For product liability practitioners, issues regarding liability historically have been won or lost in a battle of the experts. The reason: The plaintiff must show the product at issue contains a defect, which existed at the time it left the manufacturer’s control, that caused the plaintiff’s injury. Whether on the side of the plaintiff or the defendant, the most significant liability battle is waged over proving the existence of a defect, which usually requires reliance on expert testimony. With the increasing reliance of plaintiffs’ counsel on the malfunction theory to establish product defect, the focus in some product liability cases has shifted from reliance on effective expert testimony to reliance on creative and effective lawyering.
Decades ago, American jurisprudence began blurring the lines between classic strict liability and negligence principles in product liability lawsuits. The lines initially were blurred with the application of res ipsa loquitur principles to liability issues and with the application of comparative fault principles to damage issues. In many jurisdictions today, those lines are not merely blurred but have overlapped. Focusing on liability issues, this overlap has occurred with the increasingly widespread acceptance of circumstantial evidence – in certain cases – to establish the existence of a defect. This doctrine has been called the “malfunction theory,” the “indeterminate defect theory” or simply has been referred to as the application of res ipsa loquitur or circumstantial evidence principles to product liability cases. Perhaps the most potent harbinger that the malfunction theory is here to stay is its 1998 incorporation into the Products Liability Restatement �3.
