Admissibility of Scientific Evidence in California

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. (Kelly, supra, 17 Cal.3d at p. 30.) The purpose of the rule is "to protect the jury from techniques which, though 'new,' novel, or ' "experimental," ' convey a ' "misleading aura of certainty." ' " (People v. Stoll (1989) 49 Cal.3d 1136, 1155-1156, quoting Kelly, at pp. 30-32.) The three-prong Kelly test requires (1) the reliability of the method be established by showing the technique has gained general acceptance in the particular field to which it belongs; (2) any witness testifying on general acceptance be properly qualified as an expert on the subject; and (3) the proponent of the evidence demonstrate that correct scientific procedures were used in the particular case. (People v. Venegas (1998) 18 Cal.4th 47, 78 (Venegas); Kelly, supra, 17 Cal.3d at p. 30.) The California Supreme Court explained the meaning of "general acceptance" under the first prong of the Kelly test: "Kelly 'does not demand that the court decide whether the procedure is reliable as a matter of scientific fact: the court merely determines from the professional literature and expert testimony whether or not the new scientific technique is accepted as reliable in the relevant scientific community and whether " 'scientists significant either in number or expertise publicly oppose a technique as unreliable.' " ' ' "General acceptance" under Kelly means a consensus drawn from a typical cross-section of the relevant, qualified scientific community.' " (People v. Soto (1999) 21 Cal.4th 512, 519.) General acceptance need not be established anew in each case. "Once a trial court has admitted evidence based upon a new scientific technique, and that decision is affirmed on appeal by a published appellate decision, the precedent so established may control subsequent trials, at least until new evidence is presented reflecting a change in the attitude of the scientific community." (Kelly, supra, 17 Cal.3d at p. 32; accord, Venegas, supra, 18 Cal.4th at p. 76.) Thus, a defendant is not foreclosed from showing that a scientific test has since been invalidated or that there has been a change in the consensus of the scientific community concerning the test. (People v. Allen (1999) 72 Cal.App.4th 1093, 1100-1101; People v. Smith (1989) 215 Cal.App.3d 19, 25.)