(1)  For the purposes of this Act, an adult is taken to have the capacity to make a decision about his or her own assessment or treatment ( decision-making capacity ) unless a person or body considering that capacity under this Act is satisfied that –

(a) he or she is unable to make the decision because of an impairment of, or disturbance in, the functioning of the mind or brain; and

(b) he or she is unable to –

(i) understand information relevant to the decision; or

(ii) retain information relevant to the decision; or

(iii) use or weigh information relevant to the decision; or

(iv) communicate the decision (whether by speech, gesture or other means).

(2)  For the purposes of this Act, a child is taken to have the capacity to make a decision about his or her own assessment or treatment ( decision-making capacity ) only if a person or body considering that capacity under this Act is satisfied that –

(a) the child is sufficiently mature to make the d ecision; and

(b) notwithstanding any impairment of, or disturbance in, the functioning of the child's mind or brain, the child is able to –

(i) understand information relevant to the decision; and

(ii) retain information relevant to the decision; and

(iii) use or weigh information relevant to the decision; and

(iv) communicate the decision (whether by speech, gesture or other means).

(3)  For the purposes of this section –

(a) an adult or child may be taken to understand information relevant to a decision if it reasonably appears that he or she is able to understand an explanation of the nature and consequences of the decision given in a way that is appropriate to his or her circumstances (whether by words, signs or other means); and

(b) an adult or child may be taken to be able to retain information relevant to a decision even if he or she may only be able to retain the information briefly.

(4)  In this section –

information relevant to a decision includes information on the consequences of –

(a) making the decision one way or the other; and

(b) deferring the making of the decision; and

(c) failing to make the decision.