A Short Guide to the Mental Capacity Act 2005

This article, which I co-wrote with Abigail Taylor, a 5th year medical student at Oxford, is intended for healthcare professionals.

It guides the reader through the Mental Capacity Act 2005 (MCA) with the aim of clearing up several areas of lasting confusion, particularly in relation to the MCA Deprivation of Liberty Safeguards (DoLS) and its apparent overlap with the Mental Health Act.

The Mental Capacity Act

The Mental Capacity Act 2005 is a piece of legislation intended to protect people who lack the ability to make decisions about their health, welfare, and finances. It replaces Part 7 of the Mental Health Act 1983 and the Enduring Powers of Attorney Act 1985, and was introduced to clarify legal uncertainties around decision-making on behalf of adults with mental incapacity, and to create new safeguards.

Main Principles

  1. Presumption of capacity: a person is presumed to have capacity to make a decision unless it is established otherwise.
  2. Maximising capacity: before a person is deemed to lack capacity, all practicable steps must have been taken to help that person make his own decisions.
  3. Right to make unwise decisions: a person must not be treated as unable to make a decision merely because the decision appears unwise to others.
  4. Best interests: decisions made on behalf of a person who lacks capacity must be made in their best interests.
  5. Least restrictive option: those courses of action that are less restrictive to the person’s rights and freedom must be considered first.

Definition of capacity

Section 2 of the MCA defines capacity as follows:

‘a person lacks capacity in relation to a matter if at the material time he is unable to make a decision for himself in relation to the matter because of an impairment of, or a disturbance in the functioning of, the mind or brain.’

Capacity v. competence

  • Competence is the legal right to have one’s decision regarding treatment respected. It is a binary concept: a person is either ‘competent’ or not.
  • Capacity refers to the natural ability to make decisions: a person has a certain degree of capacity in relation to a particular decision at a particular time.
  • Competence is informed by capacity: if capacity is beyond a certain threshold, the person is deemed ‘competent’ to make a decision. This threshold varies according to the seriousness of the decision at hand.

Capacity is contextual and should not simply be inferred from the patient’s diagnosis or from previous assessments of his capacity.

According to Section 3 of the MCA, a person has capacity to make a particular decision if he:

  • Understands the information relevant to decision-making.
  • Retains the information for long enough to make a decision.
  • Weighs-up the information and understands the consequences of a decision.
  • Communicates this decision by whatever means necessary.

Assessment of capacity in adults

Stage 1: Diagnostic test

Assess whether there is a disturbance or impairment of the mind (e.g. intoxication, head injury, learning disabilities, or dementia) which may affect decision-making at this point in time. Your assessment must lean on standardised criteria such as the ICD-10 or DSM-V diagnostic criteria.

Stage 2: Functional test

Assess by the four criteria in Section 3 of the MCA whether this disturbance or impairment renders the person unable to make a decision about the matter in hand. Your assessment should be made on the ‘balance of the probabilities’, meaning that it is more likely than not that the person lacks capacity to make that decision.

Efforts to optimise capacity might include:

  • Making your explanations easier to understand e.g. by using diagrams.
  • Seeing the patient at his best time of day.
  • Seeing him with one of his friends or relatives.
  • Improving his environment e.g. finding a quiet side-room.
  • Adjusting his medication e.g. decreasing the dose of sedative drugs.

Remember to document your assessment and to outline your reasoning.

Assessment of capacity in children and adolescents

As far as possible, minors ought to be involved in decisions about their care, whether or not they are deemed competent.

  • Decisions on behalf of a minor can be made by a person with parental responsibility or by a High Court.
  • 16- and 17-year-olds are deemed competent by the same standards as adults (Family Law Reform Act 1969). However, they cannot refuse treatment if it has been agreed by a person with parental responsibility or the Court and it is in their best interests.
  • Under-16s may be deemed competent to accept an intervention if they are mature enough to fully understand what is proposed (‘Gillick competency’, after Gillick v. West Norfolk and Wisbech Area Health Authority, 1986). Much will depend on the relationship between the clinician and the child and the family, and also on what intervention is being proposed.
  • Ideally, the consent of a person with parental responsibility should also be sought. However, the decision of a competent minor to accept treatment cannot be overruled by a parent.
  • A court order may be obtained to overrule the decision of a competent minor or parent if it is considered in the best interests of the minor.

Deprivation of Liberty Safeguards

The Deprivation of Liberty Safeguards (DoLS) is an amendment to the MCA intended to protect vulnerable adults in care from arbitrary or excessive restrictions on their freedom, and also to give them the right to legally challenge their detention.

In practice, DoLS is pertinent to most mentally incapacitated adults living in care who, for the sake of their own welfare, are prevented from leaving. In such cases, the hospital or care home must apply for authorisation from a DoLS supervisory authority, whether or not the patient (who lacks capacity) is ‘agreeing’ to the arrangements.

DoLS is not applicable to people detained under the Mental Health Act (MHA).


The MHA applies to people with a mental disorder who need to be detained for assessment or treatment in the interests of their own health and safety or the safety of others (see Station X). DoLS is used for people with mental disorders such as dementia and learning disabilities who do not require assessment and for whom there is no medical treatment (for the mental disturbance), and who therefore do not meet the MHA criteria, but who nevertheless require deprivation of liberty for their wellbeing, including for the treatment of physical illness.


Advance decisions

Formerly known as advance directives or living wills, advance decisions enable a person to make decisions about their future care in the event that they come to lack the capacity to make these decisions. An advance decision can only be used to refuse, not to demand. It is valid if it is unambiguous, applicable to the circumstances, and written without coercion at a time when the person had an appropriate level of capacity. If related to life-sustaining treatments, it must also be dated and signed by an adult witness.

Lasting Power of Attorney (LPA)

An LPA is a legal document stating that one person has chosen another to make decisions about his welfare on his behalf, should he lose capacity. There are two types of LPA, personal welfare and property and affairs.

Court of Protection

The Court of Protection can rule upon whether a person has capacity, and, if not, appoint deputies (usually relatives or friends) to make decisions on his behalf. It usually has the final say in the event of a dispute about the best interests of the person who lacks capacity.

The full text of the MCA is available at http://www.legislation.gov.uk/ukpga/2005/9/section/1