Part-Persons who lack capacity (10) "Life-sustaining treatment" means treatment which in the view of a person providing health care for the person concerned is necessary to sustain life. (11) "Relevant circumstances" are those-(a) of which the person making the determination is aware, and (b) which it would be reasonable to regard as relevant. 5 Acts in connection with care or treatment (1) If a person ("D") does an act in connection with the care or treatment of another person ("P"), the act is one to which this section applies if-(a) before doing the act, D takes reasonable steps to establish whether P lacks capacity in relation to the matter in question, and (b) when doing the act, D reasonably believes-(i) that P lacks capacity in relation to the matter, and (ii) that it will be in P's best interests for the act to be done. (2) D does not incur any liability in relation to the act that he would not have incurred if P-(a) had had capacity to consent in relation to the matter, and (b) had consented to D's doing the act. (3) Nothing in this section excludes a person's civil liability for loss or damage, or his criminal liability, resulting from his negligence in doing the act. 11 Lasting powers of attorney: restrictions (1) A lasting power of attorney does not authorise the donee (or, if more than one, any of them) to do an act that is intended to restrain P, unless three conditions are satisfied.