Capacity and Best Interests Decisions

Introduction

The Mental Capacity Act 2005 (MCA) is the statutory framework in England and Wales governing decisions made on behalf of, or with, people who may lack the mental capacity to make a particular decision themselves. It is central to geriatric medicine because cognitive impairment - from dementia, delirium, stroke or other causes - is common in this population, and clinicians frequently need to assess capacity and, where it is lacking, make lawful decisions in the person's best interests.¹

This is a heavily examined topic, both as a legal/ethical framework and as a practical clinical skill - the exam-relevant point is applying the Act's structured process correctly to a specific scenario, not simply reciting that 'capacity should be assessed'.

The five statutory principles

1. A person must be assumed to have capacity unless it is established that they lack it - the presumption of capacity
2. A person is not to be treated as unable to make a decision unless all practicable steps to help them do so have been taken without success
3. A person is not to be treated as unable to make a decision merely because they make an unwise decision - the right to make choices others disagree with
4. An act done, or decision made, for or on behalf of a person who lacks capacity must be done in their best interests
5. Before the act or decision, consider whether the purpose can be achieved in a way that is less restrictive of the person's rights and freedom of action

Assessing capacity: the two-stage test

Capacity is always decision-specific and time-specific - assessed for a particular decision, at the particular time it needs to be made, never as a global or permanent label. A person can lack capacity for one decision (e.g. managing complex finances) while retaining it for another (e.g. deciding what to eat), and capacity can fluctuate (e.g. with delirium) such that reassessment at a different time gives a different result.

Stage 1: diagnostic threshold

Is there an impairment of, or disturbance in the functioning of, the mind or brain? This can be permanent (dementia) or temporary (delirium, intoxication, severe pain or distress), and its mere presence does not by itself mean capacity is lacking - stage 2 must also be met.

Stage 2: functional test

Because of that impairment, is the person unable to do any one of the following in relation to the specific decision?

• Understand the information relevant to the decision, including the reasonably foreseeable consequences of deciding one way, the other, or not deciding at all
• Retain that information for long enough to make the decision (even briefly, if that is enough time to make and communicate it)
• Use or weigh that information as part of the process of making the decision
• Communicate the decision, by any means (talking, sign language, or any other means)

Supporting the person to make their own decision

Before concluding a person lacks capacity, all practicable steps to support their own decision-making must be tried: simplified or written information, involving a trusted family member, choosing the best time of day (particularly relevant with fluctuating conditions like delirium), using an interpreter or communication aid, and addressing reversible factors (treating pain, correcting a metabolic disturbance, allowing time for sedating medication to wear off) that might be temporarily impairing the person's ability to engage.

Making a best interests decision

Where a person is assessed as lacking capacity for a specific decision, any decision made on their behalf must be in their best interests - a structured process, not simply the clinician's own judgement of what is medically optimal.

• Consider the person's past and present wishes and feelings, including any written statement made when they had capacity
• Consider the beliefs and values that would be likely to influence the decision if they had capacity
• Consider other factors they would be likely to consider if able to do so
• Do not make the decision merely on the basis of the person's age, appearance, condition or behaviour
• Consult those who know the person where practicable and appropriate - family, carers, an attorney, or a deputy - and, where there is no one appropriate to consult and the decision is significant, involve an Independent Mental Capacity Advocate (IMCA)
• Consider whether the decision can be delayed until the person may regain capacity, where the decision is not urgent
• Choose the option that is least restrictive of the person's rights and freedoms while still achieving the purpose

Lasting Power of Attorney and advance decisions

Deprivation of Liberty Safeguards / Liberty Protection Safeguards

Where a person who lacks capacity is subject to continuous supervision and control and is not free to leave their place of care (for example, a locked dementia ward, or a care setting they are prevented from leaving even if they wished to), this constitutes a deprivation of liberty that requires legal authorisation - historically via the Deprivation of Liberty Safeguards (DoLS), being replaced by the Liberty Protection Safeguards (LPS) framework.²

This exists to ensure that restrictive care arrangements, even when made genuinely in a person's best interests, are subject to independent scrutiny and safeguards, and are the least restrictive option available - restricting liberty is never justified simply by clinical convenience.

Documenting a capacity assessment

A capacity assessment that is not documented is, in practical and medico-legal terms, one that did not happen. Good documentation records the reasoning, not merely the conclusion, and should allow another clinician to understand how the decision was reached.

1. The specific decision being assessed, in concrete terms - not 'capacity assessed' but 'capacity to consent to left total hip replacement'
2. The impairment identified at stage 1, and the evidence for it
3. The information given to the patient, including the risks, benefits and alternatives explained, and how it was presented
4. The steps taken to support the patient's decision-making - simplified language, written material, family present, timing, interpreter, hearing aids
5. Which of the four functional elements failed and why, quoting the patient's own words where they illustrate the reasoning
6. The conclusion, and if capacity is lacking, the best interests process followed and who was consulted

Emergency situations and fluctuating capacity

In a genuine emergency where a patient lacks capacity and there is no time to consult others or to establish their wishes, treatment necessary to save life or prevent serious deterioration can be given lawfully under the doctrine of necessity and section 5 of the Mental Capacity Act, provided it is in the person's best interests and no valid advance decision refuses it. This is a narrow provision - the urgency of the situation determines how much of the full best interests process is practicable, and it should not be used to bypass a process that time permits.

Fluctuating capacity - common in delirium, and also seen in dementia with Lewy bodies, epilepsy and some mental illnesses - requires assessing at the time the decision must be made and, where the decision can wait, deliberately choosing a moment when the patient is at their best. If a patient regains capacity, their own decision takes precedence over any best interests decision previously made on their behalf, and any such decision should be revisited rather than treated as settled.

Common pitfalls

• Assuming a diagnosis (e.g. dementia) automatically means a person lacks capacity for all decisions, rather than assessing decision-specifically
• Concluding incapacity because a decision seems unwise, rather than because the functional test is genuinely failed
• Failing to try practicable support measures before concluding capacity is lacking
• Treating 'best interests' as equivalent to the clinician's own view of the best medical outcome, without properly weighing the person's own wishes and values
• Restricting a person's liberty or freedom without recognising this requires formal legal authorisation

Summary

The MCA provides a structured, principled framework: presume capacity, support decision-making, assess capacity decision- and time-specifically using the two-stage test, and where capacity is genuinely lacking, make a best interests decision that gives real weight to the person's own values and wishes, using the least restrictive option available - a process, not a single judgement call.