Capacity, best interests, and lawful decision-making

In England and Wales, the Mental Capacity Act 2005 applies to people aged 16 and over who may lack capacity to make a specific decision. Scotland and Northern Ireland use different legal frameworks, but care staff across the UK still need the same careful habits: presume the person can decide, support their decision-making, avoid assumptions, and escalate when a decision may need formal review.

Having dementia, a learning disability, delirium, brain injury, mental illness, or communication difficulty does not automatically mean a person lacks capacity. Capacity is always about this decision, at this time.

The five Mental Capacity Act principles

• Presume capacity: start from the assumption that the adult can decide unless it is shown otherwise.
• Support the decision first: give all practicable help before deciding that the person cannot decide.
• An unwise decision is not enough: people can make choices others dislike without automatically lacking capacity.
• Best interests matter if capacity is lacking: any decision made on the person's behalf must be for them, not for staff convenience.
• Choose the least restrictive option: if action is needed, it should interfere as little as possible with the person's rights and freedom.

What assessing capacity means

Under the Mental Capacity Act, you first ask whether there is an impairment of, or disturbance in, the functioning of the mind or brain. If there is, you then ask whether that means the person cannot make the decision because they cannot:

• understand the relevant information
• retain it long enough to decide
• use or weigh it as part of the decision
• communicate their choice by any means

Frontline care staff are often the first to notice that a person may not be understanding or may have fluctuating capacity. Staff should follow local policy on who assesses and records capacity for different decisions, and should escalate more serious or disputed decisions promptly.

If a person may lack capacity, the first job is not to take control. It is to support the decision as far as possible, keep the assessment decision-specific, and use best interests only when needed.