Mental capacity in England and Wales

In the law of England and Wales, best interest decisions are decisions made on behalf of people who do not have mental capacity to make them for themselves at the time the decision needs to be taken.^[1] Someone who has the capacity to make a decision is said to be "capacitous". Since 2007, there has been a dedicated court with jurisdiction over mental capacity: the Court of Protection, although it mostly deals with adults. Most applications to make decisions on behalf of a child are still dealt with by the Family Court.

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.