confuse an unwise decision with incapacity: people are permitted to make decisions others disagree with.
• Act in best interests if capacity is lacking: any decision made for someone else must focus on their needs and circumstances.
• Choose the least restrictive option: restrict the person's rights or freedom as little as possible while addressing the need.

Scope and limits

This course focuses on England and Wales. Scotland and Northern Ireland use different legislation and processes: Scotland has the Adults with Incapacity (Scotland) Act 2000 and commonly uses a section 47 certificate of incapacity for treatment; Northern Ireland has the Mental Capacity Act 2016 and its own arrangements. The MCA does not apply to children under 16, who are governed by separate rules on consent and competence.

A diagnosis does not prove incapacity. The law concerns whether the person can make the specific decision that now needs to be made.