Synopsis
Assess capacity for one decision at the required time, maximise the person’s ability to decide, and make a defensible best-interests or overall-benefit decision only when the applicable legal threshold is met.
- Capacity is decision-specific and time-specific. Define the exact decision before assessing; a diagnosis, cognitive score, detention status or previous finding cannot answer the question by itself.
- Presume capacity and take practicable steps to support decision making: treat reversible factors, optimise timing, adapt communication, use an interpreter or communication aid, and reduce avoidable pressure.
- In England and Wales, apply the Mental Capacity Act 2005 diagnostic and functional test: an impairment or disturbance must make the person unable to understand, retain, use or weigh relevant information, or communicate the decision.
Reasoning priorities
State the choice, available options, timing and foreseeable consequences in concrete terms.
A finding for consent to surgery does not establish capacity for residence, finances or future treatment. Break compound decisions apart and avoid testing abstract knowledge that is not relevant to the choice.
Worked reasoning
An older inpatient with infection and fluctuating attention is asked to consent to a procedure that can safely wait until morning; she gives inconsistent accounts of its purpose and risks.
- Define the immediate decision and establish why capacity is in doubt, avoiding any broader conclusion about all decisions.
- Optimise decision making by treating delirium contributors, ensuring hearing aids and familiar communication, reducing noise and returning at the patient’s best time.
- Explain the options and assess understanding, retention, use or weighing and communication; document the patient’s own responses and the causal link to delirium.
- Final action: because delay is safe, defer the procedure and reassess rather than making an immediate substitute decision.
- Verification: reassess the same decision when attention improves, record the new findings and obtain consent only if the patient can then decide.