ABSTRACT
Issues about capacity frequently arise in three groups of patients: children and adolescents, patients with learning difficulties, and patients with mental illness. A person has capacity so long as he has the ability to understand and retain relevant information for long enough to reach a reasoned decision, regardless of the actual decision reached. An adult person should be presumed to have the competence to make a particular decision until a judgement about capacity can be made. This judgement can only be made about present capacity, not about past or future capacity, and it should only be made for a specific decision, as different decisions require different levels of capacity. If capacity is lacking or cannot be established (e.g. in an emergency situation), the doctor in charge has the responsibility to act in the best interests of the patient, although it is good practice for him to involve colleagues, carers, and relatives in the decision-making. In difficult situations or if there are differences of opinion about the patient’s best interests, the doctor should consult a senior colleague or seek legal advice.
