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Written on 3rd March 2021 by It's the Principle!

What are the five principles of the Mental Capacity Act 2005?

Before considering the principles of the Mental Capacity Act, it’s worth understanding what mental capacity is. 

Mental Capacity is someone’s ability to make everyday decisions. This is often referred to as a person’s right to Autonomy, the ability to make up one’s own mind on decisions about what to do rather than being influenced by someone else or being told what to do. Sounds simple so far and because of which it is often taken for granted.

The problem begins when you are asked to determine whether someone lacks the mental capacity to make their own decisions. In some cases it is fairly straight forward. Someone who is unconscious or in a coma is clearly unable to make decisions themselves. Most cases are not quite so straight forward, due to the issue of capacity being as a result of an impairment of, or disturbance in, the mind. 

In England and Wales the legal framework for deciding if someone lacks the mental capacity to make their own decisions is governed by the Mental Capacity Act 2005 (“the Act”).

Section 1 of the Act outlines the five ‘statutory principles’ that underpin the legal requirements when determining whether someone lacks capacity. The aim of the principles is to ensure that before a decision is taken out of their control, every opportunity to maximise their ability to make the decision, or participate in the decision themselves, is made. In other words people need to be given the opportunity to try and make their own decisions first.


“A person must be assumed to have capacity unless established that he lacks capacity” (section 1(2)). 

Everyone who is over the age of 16 should be considered to be able to make their own decisions. This was a fundamental principle of common law, the presumption of capacity, before being laid out in the Act that every adult has the right to make their own decisions. Even if someone has an impairment it does not necessarily mean that they cannot make the decision themselves in the first place – unless there is proof to the contrary.

They key part here is proof, unless it can be shown someone lacks the capacity to make a particular decision it should be assumed that they can make the decision for themselves. 

The exception to this is if someone is under 16, where the general presumption is that, due to their age, they are incapable of making decisions on their own. In these circumstances, if there is a need to assess the capacity of a child the determination is whether they are likely to have capacity at 18 in respect of the decision to be made (section 18(3)).


“A person is not to be treated as unable to make a decision unless all practical steps to help him to do so have been taken without success” (section 1(3)).

The aim here is to prevent people who need support in making decisions from being automatically labelled as lacking capacity.

It is important to ensure that all practical steps are taken to help someone make their decision before concluding that they lack capacity (section 4(4)). The kind of support will differ from person to person, depending upon their individual circumstances. For instance, if you know that a person has difficulties making decisions first thing in the morning but is more alert later on in the day then you should wait until later to discuss the decision to be made. Another way to assist with decision making is to use props or pictures. The key here is to assist the person to make their own decisions without unnecessary intervention

It is worth mentioning that the decision reached does not always have to be affirmative. Rejection of a particular choice is still a decision. Anyone supporting someone to reach a decision must not act in a manner that may put ‘undue pressure’ on them or seek to influence the decision.


“A person is not to be treated as unable to make a decision merely because he makes an unwise decision” section 1(4)). 

Everyone has the right to live their own life and make decisions based on their own personal beliefs, experience and preference. Just because a decision might be objectively considered unwise does not necessarily mean that they lack capacity.

It is established that, as a species, we learn from our mistakes and it is just as important that we are allowed the opportunity to make those mistakes for ourselves so that we can develop. 

An unwise decision may have its own justifications. For instance a person may need ongoing medicial intervention and therapy but instead they choose to go on holiday and decline the medical intervention and therapy so as to enjoy themselves and support their mental health. To them this is more important although they appreciate they will not have the medical intervention and therapy during that period.

Although an unwise decision, or even a couple of unwise decisions, is not proof that someone lacks capacity, it may be a cause for concern if there is a series of unwise decisions that are out of character and /or put them at risk.


“An act done, or decision made, under this Act for or on behalf of a person who lacks capacity must be done, or made, in his best interests” (section 1(5)).

This is a well-established principle in common law although it is not defined in the Act. However section 4 of the Act establishes a framework for what to consider when making a decision in a person’s best interest. These include not making a determination on capacity based on a person’s age or appearance as well as considering where possible a person’s past and present wishes, beliefs and values. One should also look to seek out the view of anyone who may know the person well such as a carer, parent, attorney or deputy.

Best interest is the core concept of making decisions for those lacking capacity. Consideration of their best interest must be made individually each time a decision is reached, regardless of whether a decision is similar to one made previously.


“Before the act is done, or the decision made, regard must be had to whether the purpose for which it is needed can be effectively achieved in a way that is less restrictive of the person’s rights and freedom of action” (section1(6)). 

The basic consideration here is whether the action justifies the restriction being made on a person’s ability to make their own decisions. This includes whether a decision should even be made at all.

The question here is whether it is possible to do something else that would interfere less with a person’s basic rights and freedoms. This is called the ‘less restrictive alternative’ and must still be in a person’s best interests. This could mean that you don’t choose the least restrictive option, as this would not be in their best interests

An example of how this principle could be applied is where a person with epilepsy has been advised to wear a protective helmet or be under close and constant supervision. It is then decided after an assessment that the person cannot make the decision himself although through his actions he makes it clear that he does not like to be closely supervised and enjoys his freedom. His carer and parents decide that a helmet is in his best interests and is the less restrictive alternative.

These five principles should to be considered each time a decision needs to be made on behalf of someone who may lack the capacity to make their own decisions, acting under the Act. By doing so, it allows for the appropriate action to be taken whilst carefully balancing the need to make a decision on someone’s behalf and their right to live their life their own way.

For more information about the Mental Capacity Act and how our Court of Protection team can help you please contact them by email at