In Sargon Enterprises Inc. v. University of Southern California, the California Supreme Court clarified the standards that govern the admissibility of expert opinion testimony under California Evidence Code sections 801(b) and 802. As the Supreme Court explained, a trial court must act as “a gatekeeper” under sections 801(b) and 802 “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 an expert relies or (3) speculative.”

This gatekeeping obligation “means that a court may inquire into, not only the type of material on which an expert relies, but also whether that material actually supports the expert’s reasoning.” In what was a new development for California admissibility law, the Supreme Court’s decision also made plain that in conducting the foundational assessment required by the Evidence Code, trial courts should draw upon the scientific and technical evidence admissibility principles developed by the federal courts under Daubert v. Merrell Dow Pharmaceuticals Inc.

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