FREE CHAPTER from ‘A Practical Guide to Assessing Mental Capacity’ by Holly Chantler


The current legal framework in relation to mental capacity was established by the Mental Capacity Act 2005 (“MCA”). The MCA makes it clear that the definition of lack of capacity and the test of capacity as set out in the MCA are “for the purposes of the Act” and as such, will only apply to decisions covered by the MCA. This is affirmed in the MCA Code of Practice at paragraph 4.33, which states that the statutory definition of capacity is in line with common law tests and the MCA does not replace them. There is some academic debate as to the extent this is correct and so in some circumstances, particularly in relation to wills, it may be necessary to apply the MCA and common law concurrently. However, for the purposes of most legal decisions, it is the MCA test of capacity that will apply.

Section 1 Mental Capacity Act 2005: the principles

All decisions made on behalf of or in respect of a person who lacks capacity must be made pursuant to the principles of the MCA, as set out in section 1. These principles are:

  1. A person must be assumed to have capacity unless it is established that he lacks capacity.

  2. A person it not to be treated as unable to make a decision unless all practicable steps to help him to do so have been taken without success.

  3. A person is not to be treated as unable to make a decision merely because he makes an unwise decision.

  4. An act done or decision made under the MCA for or on behalf of a person who lacks capacity must be done, or made, in his best interests.

  5. Before the act is done, or the decision is made, regard must be had as to whether the purpose for which it is needed can be as effectively achieved in a way that is less restrictive of the person’s rights and freedom of action.

Section 1(2) Mental Capacity Act 2005: presumption of capacity

The MCA creates a rebuttable presumption of capacity, reflecting the common law position (as identified by Kennedy LJ in his Court of Appeal judgment in Masterman-Lister v Jewell [2003] 3 All ER 162 where he stated that capacity was a right ‘with which no lawyer and no court should rush to interfere”).

In practice, where concerns are raised regarding a client’s capacity to provide instructions, it may be necessary for a formal assessment of capacity to be carried out, either by the practitioner or by a medical expert. This is covered more below.

The presumption of capacity still applies even where a client has a deputy or attorney appointed and the practitioner will still need to satisfy themselves that the client lacks capacity to take the decision in question. The legal basis for this is that the deputy or attorney only has authority to make a decision on behalf of the client if the client lacks capacity to make the decision for themselves. There is a significant risk to the practitioner if they fail to ascertain the client’s capacity. The practitioner’s duty is to the client; the deputy or attorney is acting as an agent only. This is covered in further detail later in the book.

Section 1(3) Mental Capacity Act 2005: providing practical support

In addition to the presumption of capacity, section 1 MCA further states that “a person it not to be treated as unable to make a decision unless all practicable steps to help him to do so have been taken without success” (section 1(3) MCA). A practitioner cannot assume that a person lacks capacity to take a particular decision on the basis that they are unable to assimilate, process or communicate their decision making. Consideration should be had as to how a person can be supported to make a decision – in some situations this may be relatively easy, for example using braille for someone with a visual impairment (assuming the person feels comfortable communicating in this way), but in other situations this may be more difficult and require creative thinking. Supportive decision making is a key part of section 1(3) MCA and is considered further below.

Section 1(4) Mental Capacity Act 2005: unwise decisions

Section 1(4) MCA states that “a person is not to be treated as unable to make a decision merely because he makes an unwise decision”. The MCA therefore creates a statutory framework designed to preserve a person’s “freedom and autonomy” (see Simpson v Simpson [1989] Fam Law 20).

It is not unusual for individuals to make decisions that others would not; it is a natural part of human behaviour. It is imperative that the decision maker does not seek to substitute their own views or decision making when considering another’s decision. A seemingly unwise decision is not indicative of an incapacitous decision and the individual nature of decision making must be respected.

This principle can be more effectively applied when the decision maker knows more about the individual as a person and whether the proposed decision is in line with the type of decision they would usually make (although as emphasised above, an unusual decision does not mean the person lacks capacity to make the decision in person).

Section 1(5) Mental Capacity Act 2005: best interests

If it has been established that the person to whom the decision relates lacks capacity to take the decision in question, any decision made on behalf of that person must be taken in his or her best interests. Section 4 MCA sets out what constitutes best interests:

4 Best interests

  1. In determining for the purposes of this Act what is in a person’s best interests, the person making the determination must not make it merely on the basis of—

  1. the person’s age or appearance, or

  2. a condition of his, or an aspect of his behaviour, which might lead others to make unjustified assumptions about what might be in his best interests.

  1. The person making the determination must consider all the relevant circumstances and, in particular, take the following steps.

  2. He must consider—

  1. whether it is likely that the person will at some time have capacity in relation to the matter in question, and

  2. if it appears likely that he will, when that is likely to be.

  1. He must, so far as reasonably practicable, permit and encourage the person to participate, or to improve his ability to participate, as fully as possible in any act done for him and any decision affecting him.

  2. Where the determination relates to life-sustaining treatment he must not, in considering whether the treatment is in the best interests of the person concerned, be motivated by a desire to bring about his death.

  3. He must consider, so far as is reasonably ascertainable—

  1. the person’s past and present wishes and feelings (and, in particular, any relevant written statement made by him when he had capacity)

  2. the beliefs and values that would be likely to influence his decision if he had capacity, and

  3. the other factors that he would be likely to consider if he were able to do so.

  1. He must take into account, if it is practicable and appropriate to consult them, the views of—

  1. anyone named by the person as someone to be consulted on the matter in question or on matters of that kind,

  2. anyone engaged in caring for the person or interested in his welfare,

  3. any donee of a lasting power of attorney granted by the person, and

  4. any deputy appointed for the person by the court

as to what would be in the person’s best interests and, in particular, as to the matters mentioned in subsection (6).

  1. The duties imposed by subsections (1) to (7) also apply in relation to the exercise of any powers which—

  1. are exercisable under a lasting power of attorney, or

  2. are exercisable by a person under this Act where he reasonably believes that another person lacks capacity.

  1. In the case of an act done, or a decision made, by a person other than the court, there is sufficient compliance with this section if (having complied with the requirements of subsections (1) to (7)) he reasonably believes that what he does or decides is in the best interests of the person concerned.

  2. Life-sustaining treatment” means treatment which in the view of a person providing health care for the person concerned is necessary to sustain life.

  3. Relevant circumstances” are those—

  1. of which the person making the determination is aware, and

  2. which it would be reasonable to regard as relevant”.

There is significant case law considering best interests and it will always apply on a matter-by-matter basis. However, some useful general guidance was provided in the cases of Re G (TJ) [2010] EWHC 3005 COP and Re M (Statutory Will) [2011] 1 WLR 344 which, although both related to statutory will matters, consider at length the general issue of best interests.

In Re G(TJ), Mr Justice Morgan determined that best interests involves a number of factors, including:

  • the actual wishes of P

  • he beliefs and values which would be likely to influence P’s decision

  • other factors which P would be likely to consider if he had capacity to do so

  • a balance sheet of factors which P would draw up if he had capacity to do so.

Although Mr Justice Morgan accepted that there will be an element of substituted judgment, he emphasised that it is absolutely clear that the ultimate test for the court is the test of best interests and not the test of substituted judgment.

Extending the consideration of best interests, Mr Justice Munby in Re M stated:

  • there is no hierarchy between the various factors in section 4, that is, the best interests section of the MCA, beyond the overarching principle that what is determinative is the judicial evaluation of what is in P’s best interests.

  • the weight to be attached to the various section 4 factors will differ depending upon the individual circumstances of the particular case. A feature or factor which in one case may carry great, possibly even preponderant, weight may in another, superficially similar, case carry much less, or even very little, weight.

  • there may be one or more features or factors which are of magnetic importance in influencing or even determining the outcome.

  • P’s wishes and feelings will be a significant factor to which the court must pay close regard. The weight to be attached to those wishes and feelings will always be case specific and fact specific and in considering the weight and importance to be attached to P’s wishes and feelings the court must have regard to all the relevant circumstances. These circumstances include:

  1. The degree of P’s incapacity.

  2. The strength and consistency of the views expressed by P.

  3. The possible impact on P of knowing that his wishes and feelings have not been given effect to.

  4. The extent to which P’s wishes and feelings are, or are not, rational, sensible, responsible and pragmatically capable of implementation.

  5. The extent to which P’s wishes and feelings, if given effect, can properly be accommodated within the court’s overall assessment of what is in his best interests.

Mr Justice Munby also reiterated that best interests do not cease at the moment of death and this may extend to avoiding post-death litigation. This is particularly relevant when considering post-death arrangements (such as a statutory will).

It is not for the legal practitioner to generally consider best interests or make a judgment over the proposed course of action of an attorney or deputy (see further below where the client is considered to lack capacity), other than potentially raising a safeguarding concern. This concern may be raised with the Office of the Public Guardian, local authority or Police amongst others.

Contact detail for the Office of the Public Guardian’s safeguarding team are as follows:

  • Office of the Public Guardian


  • Telephone: 0115 934 2777

  • Textphone: 0115 934 2778

  • Monday to Friday, 9:30am to 5pm; Wednesday, 10am to 5pm

  • Office of the Public Guardian, PO Box 16185, Birmingham, B2 2WH

Section 1(6) Mental Capacity Act 2005: least restrictive option

The Mental Capacity Act Code of Practice explains the concept of least restrictive option as follows:

2.14 Before somebody makes a decision or acts on behalf of a person who lacks capacity to make that decision or consent to the act, they must always question if they can do something else that would interfere less with the person’s basic rights and freedoms. This is called finding the ‘less restrictive alternative’. It includes considering whether there is a need to act or make a decision at all.

2.15 Where there is more than one option, it is important to explore ways that would be less restrictive or allow the most freedom for a person who lacks capacity to make the decision in question. However, the final decision must always allow the original purpose of the decision or act to be achieved.

2.16 Any decision or action must still be in the best interests of the person who lacks capacity. So sometimes it may be necessary to choose an option that is not the least restrictive alternative if that option is in the person’s best interests. In practice, the process of choosing a less restrictive option and deciding what is in the person’s best interests will be combined. But both principles must be applied each time a decision or action may be taken on behalf of a person who lacks capacity to make the relevant decision”.


Mental Capacity Act 2005 principles: summary

      1. Presumption of capacity

      2. Assist the person to make the decision

      3. Cannot treat someone as unable to make a decision because they make an unwise decision

      4. Decisions must be taken in the person’s best interests

      5. Least restrictive option to be taken