There are three types of products liability cases: strict liability, negligence, and breach of warranty (which can be understood as a type of negligence). Each one reflects a different theory upon which a person injured by a product can recover. Developed by judges and part of the common law of states, the specific rules of each state vary, although many states have adopted the Model Uniform Products Liability Act. Both compensatory damages (monetary damages to compensate the plaintiff for harm caused by a defective product) and punitive damages (monetary damages to punish and deter conduct of the defendant) are available in products liability cases.

Strict Liability

Most products liability cases fall under strict liability. Strict liability is a legal principle that was developed by the California Supreme Court in the landmark decision, Greenman v. Yuba Power Products , Inc., 59 Cal.2d 57 (1963). Strict liability allows for a plaintiff to recover from an injury caused by a product without having to prove any misconduct of the defendant. A plaintiff need only prove injury by a defective product manufactured or sold by the defendant.

Some states no longer allow for strict liability. Currently, there is no comprehensive federal law on products liability; however, opponents to strict liability seek to eliminate strict liability through federal reform.

Negligence

It is much more difficult for a plaintiff to recover under a theory of negligence than strict liability. To do so, the plaintiff must establish the following: 1) that there was a relationship between the manufacturer and the plaintiff (specifically, that the manufacturer owed the plaintiff a duty of care, 2) a breach of the duty of care, 3) causing injury to the plaintiff.

In some circumstances, where negligence is otherwise particularly difficult to prove, courts apply a standard called negligence per se , or res ipsa loquitur . Negligence per se allows a plaintiff to establish the defendant's negligence by proving the defendant violated a relevant law. Res ipsa loquitur (meaning "the thing speaks for itself") allows a court to infer that the defendant was negligent due to certain circumstances, such as facts showing the injury can only be explained by the defendant's negligence.

Breach of Warranty

Breach of warranty is essentially a negligent failure by the defendant to warn the plaintiff of the dangers of the product. There are three types of a breach of warranty: 1) breach of the manufacturer or seller's express warranty, 2) breach of an implied warranty (provided that the product was not labeled with an "as is" or "with faults" disclaimer), and 3) breach of warranty of fitness of a product for a particular use (meaning, the defendant knew of the intended use by the buyer, who relied on the superior knowledge of the product by the defendant, who represented the product could be safely used in the manner intended by the buyer).