The Mental Capacity Act (MCA) of 2005


The Mental Capacity Act (MCA) of 2005 sets out the legal framework for making decisions on behalf of those who have been deemed to lack the mental capacity to make key decisions in their lives.

Who is it for?

  • People over the age of 16 who lack capacity to make specific decisions in their life
  • Health and social care professionals
  • Families and carers of those lacking capacity

Around two million people in England and Wales are thought to lack capacity to make decisions for themselves. They are cared for by a range of health and social care professionals, such as doctors, dentists, social workers, care workers and psychologists. They are also cared for by unpaid carers and family members. All of these people may need to know about the Mental Capacity Act and how it works.


What is “mental capacity?”

Mental capacity is the ability to understand, weigh up, retain and communicate decisions we would like to make. Someone may lack capacity due to impairment of, or disturbance in the functioning of a person’s mind or brain.

The MCA says that a person is unable to make their own decision if they cannot do one or more of the following four things:

  • Understand information given to them
  • Retain that information long enough to be able to make the decision
  • Weigh up the information available to make the decision
  • Communicate their decision – this could be by talking, using sign language or even simple muscle movements such as blinking an eye or squeezing a hand.

A lack of mental capacity could be due to:

  • a stroke or brain injury
  • a mental health problem
  • dementia
  • a learning disability
  • confusion, drowsiness or unconsciousness because of an illness of the treatment for it
  • substance misuse

Capacity is date, time and issue specific, which means that a person may lack the capacity to choose to undergo serious medical treatment, but may have the capacity in other areas of there life, such as choosing where they would like to live. They may also lack the capacity to make a certain decision at one time, but may be able to at a different time.

Who can assess capacity?

Any qualified professional can test capacity, such as a doctor, psychologist or social worker. Capacity should be the person most directly involved with the issue. For health decisions, this should be the doctor. If a lawyer is drawing up a will, but has doubts  about their client’s capacity, they may ask for an expert opinion from a psychiatrist or a psychologist.

The assessment must be made on the balance of probabilities – is it more likely than not that the person lacks capacity? A professional must be able to show in their records why they came to the conclusion that capacity is lacking for the particular decision.

Can capacity change?

Yes. Capacity can change with time because your state of mind can change with time. An illness that interferes with your thinking can get better – at least for a while.  An older person can become confused with a chest infection, so that they can’t make many decisions properly. Their normal state of mind can return when the infection is treated and they can, again, make decisions in the way they normally would.

Disagreeing with a capacity assessment

You can challenge a capacity assessment. Raise this with the person making the assessment at the earliest opportunity, with your reasons for believing that the assessment is not accurate. This should be followed up with putting the reasons in writing and keeping a copy for yourself. Ultimately an individuals’ capacity to make a particular decision can be decided by the Court of Protection.

Five key principles of the MCA

The MCA is underpinned by five key principles.

Principle 1: A presumption of capacity

Every adult has the right to make his or her own decisions and must be assumed to have capacity to do so unless it is proved otherwise. This means that you cannot assume that someone cannot make a decision for themselves just because they have a particular medical condition or disability.

Principle 2: Individuals being supported to make their own decisions

A person must be given all practicable help before anyone treats them as not being able to make their own decisions. This means you should make every effort to encourage and support people to make the decision for themselves. If lack of capacity is established, it is still important that you involve the person as far as possible in making decisions.

Principle 3: Unwise decisions

People have the right to make decisions that others might regard as unwise or eccentric. You cannot treat someone as lacking capacity for this reason. Everyone has their own values, beliefs and preferences which may not be the same as those of other people.

Principle 4: Best interests

Anything done for or on behalf of a person who lacks mental capacity must be done in their best interests.

Principle 5: Less restrictive option

Someone making a decision or acting on behalf of a person who lacks capacity must consider whether it is possible to decide or act in a way that would interfere less with the person’s rights and freedoms of action, or whether there is a need to decide or act at all. Any intervention should be weighed up in the particular circumstances of the case.


Best interests decision-making

If a person has been assessed as lacking capacity then any action taken, or any decision made for or on behalf of that person, must be made in his or her best interests (principle 4). The person who has to make the decision is known as the ‘decision-maker’ and normally will be the carer or care worker responsible for the day-to-day care, or a professional such as a doctor, nurse or social worker where decisions about treatment, care arrangements or accommodation need to be made.

However Best Interests decisions can only be made on decisions which the person would usually be able to make themselves, such as moving home. Other issues such as a reduction in the amount of care a person receives from the local authority would not qualify for a Best Interests process.

What is ‘best interests’, and how is it decided?

The MCA provides a non-exhaustive checklist of factors that decision-makers must work through in deciding what is in a person’s best interests. This checklists includes:

  • Any known past wishes or feelings from the person about the issue
  • A person can put his/her wishes and feelings into a written statement if they so wish, which the person determining capacity must consider.
  • People involved in caring for the person lacking capacity have to be consulted concerning a person’s best interests.

Deciding what is in the best interests of a person usually requires the decision maker along with those involved with the person’s life, and the person themselves (to the best of their ability) to weigh up the benefits and burdens of each available option.


Disagreeing with a Best Interests decision

There may be situations where you wish to challenge a decision, for example if you think you have not been consulted properly, or a decision is made which you do not think is in the best interests of your friend or relative. You may be involved in situations where there is disagreement, perhaps among family members or between family and a professional, about a decision such as what is in a person’s best interests. There are a number of steps you can take in these situations.

  • Involving an independent advocate (not an IMCA) who can help make sure your friend or relative’s wishes and feelings are properly understood may help to resolve disputes.
  • Making a formal complaint. The NHS, local authorities, voluntary and private care homes all have formal complaints processes. If your complaint is about the NHS then you can find more help from us here, or contact the local PALS (Patient Advice and Liaison Service) team.
  • The Office of the Public Guardian (OPG) will be able to give advice and information about disputes under the Mental Capacity Act.
  • The Court of Protection (CoP) can make a ruling if other methods are not suitable. You might want to get help from a solicitor or Citizens Advice Bureau about this.

Independent Mental Capacity Advocate (IMCA)

The MCA created the role of a qualified independent person to support the person who is lacking capacity. The IMCA role is available to those who:

  • lack the capacity to make a key decision about their life
  • are unbefriended (i.e they have no family or unpaid carers to support them)

The role of the IMCA is to support the person lacking capacity to make their wishes and preferences known to the best of their ability, and to contribute to, and represent the person in Best Interest processes. They also have the authority to challenge capacity assessments, best interests decisions, and to request applications to the Court of Protection (CoP).

This differs from other most types of advocacy, as usually an advocate cannot voice their own views or what they believe is in a person’s best interests. Most other types of advocate can also not make challenges on behalf of someone else.