A plaintiff who alleges that a product is defective usually has to offer expert testimony in support of that allegation.  This should come as no surprise for complex products – if it took a team of scientists and engineers to bring the product to market, then a lay jury should not be asked to evaluate an alleged defect in that product without the aid of expert testimony.  But what if a plaintiff alleges a defect in the design of a relatively simple, more familiar component of a complex product?  The Third Circuit recently addressed that question in an opinion that, although nonprecedential and in some respects peculiar to New Jersey law, illustrates how a court should approach the issue.

In Kuhar v. Petzl Co., 2022 WL 1101580 (3d Cir. Apr. 13, 2022), Plaintiff fell and injured himself while using a safety harness that he had purchased as part of a kit seven years earlier.  He alleged that the fall occurred because a bolt attached to the carabiner of the safety harness had snapped due to a design and/or “indeterminate” or manufacturing defect.  In support of his claims, Plaintiff proffered a metallurgical and materials sciences expert who identified two alleged design defects – a “sharp profile change” and “sharp threads on the bolt” – and machining grooves that the expert deemed a manufacturing defect, some combination of which he claimed had caused the accident.  But some of the expert’s defect and causation opinions were “net opinions” – New Jersey parlance for “ipse dixit” opinions – and were excluded for lack of supporting data.  Other opinions were excluded because the expert failed to define his terms or explain his reasoning.  The Third Circuit agreed with the district court that the expert’s opinions lacked both reliability and fit, and affirmed its exclusion of all of the expert’s opinions.

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