“78. … The second question looks to whether there is a clear causative nexus between P's inability to make a decision for himself in relation to the matter and an impairment of, or a disturbance in the functioning of, P's mind or brain.” 44. In relation to the first question, the functional test, Lord Stephens JSC said at para 68 that as the assessment of capacity is decision-specific, “the court is required to identify the correct formulation of ‘the matter’ in respect of which it must evaluate whether P is unable to make a decision for himself”
“The correct formulation of ‘the matter’ then leads to a requirement to identify ‘the information relevant to the decision’ under section 3(1)(a) which includes information about the reasonably foreseeable consequences of deciding one way or another or of failing to make the decision: see section 3(4) .” 45. Lord Stephens JSC said at para 76 that, once the information relevant to the decision had been identified, then: “P is unable to make a decision for himself in relation to the matter ( section 2(1) ) if, for instance, he is unable to understand the information ( section3 (1)(a) ) or to use or weigh that information as part of the process of making the decision ( section 3 (1)(c) ).”
“38. It is important to note that section 3(1)(c) is engaged where a person is unable to use and weigh the relevant information as part of the process of making the decision. What is required is that the person is able to employ the relevant information in the decision-making process and determine what weight to give it relative to other information required to make the decision. Where a court is satisfied that a person is able to use and weigh the relevant information, the weight to be attached to that information in the decision-making process is a matter for the decision maker …” 47. In JB , it says: “If P is unable to make the decision his or herself in relation to the matter then the court moves to the second question namely whether the inability is ‘because of’ an impairment of, or a disturbance in the functioning of, P's mind or brain.”
‘.. the great safety net which lies behind all statute law and is capable of filling gaps left by that law, if and in so far as those gaps have to be filled in the interests of society as a whole. This process of using the common law to fill gaps is one of the most important duties of the judges. It is not a legislative function or process ... It is an essentially judicial process and, as such, it has to be undertaken in accordance with principle.’