In what circumstances will the court admit or deny testimony from an expert psychologist in a criminal case?

In People v. Page (1991) 2 Cal.App.4th 161 (Page), the court was faced with circumstances closely analogous to those in the case at hand. In Page, the defendant was tried for murder, based in part on a confession he had given to the police. The trial court admitted the testimony of an expert psychologist for the defense, concerning factors that can make a person vulnerable to suggestion and lead him to give an inaccurate statement in an interrogation setting. But much like the challenged ruling in the case at hand, the court excluded the expert's proffered testimony specifically relating these principles to the statements the defendant had given to the police, and expressing his opinion concerning the confession's reliability in light of the circumstances shown by the evidence. (Id. at p. 179.) On appeal, the court affirmed the exclusion of that testimony.