In order for a plaintiff to recover damages in a product liability case, they must prove one or more of the following theories. Here is a concise explanation of the typical legal theories argued when a product causes personal injury.

Negligence

Negligence constitutes a lack of reasonable care in the manufacture or sale of a product, or the lack of adequate warning about the product.

The manufacturer owed a duty to the plaintiff, the manufacturer breached a duty to the plaintiff, the breach of duty was the actual cause of the plaintiff's injury, the breach of duty was also the proximate cause of the injury, the plaintiff suffered actual damages as a result of the negligent act.

Breach of warranty

Breach of warranty amounts to a failure to satisfy the terms of a promise regarding the product's operation or function.

The Uniform Commercial Code (U.C.C.), which has been adopted in part by every state and gives the basis for warranties in the United States.

First, the U.C.C. recognizes express warranties, where the seller represents the quality of the product. Next, the implied warranty of merchantability, is a promise that a product sold is in good working order and will do what it is supposed to do. Finally, the implied warranty of fitness for a particular purpose is a promise that a seller's advice on how to use a product will be correct.

Misrepresentation or "Tortious Misrepresentation"

Misrepresentation means giving consumers a deceptive sense of confidence in a product's safety.

A person has committed fraudulent misrepresentation, or deceit if he knew that a statement was false and intended to mislead the plaintiff by making the statement.

Also, a person has committed negligent misrepresentation, if he was negligent in determining whether a statement was true. Additionally, some jurisdictions allow for strict liability in instances where a manufacturer makes a public statement about the safety of a product.

Strict Liability

Although the product's defect is not the fault of the defendant, the defect makes the product unreasonably dangerous, making the defendant responsible under the theory of strict liability.

Section 402A of the Restatement (Second) of Torts included a provision creating strict liability on the part of a manufacturer. Under this section, a manufacturer is liable for product defects that occur during the manufacturing process, despite the level of care used by the manufacturer. Later, courts expanded the strict liability principles to include cases that did not involve manufacturing errors, for instance, cases involving failure of the manufacturer to supply substantial warnings.

Liability for Used Products

A person who re-manufactures a product may in some instances be subject to the same products liability rules as the original manufacturer.

States are split regarding the basis of liability for sellers of used products. Some states exclude sales of used products from products liability rules, but in other states, the general products liability rules apply.