84 The ruling of the trial judge was plainly correct. The evidence given on the voir dire established that there are two related fields of expertise. The first, which is primarily the province of the psychiatrist, is the field of behavioural disorders arising from dissociative mental states, including those associated with parasomnia and somnambulism. The second, which is primarily the field of the respiratory physician, is the diagnosis and treatment of sleep disorders including sleep apnoea and other abnormal conditions associated with sleep. Dr Varghese is relevantly qualified in the former field of expertise. The fact that he was not qualified in the latter, and could not, himself, undertake the work of diagnosis and treatment undertaken by a respiratory physician, did not mean that the opinions he expressed on the mental states associated with somnambulism, and the behavioural characteristics of those who experienced sleepwalking, were not admissible. Issues arising from the existence of another field of expertise in which Dr Varghese was not qualified, or the extent of his experience in the field of sleep disorders generally, or arising from his attitude to the classification manuals available for use by medical practitioners were all questions properly taken into account by the jury when assessing the weight to be given to his evidence. However, they were not issues that went to the admissibility of his evidence.