California Trial Judges' Gatekeeping Changes for Expert Witnesses


    In November 2012, the California Supreme Court in Sargon Enterprises, Inc. v. University of Southern California, 55 Cal. 4th 747 (2012), heightened California trial courts' gatekeeping role with regard to the admissibility of expert testimony. While arguably California trial courts have always had a duty to exclude speculative or unreliable expert testimony, practically, many courts have shied away from doing so believing that any problems with expert testimony should only go to the weight of the evidence, but not its admissibility. In a unanimous decision, the California Supreme Court in Sargon created an affirmative duty for a trial court to ensure a jury does not hear expert testimony based on unreasonable comparisons or opinions not supported by the materials on which the expert purports to rely, or otherwise speculative.

    History of Admissibility of Expert Testimony in California

    In 1923, the District of Columbia Courts of Appeal in Frye v. U.S. (1923) 293 F.1013, set forth a standard that required a proponent of scientific expert testimony to show the expert opinion proceeded from a scientific principle that is sufficiently established to have gained general acceptance in the field in which it belongs. In 1976, the California Supreme Court in People v. Kelly (1976) 17 Cal. 324, adopted the test set forth in Frye and created a three-part test to determine the foundational reliability of the scientific evidence:

    • Reliability of the method must be established;
    • Witness furnishing testimony must be properly qualified as an expert to give opinion on the subject;
    • Proponent of the evidence must show the correct scientific procedures were used in the particular case.

    As a result, California has been coined as a Kelly/Fyre state regarding admissibility of expert testimony and has been rather permissive in allowing expert testimony. Generally, so long as the expert can describe a scientific method used in arriving at a conclusion, the court's job in screening for reliability is done. Indeed, this differs greatly from the current federal admissibility standard set forth in Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) 509 U.S. 579, and Kumho Tire Co. v. Carmichael (1999) 526 U.S. 137 — finding that a trial judge must act as a gatekeeper to ensure that any and all scientific testimony or evidence admitted is not only relevant, but also reliable.

    In recent years prior to Sargon, there has been a considerable conflict in California law concerning the extent of a trial court's responsibility to assess the foundation of expert opinion testimony. On one hand, Evidence Code § 801(b) requires that an expert opinion be based on matter "that is of a type that reasonably may be relied upon by an expert in forming an opinion upon the subject to which his testimony relates." And, on the other hand, California appellate courts have found that it is improper for trial courts to evaluate the studies that form the basis for an expert's opinion as a threshold to admitting an opinion.

    The Sargon decision goes a long way in resolving this conflict by specifically embracing Evidence Code § 801(b) and solidifying that trial courts have a "substantial 'gatekeeping' responsibility" under the Evidence Code to exclude unreliable and/or speculative expert opinion testimony. Sargon Enterprises, Inc. v. University of Southern California, 55 Cal. 4th at 769.

    Gatekeeper Role for Trial Courts After Sargon

    In finding that a trial court has a gatekeeping duty to keep out unreliable and speculative expert testimony, the Supreme Court in Sargon found that this duty extends from both Evidence Code § 801(b) and § 802, and that according to these Evidence Code sections, "the matter relied upon must provide a reasonable basis for the particular opinion offered, and that an expert opinion based on speculation and conjecture is inadmissible." Id. Therefore, concluding that, "[u]nder Evidence Code sections 801, subdivision (b), and 802, the trial court acts as a gatekeeper to exclude expert opinion testimony that is (1) based on matter of a type on which an expert may not reasonably rely, (2) based on reasons unsupported by the material on which the expert relies, or (3) speculative. Other provisions of law, including decisional law, may also provide reasons for excluding expert opinion testimony." Id.

    What Happens Now

    While the true implications of the Sargon decision remain to be seen, taken broadly, the decision will make unreliable and speculative expert testimony that previously would have reached a jury, now inadmissible. The California Supreme Court's clarification of the interaction between Evidence Code § 801 and § 802 brings California closer to the federal admissibility standard and allows trial courts to exclude unreliable and speculative evidence not only on methodology, but also on the reasoning and foundation for the expert's opinion.

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