The defendant in a product liability lawsuit may claim that the product did not become defective in their part of the supply chain. For example, the manufacturer could point blame at the retailer, claiming the product acquired a defect because of the way it was stored, or claim the safety warning labeling was the responsibility of another company that packaged and distributed the product. However, in the case of defective prescription or over-the-counter drugs, there is an exception called market share liability. In these cases, the liability for the defect is according to the percentage of sales of the drug in the area where the plaintiff experienced the injury.