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Most of us are familiar with the issues which may arise when someone loses mental capacity to make decisions for themselves.  For solicitors, and other professionals representing those for whom mental capacity may be in doubt, the importance of ensuring a client's ability to provide clear instructions and engage with our advice, remains fundamental.  If a person is unable to make a decision for themselves, assistance may be required from another authorised to act on their behalf (for example, someone who holds a Lasting Power of Attorney), or from the Court.  


Decisions can range from the everyday – what to eat, what to wear, to more significant and life-altering decisions such as where to live, or whether to receive medical treatment.  Although the specific steps to be taken may vary according to the type of decision and its significance for the person concerned, the same legal framework applies to all assessments of mental capacity. Given the significant implications for individual liberty and autonomy, it is always important that those supporting people where questions or concerns arise around mental capacity, have a solid understanding of the key legal principles.  In the health and social care sector, the CQC will as part of its assessment framework, consider compliance with the Mental Capacity Act 2005 and its Code of Practice.  

The law governing what it means to have, or indeed to lose mental capacity, can be daunting to navigate both for professionals and those less experienced in this area. This article provides an overview of the approach to assessing someone's mental capacity to make a decision, and when those making a decision or providing support may wish to seek external advice.  

What does it mean to lack 'mental capacity'? 

Section 1 of the Mental Capacity Act 2005 (MCA 2005) sets out the core principles concerning mental capacity: 

  • A person must be assumed to have capacity unless it is established that they lack capacity (S.1(2));
  • A person is not to be treated as unable to make a decision unless all practicable steps to help them have been taken without success (S.1(3));
  • A person is not to be treated as unable to make a decision merely because they make an unwise decision (S.1(4)); 
  • 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 their best interests (S.1(5));
  • Before the act is done, or the decision is made, regards must be had 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 (S.1(6)). 

Each of these principles is a potential discussion topic, however the starting point is always a presumption that a person has capacity to make a decision.  This is the case unless it is established that it is 'more likely than not', that a person lacks capacity – but what does this mean?  

The law takes an 'issue specific' approach to mental capacity, rather than a 'status' approach.  This means that just because a person has a particular diagnosis or disability, is of a certain age or appearance, they are not to be automatically considered to 'lack capacity' to make decisions. Section 2(1) of the MCA states that someone lacks capacity in relation to a matter if: 

"at the material time he is unable to make a decision for himself in relation to the matter because of an impairment of, or a disturbance in the functioning of, the mind or brain" (emphasis added). 

The question of capacity is therefore time-specific (i.e. can the decision be made at that time– bearing in mind that for various reasons, someone may have fluctuating or temporarily incapacity).  It is also specific to the decision to be made, rather than the ability to make decisions generally. 

Section 3(1) of the MCA provides that a person is unable to make a decision if (because of an impairment of / disturbance in the functioning of, the mind or brain) they are unable:- 

(a) to understand the information relevant to the decision, 
(b) to retain that information, 
(c) to use or weigh that information as part of the process of making the decision, or 
(d) to communicate his decision (whether by talking, using sign language or by any other means).

When should a capacity assessment be undertaken?

Applying the framework above, the assumption is that the supported person has capacity to make a decision unless it is established that they do not (on the balance of probabilities – 'more likely than not').  If there is reason to believe the person lacks capacity, then an assessment should be carried out to establish whether they are unable to understand the information relevant to the decision, retain that information, use or weigh it as part of the process of making the decision, or communicate it.  

Often, capacity is considered informally by professionals throughout the course of taking certain steps or actions (for example, solicitors should consider the capacity of their clients when receiving instructions, and care professionals when making care plan arrangements).     However, there may be a particular triggering event which necessitates further investigation, for example, if the person suffers a traumatic brain injury, or is undertaking medical treatment which is known to cause confusion. 

Some additional tell-tale signs that a person may require a capacity assessment may include: an unusual hesitation by the individual to make a decision (where they have previously not struggled with such decision), repeating questions which have already been answered and a display of inconsistent behaviours.   

If there are concerns as to a person's capacity, an assessment should be undertaken.  

Who can assess mental capacity?

In short – anyone.  It is the decision-maker who needs to be satisfied that a person lacks capacity.  In a care setting for example, this may be a care assistant providing support.  

Can they understand the information relevant to the decision?

What constitutes 'relevant information' will depend on the nature of the decision.  A person does not necessarily have to understand every element of what is being explained, but rather the 'salient factors'.  For example when a person makes a decision about when they will live, relevant information is likely to include [footnote – case ref LBX v K, L and M [2013] EWHC 3230 (Fam) per Theis J]: 

  • The type and nature of the options, what sort of properties are proposed, and any support to be provided;
  • The sort of area and any known risks;
  • The difference between living and visiting somewhere;
  • The available activities at each of the proposed options; 
  • How the person being assessed would see friends and family if they lived at each of the proposed options; 
  • The payment of rent and bills;
  • Any particular rules or restrictions and the general obligations under a tenancy; 
  • The sort of care / support they would receive at each option; 
  • Who they would be living with; 
  • The risk of friends or family members visiting less often if a certain placement is chosen. 

Conversely, information not considered relevant to such a decision includes: 

  • The cost of a placement (beyond a general understanding that payment will be required); 
  • The legal nature of the tenancy agreement / licence; 
  • Consequences of the living options in terms of the impact on a relationship with a friend or family member in the long-term (10-20 years). 

Can they retain the information? 

The question is then whether the person is able to retain the relevant information.  This is not memory test.  The person may only be able to retain the information for a short period only.  This is acceptable as long as they can retain for long enough to make the relevant decision, at the material time.   

Can they use or weigh the relevant information? 

This relates to a person's ability to engage with the decision-making process and to see the various factors being considered.  They do not have to be able to use and weigh every detail of the options presented, but again the most 'salient factors'.  When looking at the weight a person gives to the various factors affecting their decision, this is generally a matter for them, and may be influenced by their own values and beliefs.  However professional psychiatric input may be needed where it is unclear whether a person's failure to attach weight to a particular factor of the decision-making, is in fact an inability to weigh that information.  

Can they communicate their decision? 

This limb of the test was designed to address those cases where a person may be able to understand, retain and weigh the relevant information, but is unable to communicate their decision, despite all practicable steps being taken to support them.  

Does the person have an impairment or disturbance in the functioning of the mind or brain?

Although a formal diagnosis may assist with this point, it is not necessary.  An impairment or disturbance can include conditions causing confusion, drowsiness, or even the effects or alcohol or drug abuse (which may be temporary).  The decision-maker must have a reasonable belief that the person concerned lacks capacity to make the relevant decision.  If the decision relates to a more significant, non-routine health and welfare issue for example, the more important it may be to obtain expert medical evidence in support of a capacity assessment.   

Is the person's inability to make the decision because of the impairment or disturbance in the mind or brain? 

If this question can be answered in the affirmative, then the assessment will conclude that the person lacks capacity to make the decision in question, and a decision can instead be taken in their best interests (in accordance with section 4 MCA, outside the scope of this article).  In some cases, however, it may be unclear whether the inability to make decisions is due to the impairment or disturbance, or whether for example, they are being influenced by a third party.  

Those supporting people where mental capacity is in doubt, should ensure that they are familiar with the legal framework for assessing mental capacity.  Where significant and/or non-routine decisions are being contemplated on behalf of a vulnerable individual, those providing support should consider obtaining legal advice and/or input from medical or social work professionals, in particular where there are conflicting opinions as to which option would be in their best interests, or where there is suspected influence from third parties.  In any such cases, careful records should be kept of all capacity assessments and best interests decisions.