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Mental capacity in England and Wales

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Through Dementia and Learning disability

In a medical emergency, the patient may be obviously incapable of making a decision because they are unconscious and treatment cannot be put off. In that case an attempt to give treatment will be lawful if the person giving the treatment believes it is in the patient's best interest.

Where there is doubt about someone's capacity to make a decision but their capacity may improve later, the decision should be deferred if possible. People who experience delirium or altered states of consciousness, such as during a urinary tract infection, can temporarily lose capacity. If the person's capacity is unlikely to improve in future—such as people who have relatively severe dementia, certain kinds of brain injury, or a serious learning disability—a mental capacity assessment should be conducted. Mental capacity assessments are specific to each decision, so if a different decision is needed, the person's capacity may need to be assessed again. For example, a person might be able to make a decision about their care or treatment but lack capacity to make a financial decision.

Outside an emergency situation, the decision maker should normally take reasonable steps to consult other relevant people (such as the person's next of kin, other relatives, friends or associates) before making a decision on their behalf. If the decision is complex or fraught and will have reasonably serious consequences, an independent advocate should be appointed.

Mental capacity

Key principles

As of 2024, the main legal framework governing mental capacity in adults is set out in the Mental Capacity Act 2005. The key principles are:-

1. A person must be assumed to have capacity unless it is established that he/she lacks capacity.

2. A person is not to be treated as unable to make a decision unless all practicable steps to help him/her to do so have been taken without success.

3. A person is not to be treated as unable to make a decision merely because he/she makes an unwise decision.

4. An act done, or decision made, under this Act for or on behalf of a person who lacks capacity must be done, or made, in his/ her best interests.

5. Before the act is done, or the decision is made, regard must be had to whether the purpose for which it is needed can be as effectively achieved in a way that is less restrictive of the person's rights and freedom of action.

Mental capacity assessments

A diagnosis of (for example) dementia, or a learning difficulty, does not necessarily mean the person lacks capacity. A mental capacity assessment should take place when there is an impairment of, or disturbance in the functioning of a person's mind or brain and a decision that needs to be made. The mental capacity assessment checks whether a person can:-

  • Understand the information they are given;
  • Retain that information for long enough to make a decision;
  • Weigh up the information; and
  • Communicate their decision.

This assessment is made on the balance of probabilities. The person has capacity if they can do all four of these things, and lacks capacity if they cannot do at least one of them. A mental capacity assessment in respect of a lower-level day-to-day decision may be made by a carer or relative and need not be formally recorded, but capacity assessments about decisions that are complex or have important ramifications for the person are made by social workers, doctors or multi-disciplinary teams on behalf of local authorities and clinical commissioning groups, who have a lead role in implementing the Mental Capacity Act and are required to keep formal records.

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