s52(1)(b) = the abnormality of mental functioning must have substantially impaired D's ability to do one or more of the 3 things listed in s52(A):
(a) - understand the nature of his conduct
(b) - form a rational judgement
(c) - exercise self-control
R v Golds = Elias Li's judgement interpreted the term substantial to mean something which is more than merely trivial or minimal owing to the fact that it has a substance or something that is big or large