Causation in personal injury actions, including product liability claims related to drugs and medical devices and toxic tort actions related to exposure to hazardous substances, must be proven within a reasonable degree of medical probability based upon competent expert testimony. That’s typically the plaintiff’s burden of proof. Do the defendants bear the same burden? In Kline v Zimmer, the California Court of Appeal recently held that, in challenging the plaintiff’s causation evidence, defense expert testimony should be held to a standard of “less than a reasonable medical probability.”
Kline involved the plaintiff’s claim that the Durom Cup hip implant, manufactured by defendant Zimmer, Inc. and utilized in his first hip replacement surgery, was defective and caused him to require an additional surgery, which resulted in further injury. Evidence presented by the plaintiff at trial included an expert who testified to a reasonable medical probability that the Durom Cup’s defects caused the plaintiff to need the additional surgery, which resulted in changes in his muscles and soft tissues causing him chronic pain.