Gatekeepers and Keymasters: Admissibility of Expert Testimony at Trial

Author: Daniel Fallon

While juries play a most significant role in the outcome of litigation, we all know cases often come down to a battle of the experts. Stretching credulity under a shield of impressive credentials, experts often make unfounded leaps and bounds in an attempt to sway the impressionable minds of jurors. To protect jurors and parties from speculation disguised as reasoned expert opinion, the California Supreme Court issued its game-changing opinion in Sargon Enterprises, Inc. v. University of Southern California (2012) 55 Cal. 4th 747.

Sargon established the trial judge as the “gatekeeper” to exclude improper expert opinion testimony. The seminal decision now requires defense counsel to be the “keymaster” helping the court lock down unsupported opinions of its opponent, while opening the door for its own experts’ testimony based on proper foundation to reach sound conclusions.

In Sargon, the plaintiff had created and patented a dental implant to be used in reconstructive surgery and compete with bigger players in the field. Prior to being placed on the market, the plaintiff contracted with the University of Southern California School of Dentistry to conduct a clinical trial of the product to determine its efficacy and competitive nature in the market. However, USC failed to complete the clinical study and the plaintiff was unable to market the product as anticipated. It sued USC for breach of contract and sought significant damages representing future profits the plaintiff claimed it would have realized but for the failure of the clinical trial.

In its decision, the unanimous California Supreme Court upheld the exclusion of expert testimony on lost profits as speculative and unreliable. In doing so, it evaluated the history of state and federal law on point, clarified the process of scrutinizing expert testimony, and established the trial court as the gatekeeper on such critical issues. The Court evaluated California Evidence Code §§ 801(b) and 802 to hold, “the trial court acts as a gatekeeper to exclude expert opinion testimony that is (1) based on a 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.” (At 771-772.)

Of importance to defense counsel, Sargon invests trial courts with an affirmative duty to preclude the introduction of expert testimony not based on reasonably reliable material, or otherwise reaching conclusions unsupported by reasonably reliable material. At its essence, Sargon intends to protect jurors, and by extension parties, from trials being decided upon baseless speculation in the guise of sound expert opinion. Accordingly, it is up to counsel to remind the trial judges of their new role as gatekeepers, and request them to carefully scrutinize opposing expert opinions within the guidelines of Sargon.

At the pre-trial motion in limine stage, counsel should challenge any opposing opinions that do not appear supported by information regularly relied upon by experts in that field. Likewise, challenges should be made to any opinions that substantively diverge from the conclusions otherwise reasonably reached by the information the expert relied upon. In support of such motions, counsel should cite to the vast body of federal case law on point, as the California decision of Sargon similarly cites federal authorities and is a natural outgrowth of the interpretation of the Federal Rules of Evidence in such seminal cases of Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) 509 U.S. 579, and Kumho Tire Co. v. Carmichael (1999) 526 U.S. 137.

Finally, as this is a battle of the experts, counsel should rely heavily on its own experts in finding and exposing the holes in the opinions and foundational materials of their opposing experts. In order to facilitate the trial judges’ new role as “gatekeepers” under Sargon, counsel must act as the “keymaster” to lock down any speculative expert opinions from the opposition and unlock its own reasoned expert testimony for the benefit of the jury.


Mr. Fallon specializes in civil litigation in the areas of professional liability. He has significant experience executing litigation strategies to the benefit of his individual and corporate clients. Contact Dan at 858.263.4132 or

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