The plaintiff, an individual who developed an asbestos-related disease after years of workplace exposure to asbestos-containing insulation products, sued multiple manufacturers, including Owens-Corning Fiberglas Corporation, under theories of strict products liability for failure to warn. At trial, Owens-Corning sought to introduce evidence of the state of scientific and medical knowledge during the years of the plaintiff's exposure, contending that the specific risks alleged were not generally recognized or knowable by the prevailing scientific community at that time. The trial court, however, excluded most of this "state-of-the-art" evidence as irrelevant on the theory that strict liability for failure to warn does not depend on a manufacturer's knowledge or fault, and instructed the jury accordingly. The jury returned a plaintiff's verdict on the failure-to-warn claim. On appeal, the central question became whether, in a strict liability failure-to-warn case, the trier of fact may consider what risks were known or knowable at the time of manufacture and distribution, and whether evidence of the then-existing scientific knowledge is admissible for that purpose.
In a strict products liability failure-to-warn action, must the plaintiff prove that the product's risk was known or knowable in light of the generally recognized and prevailing best scientific and medical knowledge at the time of manufacture and distribution, and is state-of-the-art evidence admissible to establish what was known or knowable?
Yes. In California, strict liability for failure to warn attaches only if the particular risk was known or knowable at the time of manufacture and distribution, in light of the generally recognized and prevailing best scientific and medical knowledge. Plaintiffs bear the burden to prove the existence of such a known or knowable risk, the manufacturer's failure to provide adequate warnings, causation, and damages. Defendants may introduce state-of-the-art evidence to show the limits of scientific and medical knowledge at the time, not to prove reasonableness of conduct per se, but to establish the absence of a known or knowable risk. This rule accords with Restatement (Second) of Torts § 402A comment j and California strict liability precedent distinguishing informational defects from design and manufacturing defects.
The California Supreme Court held that in strict liability failure-to-warn cases, the risk must have been known or knowable at the time of manufacture and distribution. Evidence of the state of scientific and medical knowledge at the relevant time—state-of-the-art evidence—is admissible to determine whether the risk was known or knowable.
The Court reconciled California's strict liability doctrine with the nature of informational defects. Unlike manufacturing or design defects, where the product's condition can be judged without regard to the manufacturer's knowledge, a duty to warn presupposes that the manufacturer knew or reasonably should have known of the risk. The Court drew on Restatement (Second) of Torts § 402A comment j, which conditions the duty to warn on knowledge or knowability through reasonable, developed human skill and foresight. It emphasized that requiring proof of knowability does not collapse strict liability into negligence: the inquiry remains product-focused (was an adequate warning provided for a risk that was known or knowable?) rather than conduct-focused (was the manufacturer reasonable?). Thus, the reasonableness of defendant's behavior remains irrelevant except insofar as it bears on whether a risk was generally recognized by the scientific community at the time. The Court rejected the argument that strict liability for failure to warn should be absolute regardless of knowability, reasoning that imposing liability for unknowable risks would be both unsound policy and inconsistent with precedent. It noted that California cases had already recognized limits on strict liability (e.g., prescription drug cases and design defect balancing) and that knowledge or knowability is inherent in the warning function. On evidentiary questions, the Court held that state-of-the-art evidence is admissible because it directly informs whether a risk was knowable; excluding such evidence would preclude the jury from assessing a necessary element. At the same time, the Court cautioned that the evidence is not a license to relitigate the reasonableness of corporate conduct, but is limited to what the generally recognized and prevailing scientific knowledge was at the time. Concluding that the trial court's exclusion of such evidence improperly prevented the jury from deciding a material element of the claim, the Court approved admission of state-of-the-art evidence and required conformity with the knowability standard.
Anderson crystallizes a core principle of modern products liability: in failure-to-warn cases, strict liability is not absolute and turns on the state of knowledge at the time of manufacture and distribution. It gives plaintiffs and defendants clear burdens—plaintiffs must show the risk was known or knowable; defendants may counter with state-of-the-art evidence. The case guides jury instructions, motions in limine, and expert proof in toxic torts and other warning cases. For law students, Anderson is essential for understanding how California harmonizes strict liability with practical and evidentiary constraints, distinguishes failure-to-warn from design/manufacturing defects, and aligns with Restatement comment j. Its reasoning reverberates through later California cases addressing pharmaceuticals and complex product risks.
Anderson v. Owens-Corning Fiberglas strikes a careful balance in strict products liability by recognizing that, for informational defects, a duty to warn exists only if the risk was known or knowable at the time of manufacture and distribution. By admitting state-of-the-art evidence, the Court ensures that juries decide failure-to-warn claims based on the scientific landscape contemporaneous with the product's circulation, not through hindsight.