Like negligence, the strict product liability theory requires the plaintiff to prove four elements: (1) a strict duty to supply a safe product; (2) a breach of that duty; (3) causation; and, (4) damages. However, strict liability differs from negligence in two key ways. First, under a strict liability theory, the existence of a duty is shown when there is a commercial supplier that manufactures or retails the product – not just a casual seller. Second, under a strict liability theory, the plaintiff does not need to show that the breach of duty is the result of any negligent action. The mere fact that the product was dangerous or defective is enough to establish a breach of the supplier’s duty. The element of causation can often be the most difficult to prove. Usually, scientific reports and studies are presented by the defense to dispute that asbestos did not cause the injury alleged. Further, as there is a substantial amount of time between exposure to asbestos and the appearance of an injury, the defendants may use that passage of time to argue the injury was caused by exposure to another toxic substance, or a product manufactured by someone else. Therefore, in order to prove causation, the plaintiff must show that the asbestos-containing product can cause the injury claimed, that the plaintiff was exposed to the asbestos in a quantity large enough to cause the injury claimed, and that the plaintiff was not exposed to some other toxic substance or product that could have caused the injury.