What Makes a Product Legally Defective in California

When a product causes an injury, the legal question is not simply whether something went wrong. California law asks a more specific question: what kind of defect was it? The answer determines who can be held responsible, what has to be proven, and how the claim is built. California recognizes three categories of product defects, and a single product can involve more than one.

A manufacturing defect exists when the product that injured you was not made the way it was supposed to be made. The design may have been perfectly safe, but something went wrong on the assembly line, in the materials, or during assembly. The item that reached you differs from the manufacturer's intended product, and that difference is what made it dangerous.

Examples include a batch of medication contaminated during production, a welded joint on a vehicle bracket that was improperly fused, or a battery cell with an internal short caused by a crimping error. In each case the design is sound, but the specific unit that reached the consumer was not built to specification.

A design defect exists when every unit is built exactly as intended, and the design itself is the danger. The product is unreasonably dangerous as designed, regardless of whether it was manufactured correctly. This is where California law gives injured consumers two independent routes to prove liability under the California Supreme Court's decision in Barker v. Lull Engineering Co.

• The consumer-expectations test: the product failed to perform as safely as an ordinary consumer would expect when used in an intended or reasonably foreseeable way.
• The risk-benefit test: the risk of danger inherent in the design outweighs the benefits of that design. Once the injured person shows the design caused the harm, the burden shifts to the manufacturer to justify the design choices it made.

Either route is sufficient. A design defect case often involves engineering analysis, alternative design options, and testing records, which is why early evidence preservation matters so much.

A failure to warn, sometimes called a marketing defect, exists when the product carried a known risk that adequate instructions or warnings could have addressed, and the company sold it without those warnings. The product itself may be well-designed and well-manufactured, but the absence of meaningful warnings made it unreasonably dangerous.

This category covers prescription drugs whose side effects were not disclosed, power tools sold without guards or cautions, and consumer products that carry hidden fire or chemical risks. The question is not whether the manufacturer knew about the risk, but whether the warnings that accompanied the product were adequate for a reasonable consumer.

Strict liability means an injured person generally does not have to prove the manufacturer was careless. But strict liability still requires proving that the product was defective, that the defect existed when it left the manufacturer's control, and that the defect caused the injury. Identifying which type of defect applies shapes what evidence needs to be preserved, what experts should be retained, and what the claim ultimately looks like.

This article is general information, not legal advice, and does not create an attorney-client relationship. If a product injured you or someone in your family, the specific facts of your situation determine which category applies and what your options are.