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3 August 20234 minute read

SB 652 signed into law: Product manufacturers face new challenges in California

A change to the California Evidence Code will go into effect next year making it more difficult for pharmaceutical and other product defendants to admit expert testimony regarding alternative causes of a plaintiff’s injury.

On July 13, 2023, Governor Gavin Newsom signed California Senate Bill 652, which adds to Evidence Code Section 801 governing expert testimony. Under existing law, the plaintiff has to prove by a reasonable degree of medical probability that his or her injury was caused by the defendant’s product. Currently, because the defense does not carry the burden of proof, the defense’s expert may testify about other, unrelated causes of injury without meeting the reasonable degree of medical probability standard.

SB 652 was sponsored by the Consumer Attorneys of California, an organization that “stand[s] for plaintiffs seeking accountability from those who do wrong.”[1] The bill was explicitly drafted to abrogate the decision in Kline v. Zimmer, Inc. (2022) 79 Cal.App.5th 123, where the California Court of Appeals held that, because the burden of proof ultimately lies with the plaintiff, a defense expert need not show that an alternative cause was more likely than not the cause of the plaintiffs injuries.

In Kline, the plaintiff was implanted with an artificial hip joint manufactured by Zimmer, Inc. The surgery was unsuccessful, and Kline then sued Zimmer on a products defect theory. At trial, the court excluded Zimmer’s proffered expert testimony regarding possible explanations of Kline’s persistent pain because they were expressed to less than a reasonable medical probability. In contrast, the trial court allowed Kline’s expert to testify that Zimmer’s defective product caused Kline’s symptoms to a reasonable degree of medical probability.

The jury returned a verdict for Kline. The Court of Appeal reversed and remanded for a trial on causation, holding that Zimmer was entitled to introduce expert testimony regarding possible (albeit not probable) explanations for Kline’s symptoms to show that Kline had failed to satisfy his burden of proving that Zimmer caused Kline’s injuries. The court explained that to “withhold such information from the jury is to deprive it of relevant information in assessing whether the plaintiff has met its ultimate burden of persuasion.”[2]

Next year, Evidence Code 801 will hold a defendant’s expert to the same medical causation standard. As amended, Section 801.1, will state:

(a) Where the party bearing the burden of proof proffers expert testimony regarding medical causation and where that party’s expert is required as a condition of testifying to opine that causation exists to a reasonable medical probability, the party not bearing the burden of proof may offer a contrary expert only if its expert is able to opine that the proffered alternative cause or causes each exists to a reasonable medical probability, except as provided in subdivision (b).

(b) Subdivision (a) does not preclude a witness testifying as an expert from testifying that a matter cannot meet a reasonable degree of probability in the applicable field and providing the basis for that opinion.

Practical implications

Next year, Kline will be abrogated to a large extent, if not entirely. Defendants must then prepare their experts with evidence to opine to a reasonable degree of medical probability regarding alternative causation. For example, an expert who will testify that a plaintiff’s cancer was caused by genetics, diet, or other environmental factors – as opposed to a pharmaceutical drug – will now have to support this opinion with case-specific facts and material reasonably relied on by other experts in the field, such as epidemiology or peer-reviewed studies. Extensive discovery must be undertaken to obtain a complete medical and social history. Research should be done to confirm that the alternative theory of causation is generally accepted in the scientific or medical community. Defendants will have to plan early on how frame their defense around alternative sources of causation.

However, there may be other ways to admit evidence on alternative cause. Evidence Code 801.1 subsection (b) clarifies that a defense expert is not precluded from opining that the plaintiff-expert’s opinion failed to adhere to a reasonable degree of scientific certainty as would be accepted in the applicable field, by, for example, failing to investigate and rule out alternative causes of injury.

The upcoming changes to Evidence Code 801 are significant. Practitioners will have to be more strategic and more prepared if they are to rise to the increased evidentiary standards SB 652 will impose on defense medical experts.

To find out more about the implications of these changes for your business, please contact either of the authors or your DLA Piper relationship partner.



[2] Kline v. Zimmer, Inc. (2022) 79 Cal.App.5th 123, 133–34, review denied (Aug. 31, 2022).