The discrepancy between the legal definition of capacity and the British Medical Association's guidelines.

T he emphasis in medical law and ethics on protecting the patient’s right to choose is at an all time high. Apart from circumscribed situations, for instance where the Mental Health Act 1983 is applicable, the only justification for medically treating an adult patient against his or her wishes is on the basis of common law, using the principle of best interests, and only when he or she lacks capacity to refuse treatment. As a result, it is important that clinicians should be able to assess capacity to refuse treatment. Given that judgements of incapacity involve deciding that a person does not have the ability to refuse treatment, a great deal of care needs to go into the assessment and characterisation of incapacity. There is divergence between the characterisation of capacity that is used by the courts and that which is recommended by the British Medical Association (BMA). The BMA usefully expands on the first element of capacity as set out in the standard legal definition of capacity in the Re C judgment but ignores the other two elements. By doing this, the BMA makes it unclear whether it is rejecting these as relevant to capacity; it also misses the opportunity to expand on these elements in a clinically useful way. We will begin with a description of the BMA’s advice and the standard English legal definition of capacity. 4 Then we will show that there are important discrepancies between these two sources of advice. We think that the BMA ought to clarify its position on capacity in order to safeguard the interests of physicians, healthcare workers, and patients.