PRODUCT LIABILITY | 2026-09-29
California Design-Defect Law: The Two Tests From Barker v. Lull Engineering
A California plaintiff harmed by a defectively designed product can prove the defect two ways — the consumer expectation test or the risk-benefit test. Barker v. Lull established both, and they change who bears the burden.
California is a strict products liability state: a manufacturer or seller can be liable for injuries caused by a defective product without proof of negligence. When the claim is that a product was <em>defectively designed</em>, California gives plaintiffs two distinct ways to prove the defect — the
When a product’s design causes injury, California law does not require the plaintiff to prove the manufacturer was careless — strict liability applies. But proving a design defect can be done two ways, and the difference matters.
Strict Products Liability in California
California recognizes strict liability for products that are defective in manufacture, design, or warnings. A manufacturer, distributor, or retailer in the chain of distribution can be liable for injuries caused by a defective product regardless of negligence. Design-defect claims are among the most complex, which is why California developed two tests to prove them.
The Two Tests From Barker v. Lull Engineering
In Barker v. Lull Engineering Co., the California Supreme Court held that a product may be found defective in design under either of two independent tests:
- The consumer expectation test. A product is defective in design if it failed to perform as safely as an ordinary consumer would expect when used in an intended or reasonably foreseeable manner. This test applies where the everyday experience of the product’s users permits a conclusion that the design violated minimum safety assumptions — it does not require expert testimony about the design’s risks and benefits.
- The risk-benefit test. A product is defective in design if the benefits of the challenged design do not outweigh the risk of danger inherent in it, considering factors such as the gravity of the danger, the likelihood of injury, the feasibility of a safer alternative design, the cost of an improved design, and the adverse consequences of an alternative.
The Burden Shift — Why the Risk-Benefit Test Matters
Barker’s most important procedural feature is the burden shift in the risk-benefit test. Once the plaintiff shows that the product’s design was a proximate cause of the injury, the burden shifts to the defendant to prove that the benefits of the design outweigh its risks. This is a significant advantage for plaintiffs: the manufacturer, which has the design information, must justify its design choices. The consumer expectation test, by contrast, keeps the focus on ordinary user expectations.
Which Test Applies
The consumer expectation test is generally reserved for cases where the product’s failure is within the common experience of ordinary consumers; for complex designs whose safety involves technical trade-offs beyond everyday experience, the risk-benefit test typically governs. In many cases the two tests are considered together, and California’s jury instructions (CACI) provide separate instructions for each.
Frequently Asked Questions
Do I have to prove the manufacturer was negligent?
No. California applies strict liability to defective products; you need not prove negligence, only that the product was defective and caused your injury.
What are the two design-defect tests?
The consumer expectation test (did the product perform as safely as an ordinary consumer would expect?) and the risk-benefit test (do the design’s benefits outweigh its risks?), from Barker v. Lull.
Who has the burden under the risk-benefit test?
Once the plaintiff shows the design was a proximate cause of injury, the burden shifts to the defendant to prove the benefits of the design outweigh its risks.
Which test applies to my case?
The consumer expectation test suits products within ordinary experience; complex designs typically use the risk-benefit test. Both may be considered together.
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Talk to a California Products Liability Attorney
If a defectively designed product injured you, California’s two design-defect tests — and the risk-benefit burden shift — can work in your favor. Trembach Law Firm handles California products liability claims. Call (818) 514-7680.
Contact Trembach Law Firm at (818) 514-7680 for a confidential consultation.
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