Greenman v. Yuba Power Products, Inc.

William Greenman received a Shopsmith combination power tool as a gift from his wife. He used it as a lathe to make a chalice, and after using it several times, a piece of wood flew out of the machine and struck him in the forehead, causing serious injuries. Evidence showed that the set screws holding the tool's components were inadequate, making the tool defective.

Justice Traynor, fulfilling the vision of his Escola concurrence, reasoned that the purpose of strict liability is to ensure that the costs of injuries resulting from defective products are borne by the manufacturers who put those products on the market rather than by the injured persons who are powerless to protect themselves. He rejected the contract-based warranty framework as inadequate, noting that warranty law's notice requirements and privity limitations created unjust barriers to recovery. The court grounded liability in tort principles, making it clear that the manufacturer's duty runs to all foreseeable users, not just those in privity of contract.

Greenman triggered one of the most rapid doctrinal shifts in American legal history. Within a few years, the American Law Institute adopted Section 402A of the Restatement (Second) of Torts, imposing strict liability on sellers of defective products. Nearly every American jurisdiction adopted some form of strict products liability. The case fundamentally changed the relationship between manufacturers, consumers, and the tort system, creating the modern products liability regime.