California law recognizes that a plaintiff must prove that if the defendant did not act in the way complained of, the plaintiff's injuries would not have occurred. In this case, the plaintiff alleged that if the doctors accused of failing to diagnose his colon cancer had conducted proper testing, he would not have died. This is known as "but for" causation. The doctors argued that even if they had properly diagnosed the cancer, the patient would have died anyway.
At issue are the instructions given to the jury. The court refused to instruct the jury about "but for" causation, but instead gave an instruction that allowed a finding of liability if the defendants' actions were a "substantial factor" in causing the injury. An amicus letter from the NAM and other business groups supported the defendants by arguing that this instruction was ambiguous and insufficient to clearly and precisely communicate the legal standard to be used. The issue is important because manufacturers are often involved in product liability litigation in which such an instruction is critical.
In early August, the California Supreme Court declined to hear this appeal.