Plaintiff was injured while operating a Lull Engineering rough-terrain "high-lift" loader (a materials-handling machine with an extendable boom) at a construction site situated on a slope. Assigned to move heavy lumber across uneven ground, plaintiff—who had limited training and experience with the machine—attempted to transport a load with the boom elevated. The loader tipped on the incline, causing serious injuries. Plaintiff sued Lull on a strict products liability theory, alleging that the loader was defectively designed for foreseeable rough-terrain use because, among other things, it lacked adequate stabilizing features and/or mechanisms to mitigate tip-over risk, and that its warnings were insufficient. Lull defended on the grounds that the accident resulted from operator error and obvious terrain risks, and that the product's design was not defective when evaluated against then-existing engineering knowledge and its intended uses. At trial, the jury was instructed that plaintiff bore the burden of proving the design was defective in the sense that the risks outweighed the benefits. The jury returned a defense verdict, and plaintiff appealed.
In a strict products liability action alleging a defective design, what standards govern proof of defect, and which party bears the burden of proof under a risk–benefit analysis?
A design defect may be established by either of two alternative tests: (1) Consumer expectations test: A product is defective in design if it fails to perform as safely as an ordinary consumer would expect when used in an intended or reasonably foreseeable manner. (2) Risk–benefit test: A product is defective in design if, in light of relevant factors, the benefits of the challenged design do not outweigh its inherent risks. Once the plaintiff makes a prima facie showing that the design proximately caused injury while the product was used in an intended or reasonably foreseeable way, the burden shifts to the manufacturer to prove, in light of factors such as the gravity and likelihood of harm, feasibility of safer alternative designs, cost of alternatives, and adverse consequences of alternatives, that the benefits outweigh the risks. The plaintiff need not prove the existence of a safer alternative design as part of the prima facie case.
The California Supreme Court adopted the consumer expectations and risk–benefit tests as alternative means of proving a design defect and held that, once the plaintiff shows that the design proximately caused injury during intended or foreseeable use, the burden shifts to the manufacturer to establish that the benefits of the design outweigh its risks. Because the jury instructions improperly placed the risk–benefit burden on the plaintiff and otherwise conflated negligence concepts, the judgment was reversed and the case remanded for a new trial.
The court grounded its analysis in the policies of strict products liability articulated in Greenman and Cronin: spreading the costs of product-related injuries and incentivizing safer designs by assigning responsibility to manufacturers who are best positioned to reduce hazards. Requiring plaintiffs to prove, as an element of their case, that a design's risks outweigh its benefits would, in the court's view, drift back toward negligence by demanding proof of fault-like balancing that manufacturers control through their superior knowledge and records. To avoid this reintroduction of negligence concepts, the court allocated the burden of proving favorable risk–benefit to the manufacturer once the plaintiff shows that the design was a proximate cause of injury in intended or foreseeable use. Recognizing that some products are within the common understanding of consumers while others involve complex technical tradeoffs, the court endorsed two complementary tests. The consumer expectations test preserves Cronin's insight that ordinary users can form minimum safety expectations for many products; if those expectations are not met, the jury can find a defect without complex engineering proof. For more complex designs where lay expectations are not dispositive, the risk–benefit test provides a structured inquiry. The court listed relevant factors for the risk–benefit analysis, including the gravity of the danger, the likelihood of injury, the feasibility and cost of safer alternatives, and any potential adverse consequences of adopting such alternatives. Placing the burden of this analysis on the manufacturer aligns with information asymmetry realities and the deterrence goals of strict liability. The court also clarified that a plaintiff need not prove a feasible alternative design to establish a prima facie design-defect case; that evidence properly belongs within the manufacturer's burden to justify the chosen design under risk–benefit principles. Finally, the court rejected jury instructions that tethered liability to state-of-the-art knowledge as a complete defense or that imported negligence terminology, emphasizing that while feasibility and scientific knowledge are relevant to the risk–benefit calculus, strict liability does not turn on the manufacturer's due care but on the product's safety.
Barker is a cornerstone of California products liability law. It simultaneously preserves a straightforward, lay-oriented pathway to liability (consumer expectations) and establishes a rigorous, policy-sensitive framework (risk–benefit) for complex design disputes. Its burden-shifting rule is particularly influential: by requiring manufacturers to justify their designs once causation and foreseeable use are shown, Barker operationalizes strict liability's deterrence and loss-spreading goals and avoids collapsing design-defect cases into negligence. The decision frames modern jury instructions and has been elaborated in later cases (e.g., Soule v. General Motors) that define when consumer expectations suffice versus when risk–benefit analysis is necessary.
Barker v. Lull Engineering Co. crystallizes the modern approach to design-defect claims in California by offering two complementary tests and, crucially, by shifting the burden to manufacturers to defend their design choices once causation and foreseeable use are shown. This structure maintains the core of strict liability—focusing on product safety rather than fault—while equipping juries to evaluate complex technical disputes fairly.