Product liability is the body of law that provides for compensation for physical injuries and property damage resulting from defective and unreasonably dangerous products and from the failure of a manufacturer or seller to warn the consumer of product dangers. For example, a manufacturer who sells a pain killer without warning that use of the drug with alcohol could impair the user's ability to operate machinery may be liable if the consumer is injured in this fashion. Defective design is the claim that a product is, at the time it is sold, in a defective condition, unreasonable dangerous to the ordinary consumer. For example, a seller who designs a circular power saw which does not include a blade guard may be liable if the user suffers an injury from the unguarded blade.
Foreseeable misuse includes foreseeable product alterations by the consumer.
A manufacturer must also warn a consumer of dangers associated with product misuse. Sometimes all three theories are pursued in one case. The defect may be in the product's design or manufacturing, in the product's container or packaging, or in the instructions or warning necessary for the product's safe use. In a strict liability case, the injured person is not required to prove the manufacturer or seller was negligent. The duty includes design, manufacture, assembling, instructing and warning.