What is the "Kelly-Frye Rule"? (See People v. Kelly (1976) 17 Cal. 3d 24 and Frye v. United States (D.C. Cir. 1923) 293 F. 1013 54 App. D.C. 46, 34 A.L.R. 145.) In People v. Kelly (1976) 17 Cal. 3d 24, the California Supreme Court held the admissibility of expert testimony based on "a new scientific technique" requires proof of its reliability. (People v. Kelly, supra, 17 Cal. 3d at p. 30.) To satisfy this requirement, the proponent of the testimony must show: (1) the technique has gained general acceptance in the particular field to which it belongs; \(2) any witness testifying on general acceptance is properly qualified as an expert on the subject; (3) correct scientific procedures were used in the particular case. (Ibid.) "The Kelly test is intended to forestall the jury's uncritical acceptance of scientific evidence or technology that is so foreign to everyday experience as to be unusually difficult for laypersons to evaluate. . . . In most other instances, the jurors are permitted to rely on their own common sense and good judgment in evaluating the weight of the evidence presented to them. . . ." (People v. Venegas (1998) 18 Cal. 4th 47, 80.) One such instance involves the evaluation of expert psychological testimony, as illustrated in the recent case People v. Ward (1999) 71 Cal. App. 4th 368. There, the court considered whether psychiatric and psychological testimony relating to the defendant's propensity to repeat his sexually violent behavior was subject to Kelly-Frye. In deciding it was not, the court explained, " California distinguishes between expert medical opinion and scientific evidence; the former is not subject to the special admissibility rule of Kelly-Frye. . . . Kelly-Frye applies to cases involving novel devices or processes, not to expert medical testimony, such as a psychiatrist's prediction of future dangerousness or a diagnosis of mental illness. . . . Similarly, the testimony of a psychologist who assesses whether a criminal defendant displays signs of deviance or abnormality is not subject to Kelly-Frye. . . ." (Id. at p. 373.) There is good reason why courts draw a distinction between expert medical testimony and evidence derived from a new scientific device or procedure. "When a witness gives his or her personal opinion on the stand--even if he or she qualifies as an expert--the jurors may temper their acceptance of his or her testimony with a healthy skepticism born of their knowledge that all human beings are fallible. But the opposite may be true when the evidence is produced by a machine: like many laypersons, jurors tend to ascribe an inordinately high degree of certainty to proof derived from an apparently 'scientific' mechanism, instrument, or procedure. Yet the aura of infallibility that often surrounds such evidence may well conceal the fact that it remains experimental and tentative. Citation. " (People v. McDonald (1984) 37 Cal. 3d 351, 372-373.) McDonald is best known for sanctioning the use of expert testimony on the psychological factors relating to the reliability of eyewitness identification. Rejecting the notion a jury would be inclined to give undue credence to such testimony, the court observed, "We have never applied the Kelly-Frye rule to expert medical testimony, even when the witness is a psychiatrist and the subject matter is as esoteric as the reconstitution of a past state of mind or the prediction of future dangerousness, or even the diagnosis of an unusual form of mental illness." (People v. McDonald, supra, 37 Cal. 3d at p. 373.) The Supreme Court's reluctance to apply Kelly-Frye to expert psychological testimony was demonstrated once again in People v. Stoll (1989) 49 Cal. 3d 1136. In that case, the court found Kelly-Frye inapt to expert testimony regarding the defendants' propensity for sexual deviance. The court acknowledged Kelly-Frye theoretically could apply to " 'a new scientific process operating on purely psychological evidence.' " (Id. at p. 1156.) However, the court warned that "absent some special feature which effectively blindsides the jury, expert opinion testimony is not subject to Kelly/Frye." (Id. at p. 1157.)