Ethics England Wales

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2. General information

The Mental Capacity Act 2005

The Mental Capacity Act 2005 provides a comprehensive framework for decision making on behalf of adults aged 16 and over who lack capacity to make decisions on their own behalf. The Act applies to England and Wales. Scotland has its own legislation, the Adults with Incapacity (Scotland) Act 2000. The approach in Northern Ireland is currently governed by the common law, although at the time of writing, change was anticipated.

The Act applies to all decisions taken on behalf of people who permanently or temporarily lack capacity to make such decisions themselves, including decisions relating to medical treatment. All doctors working with adults who lack, or who may lack, capacity will need to be familiar with both its underlying principles and its basic provisions. This tool kit sets out the main features of the Act in so far as it relates to decisions about medical treatment.

The Act is accompanied by a statutory Code of Practice providing guidance on how it should be used. Certain people have a legal duty to have regard to the guidance in the Code of Practice, including anyone acting in a professional capacity or being paid for their work with people who may lack capacity. It is therefore essential that health professionals are familiar with the Code of Practice.


What is capacity?

Decision making capacity refers to the everyday ability that individuals possess to make decisions or to take actions that influence their life, from simple decisions about what to have for breakfast, to far reaching decisions about serious medical treatment.

In a legal context it refers to a person’s ability to do something, including making a decision, which may have legal consequences for the person themselves or for other people.


When does a person lack capacity?

For the purpose of the Act a person lacks capacity if, at the time the decision needs to be made, he or she is unable to make or communicate the decision because of an ‘impairment of, or a disturbance in the functioning of, the mind or brain’.

The Act contains a two-stage test of capacity:

  • is there an impairment of, or disturbance in the functioning of, the person’s mind or brain? If so:
  • is the impairment or disturbance sufficient that the person is unable to make that particular decision?

In practice it can be helpful to ask three questions:

  1. Does the person have an impairment of, or a disturbance in the functioning of, their mind or brain?
  2. Is the person unable to make a specific decision at the time it needs to be made for one or more of the reasons given in the Act? (See card 5)
  3. Is the person’s inability to make the specific decision at the time it needs to be made because of the aforementioned impairment or disturbance in the person’s mind or brain?

The assessment of capacity is ‘task specific’. It focuses on the specific decision that needs to be made at the specific time the decision is required. It does not matter if the incapacity is temporary, or the person retains the capacity to make other decisions, or if the person’s capacity fluctuates. The inability to make a decision, however, must be a result of the impairment or disturbance already mentioned.

This could be the result of a variety of factors, including mental illness, learning disability, dementia, brain damage, or intoxication. The important point is that the impairment or disturbance renders the individual unable to make the decision in question.

If the impairment is temporary and the decision can realistically be put off until such time as he or she is likely to regain capacity, then it should be deferred. While it is clear that an unconscious patient will lack capacity, most other categories of patient will retain some decision-making capacity, however slight.


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Card 2 (PDF)