Competence and consent.
Savulescu J., Kerridge IH.
To perform a medical procedure on a competent patient who is refusing it may constitute battery; but to fail to perform a medical procedure on an incompetent patient who is refusing it may constitute negligence. Competence involves being able to understand the consequences of receiving medical treatment, and not receiving it, and being able to make a decision on the basis of that understanding. Competent people can sometimes make imprudent or irrational decisions. Cognitive impairment and mental illness do not necessarily render a person incompetent to consent to investigation and treatment. The suspicion of cognitive impairment or mental illness should prompt a thorough evaluation of competence and mental state. Treatment of incompetent people should be dictated by their best interests, advance directives or substituted judgement.