Medical treatment of those without capacity to consent Generally, it is the patient's (P’s) consent which makes invasive medical treatment lawful. Where P is unable to consent to treatment, it is lawful to give P treatment which is necessary in their best interests. Section 5 of the Mental Capacity Act 2005 (MCA 2005) provides a general defence for acts done in connection with the care or treatment of a person, provided that the actor has first taken reasonable steps to establish whether the person concerned lacks capacity in relation to the matter in question and reasonably believes both that the person lacks capacity and that it will be in that person’s best interests for the act to be done. In 2018, the Supreme Court confirmed in NHS Trust v Y that, if the provisions of MCA 2005 are followed, any relevant professional guidance observed and relevant guidance in the Code of Practice followed, including as to the undertaking of the decision-making process, then, if there is