In People v. Russel (1968) 69 Cal.2d 187, the Court explained the question before the trial court is " whether, in light of the totality of circumstances revealed, it is necessary or proper that psychiatric knowledge in general be utilized in order to aid the trier of fact in its assessment of credibility. This decision must rest for the most part on the court's judgment as to whether an emotional or mental condition is involved which a body of laymen either would be unable to detect or would be unable to relate in terms of effect to the matter of credibility." ( Id., at p. 195.) Other relevant factors include considerations of time, expense, and the convenience of witnesses, as well as the court's own assessment of the accuracy of techniques and methods proposed to be utilized in the examination. ( Id., at p. 196, fn. 9.)