Mental Capacity Act Basics

The Mental Capacity Act is built on five core principles that must guide all decisions made under it:

1. Presumption of capacity — Every adult must be assumed to have capacity to make a decision unless it is established that they lack capacity. Capacity must never be assumed to be absent because of age, disability, or diagnosis.
2. Right to be supported to make decisions — All practicable steps must be taken to help a person make their own decision before concluding they lack capacity. This might mean using simpler language, visual aids, or waiting until a better time of day.
3. Right to make unwise decisions — A person is not to be treated as lacking capacity merely because they make an unwise or eccentric decision. Adults have the right to make choices others disagree with.
4. Best interests — Any act done or decision made for someone who lacks capacity must be done in their best interests (see the Best Interests guide).
5. Least restrictive option — Before doing something or making a decision, regard must be had to whether there is a less restrictive way of achieving the desired purpose.

Under the MCA, a person lacks capacity in relation to a specific decision if at the relevant time they are unable to make the decision because of an impairment of, or a disturbance in, the functioning of the mind or brain. The capacity test has two stages:

Stage 1 (diagnostic) : Is there an impairment of, or disturbance in, the functioning of the mind or brain? This could be dementia, brain injury, mental illness, learning disability, substance intoxication, or any other cause.

Stage 2 (functional): As a result, is the person unable to: understand the information relevant to the decision; retain that information; use or weigh it as part of the decision-making process; or communicate their decision (by any means)?

Both stages must be satisfied for a finding of incapacity. Incapacity is decision-specific — a person may lack capacity for complex financial decisions but retain capacity for decisions about daily care, food preferences, or social activities.

The Deprivation of Liberty Safeguards (DoLS) are a set of checks under the MCA that protect people in care homes and hospitals who lack capacity and whose care arrangements amount to a deprivation of their liberty. Following the Supreme Court's landmark judgment in Cheshire West (2014), the threshold for deprivation of liberty is low — many arrangements that had not previously been considered restrictive were found to cross the threshold.

DoLS require care homes and hospitals to apply to the supervisory body (the local council for care homes; NHS England for hospitals) for authorisation of the deprivation of liberty. The authorisation process includes independent assessments of mental health, mental capacity, and best interests. Unauthorised deprivations of liberty are unlawful.

DoLS is being replaced by the Liberty Protection Safeguards (LPS), a reformed system under the Mental Capacity (Amendment) Act 2019. As of April 2025, LPS implementation is ongoing — check current status, as the transition affects how assessments are conducted.