Borton Petrini

California Law Regarding Expert Witnesses

There is no substitute for a law firm which employees experienced trial attorneys who are familiar with using law and motion to best represent their clients.  There are many types of motions which can be filed either to reduce the issues at trial, compel a party to act, to exclude evidence or witnesses at trial, or to challenge the testimony and opinions of expert witnesses.  Here we look at challenging an experts’ opinion and seeking to prevent or limit that expert’s testimony at trial.

The testimony of an expert can make or break your case.   In 1993 the US Supreme Court decided Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), establishing the federal Court standard for challenging the admissibility of the opposing party’s expert.  Federal Rules of Evidence Section 702 governs the testimony of expert witnesses offering opinions. Witnesses are qualified by “knowledge, skill, experience, training, or education” which allows them to testify in the form of an opinion. The Court looks at, a) whether the expert opinion will assist the trier of fact either to understand the evidence or make a fact determination which is an issue; b) whether the expert’s testimony is “based on sufficient facts or data”; c) whether the expert’s opinion is based on reliable principles and the methods used in coming up with the opinion; and, the principles and methods which were applied by the expert were in a manner that is reliable in the case at hand.  Most State Courts have adopted the Daubert standard to some extent. Trial attorneys need to understand the Daubert standards and if used properly, they can be a powerful tool for excluding expert evidence.

As to California, until 2012, California did not follow the federal Daubert standards regarding challenges to the admissibility of expert witnesses, but followed the “Frye-Kelly” rule, which held that expert testimony was admissible provided that it was of such a nature as to have received “general acceptance” in the scientific community. However, the California Supreme Court decided the case of Sargon Enterprises, Inc. v. University of Southern California, (2012) 55 Cal. 4th 747, which embraced a standard which is very close to the rule established in Daubert. The California Supreme Court explained: “Under Evidence Code section 801, the trial court acts as a gatekeeper to exclude speculative or irrelevant expert opinion.  The expert’s opinion may not be based on assumptions of fact without evidentiary support, or on speculative or conjectural matters.  The exclusion of expert opinions that rest on guess, surmise or conjecture is an inherent corollary to the foundational predicate for admission of the expert testimony…”  The question the trial Court looks to answer is, will the testimony assist the trier of fact to evaluate the issues it must decide?

Filing a motion seeking to challenge an opposing party’s expert can be a deciding factor in a case.  As such, the experienced trial attorneys at Borton Petrini, LLP work diligently and understand the law and motion practice to achieve the best possible result for their clients.



Jeff Dains is a Partner in our San Bernardino office and practices in business litigation, construction law and real estate law.



Legal Disclaimer: This article is designed for general information only. The information presented should not be construed to be formal legal advice, nor the formation of a lawyer/client relationship.

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