What standards apply in proving that a product was defective?

This depends on the theory of liability that an injured party is pursuing. If one is bringing an action under negligence, he must show that the defect that caused the injury came about through the defendant's failure to exercise reasonable care in the design, manufacture, and marketing of the product. In a strict liability case, the general test is whether the product itself was unreasonably dangerous, regardless of the care used in designing or producing it. Finally, in a breach of warranty case, the focus is on whether product was fit for use under it's express or implied warranty.