What is the legal theory that holds a product manufacturer liable without proof of negligence?

The legal theory is strict liability, under which a product manufacturer may be liable for harm caused by a defective product without proof of negligence. The focus is on the product’s defect and its connection to the injury, rather than on whether the manufacturer acted carelessly.

In a typical product-liability claim, the plaintiff must establish that the defendant made, distributed, or supplied the product; that the product was defective; that the defect caused the injury; and that damages resulted. Defects are commonly classified as manufacturing defects, design defects, or inadequate warnings and instructions.

Modern American strict-products-liability doctrine is strongly associated with Greenman v. Yuba Power Products, a 1963 California Supreme Court decision. It built on earlier developments such as MacPherson v. Buick Motor Co. in 1916, which weakened the old requirement that an injured person must have a direct contractual relationship with the manufacturer.

Strict liability is not automatic liability for every product-related accident. A plaintiff still must prove defect, causation, and harm, and manufacturers may raise defenses such as misuse, alteration, or the absence of a defect. Breach of warranty and negligence remain separate product-liability theories.