"A person must be assumed to have capacity unless it is established that they lack capacity."
"(3) A person is not to be treated as unable to make a decision unless all practicable steps to help her do so have been taken without success. (4) A person is not to be treated as unable to make a decision merely because he makes an unwise decision."
"(1) A person lacks capacity in relation to a matter if at the material time she is unable to make a decision for herself in relation to the matter because of an impairment of, or a disturbance in the functioning of, the mind or brain. (2) It does not matter whether the impairment or disturbance [in the functioning of the mind or brain] is permanent or temporary."
"A person is unable to make a decision for herself if she is unable - (a) to understand the information relevant to the decision, (b) to retain that information, (c) to use or weigh that information as part of the process of making the decision, or (d) to communicate his decision (whether by talking, using sign language or any other means)."