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Factsheet: What is Mental Capacity?

Mental capacity is the ability to make decisions for yourself. People who cannot do this are said to ‘lack capacity’. This might be due to illness, injury, a learning disability, or mental health problems that affect the way their brain works.

To have capacity a person must be able to:

  • Understand the information that is relevant to the decision they want to make
  • Retain the information long enough to be able to make the decision
  • Weigh up the information available to make the decision
  • Communicate their decision by any possible means, including talking, using sign language, or through simple muscle movements such as blinking an eye or squeezing a hand

People should be assumed to have capacity unless there is clear evidence that shows otherwise. Where capacity is in question, the person should be assessed by a suitably qualified professional on whether they have the ability to make a particular decision at a particular time. The mental capacity of a person can fluctuate. As an example, for a person with dementia there might be times of the day when they are able to think more clearly. Where a person has fluctuating capacity they should, where possible, be assisted to make the decision at the time that they have capacity to do so.

  1. Lack of Mental Capacity
  2. What law governs Mental Capacity?
  3. What is the Mental Capacity Act (MCA) used for?
  4. What happens when someone does not have capacity?
  5. What is Best Interests?
  6. Code of Practice for the Mental Capacity Act 2005
  7. The five key principles of the MCA
  8. What is the Court of Protection?

Understanding the Mental Capacity Act 2005 and how it affects you.

Lack of Mental Capacity

A lack of capacity could be because of:

  • A learning disability
  • Mental health problems
  • Brain injury
  • Dementia
  • Alcohol or drug use
  • Side effects of medical treatment or a serious illness or disability
  • Any other mental impairment or disability

The Act sets out a test for assessing whether a person has the capacity to make a particular decision at a particular time. It is a ‘decision-specific’ test, concerned only with the decision that has to be made. For example, someone may be quite capable of making decisions about some matters like their weekly food shop, but unable to deal with large sums of money or consent to a necessary operation.

The test is in two stages:

  1. It must be determined whether the person has an impairment of the mind or the brain, or some other disturbance that affects the way their brain works, and;
  2. If so, whether the disturbance is so great that they lack the ability to make the particular decision

In deciding the second part of the test, a person will lack the capacity to make a particular decision if they cannot:

  • Understand information relevant to the decision
  • Retain that information
  • Use or weigh that information when making the decision; or
  • Communicate a decision in any way

If a person cannot do any one of the above things, they will lack the capacity to make the decision. No one can be labelled ‘incapable’ on the basis of a particular diagnosis, and the second part of the capacity test must always be considered.

What law governs Mental Capacity?

The Mental Capacity Act 2005 (MCA) provides a framework to protect vulnerable people over the age of 16 who are not able to make their own decisions. If someone cannot make a certain decision for themselves, they are said to ‘lack capacity’ to make the decision.

The Act makes it clear who can take decisions in which situations, and how they should go about this. It also enables people to plan ahead for a time when they may lose capacity.

The Mental Capacity Act 2005 gives a legal definition of ‘mental capacity‘. Where a person does not have capacity to make decisions, the law provides safeguards and protection, including giving limited powers to third parties to take decisions on their behalf. In cases where there is a real dispute about whether something is in the best interests of a person without capacity then an application can be made to the Court of Protection for it to decide the issue.

The Mental Health Act 1983 (not to be confused with the Mental Capacity Act) is the legislation that should normally be used when a person with a mental illness refuses treatment for their mental health and this affects their health or puts them or others at risk. However, the Mental Capacity Act might be used to make a ‘one-off’ decision about treatment or in order to compel a person with a mental illness to accept treatment for a physical condition.

The Mental Capacity Act also makes it clear that a lack of capacity cannot be established merely by reference to a person’s age, appearance, or any condition or aspect of a person’s behaviour which might lead others to make unjustified assumptions about capacity.

What is the Mental Capacity Act (MCA) used for?

The Mental Capacity Act allows other people to make decisions for people who lack the capacity to make these decisions for themselves. The Act does this by creating the roles of ‘Attorney’ appointed under a ‘Lasting Power of Attorney‘ (LPA) and ‘Deputy’. It also provides safeguards to ensure the decisions made on behalf of a person are made in their best interests.

Where a decision has to be made for a person that lacks capacity and it is made properly and following the requirements of the MCA, the person making the decision is protected from legal action.

What happens when someone does not have capacity?

If a health or social care professional has to make a decision for somebody else they will use the MCA Code of Practice to make an assessment of that person’s capacity to make that particular decision. An assessment must be done to ensure that the person definitely does not have capacity, before any decisions are made. The professional will talk to the person and should involve anyone else who is appropriate such as carers, family and doctors to make a decision in the person’s best interests. A formal Best Interest Meeting may be needed to make decisions for more complex issues and significant changes, such as decisions about long-term care or moving into a care home. A formal meeting can ensure that the person has the chance to have their opinions heard and recorded, and can include other relevant people as appropriate.

Unfortunately, the correct procedure for making ‘Best Interest’ decisions is not always followed. You should seek specialist advice from our Community Care Law Team if you have any concerns.

What is Best Interests?

The Act confirms that everything that is done for, or on behalf of, a person who lacks capacity must be in that person’s best interests. The Act provides a checklist of factors that decision makers must work through in deciding what is in a person’s best interests. The person’s wishes and feelings should be central in the decision-making process and the person should be consulted where possible. Also, carers and family members have a right to be consulted.

Code of Practice for the Mental Capacity Act 2005

The Mental Capacity Act covers important decisions relating to an individual’s property, financial affairs, and health and social care. It also applies to everyday decisions, such as personal care, what to wear and what to eat.

The Mental Capacity Act is accompanied by a Code of Practice which provides more in-depth guidance for professional staff such as social workers.

The code of practice for the Mental Capacity Act gives guidance on how the Act should work on a day-to-day basis. It provides case studies and explains in detail the key features of the law.

The five key principles of the MCA

The MCA is based on five key principles that must be followed by anyone who is considering making a decision for someone else:

  1. Someone is presumed to have capacity unless it is proved otherwise
  2. Individuals must be supported to make their own decisions, for example with the help of counselling or medication, and be given all appropriate information before it is decided they do not have capacity
  3. People have a right to make decisions others may see as eccentric or unwise, provided they have the capacity to make the decision
  4. Anything done for someone without capacity must be in their best interests
  5. Anything done for someone without capacity must be the least restrictive of their basic rights and freedoms

What is the Court of Protection?

Deputies are appointed to make decisions for people who lack the capacity to do so themselves. This applies in situations where formal arrangements have not been made – for example, if a person loses capacity and has not set up a Lasting Power of Attorney or an advance decision. A Deputy is usually a friend or relative of the person who lacks capacity, but could also be a professional. To become a Deputy you must apply to the Court of Protection. Deputies must make decisions in the best interests of the person lacking capacity. These might be about property or financial affairs, such as redeeming an insurance policy or selling a house.

The Court of Protection also has authority to make official decisions (called orders) about any healthcare, welfare or financial matters.

Where there is a dispute that cannot be resolved between the professionals, the person and/or their relatives about what is in the person’s best interests, the matter should be referred to the Court of Protection for the decision to be made.

Speak to our expert mental capacity and Court of Protection lawyers to find out how we can help you. Contact us on 01273 609911, or email

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