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Logo of bmjThis ArticleThe BMJ
BMJ. 2007 November 3; 335(7626): 898.
PMCID: PMC2048843

Mental Capacity Act 2005

Andrew Alonzi, senior lecturer in law1 and Mike Pringle, professor of general practice2

Should guide doctors to help protect vulnerable people

The Mental Capacity Act 2005, which was fully implemented on 1 October 2007, is intended to protect people who lack capacity to make decisions and to encourage them to participate in the decisions that are intended to help them. It presents, however, a new range of challenges for doctors, but it should help clarify actions in difficult situations.

A helpful code of practice that supports the act guides people treating or caring for adults who lack the capacity to make decisions about their treatment or care,1 and it is all most doctors will need. This code has statutory force, which means that practitioners now have a legal duty to take note of the code when working with or caring for adults who lack capacity to make decisions for themselves. However, there is no legal duty to comply with the code, although evidence of non-compliance may be used by a court or tribunal—for example, in a claim for damages for clinical negligence.

Several principles underpin the act. A person must be assumed to have capacity to make decisions unless evidence to the contrary is available. All practical steps must be taken to help someone make a decision before incapacity is assumed. Just because someone makes an unwise decision does not mean that they are incapacitated. If you make a decision on someone's behalf, it must be in their best interests, and there must be no better way of achieving the same outcome.

Who lacks mental capacity? The answer is any person who is unable to make a particular decision or take a particular action at the time the decision or action needs to be taken. A doctor has to judge whether the functioning of the mind or brain is sufficiently impaired or disturbed, permanently or temporarily, that the person lacks the capacity to make a particular decision.

How does a doctor act in the patient's best interest? To determine what is in a person's best interests, the doctor should encourage the person to participate in the decision making process; try to identify the views and factors that would have influenced them if they had capacity to make the decision (such as evidence of past and present wishes and feelings; religious, cultural, or moral beliefs and values); avoid assumptions about best interests based on age, appearance, condition, or behaviour; consider whether they are likely to regain capacity after medical treatment (which implies that the decision could be delayed until then); and not be motivated by a desire to bring about death or be influenced by assumptions about quality of life, if the decision is about life sustaining medical treatment.

The doctor should consult with others—while being careful not to breach confidentiality—for their views when trying to determine what is in the person's best interests, and to see if they have any information about the person's wishes, feelings, beliefs, and values. Whatever is decided must also be the least restrictive option available to the person, in terms of their rights and freedoms. The doctor must record how the decision on best interests was reached (for example, the reasons, who was consulted, and what special factors were considered).

Can a doctor be liable for his or her decision? If certain conditions are met, doctors are protected from civil or criminal liability when performing tasks in the best interests of a person who lacks capacity. In emergency situations, for example, it will almost always be in the person's best interests to give urgent treatment without delay, unless a valid and applicable advance decision to refuse medical treatment is in place.

This protection does not, however, provide defence against a claim of negligence. For example, if a person who lacks capacity is restrained, the act does not protect against liability unless it can reasonably be believed that restraint is needed to prevent harm to the person. The amount and type of restraint used and the time that it lasts must also be proportionate to the likelihood and seriousness of harm.

The act also covers advance decisions to refuse medical treatment. If a valid, applicable advance decision to refuse treatment exists a doctor must respect it. A doctor following an advance decision will be protected from liability. If the doctor knows such a decision exists and does not follow it, the doctor will not be covered. Even if an advance decision is not valid or applicable to the circumstances, it still should be considered by healthcare staff as an expression of previous wishes when working out the person's best interests.

Whenever treating a person who might have impaired capacity, the code needs to form a conscious part of a doctor's decision making process. Clear evidence of alignment with the code's guidance must exist, particularly if decisions or treatments are called into question. This will require education for staff at all levels. Health professionals should be encouraged to reflect on their practice in the context of the code's guidance and to discuss experiences openly and frankly.


Competing interests: None declared.

Provenance and peer review: Commissioned; not externally peer reviewed.


1. Department of Constitutional Affairs. Mental Capacity Act 2005 Code of practice.

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