Michael A. Salvati

Product liability suits often involve complex machinery or detailed questions of product design and engineering. Thus, when defendants seek to preclude a plaintiff’s experts from testifying, they often try to kill two birds with one stone. Without experts to explain nuanced questions of defect and causation, the defense will argue that the plaintiff’s claims must fail as a matter of law. In a recent decision, the Third Circuit reversed a trial court that had reached such a conclusion. 

In Slatowski, the plaintiff shot himself in the leg and blamed his firearm for being too easy to fire. Although the plaintiff had two experts to explain the firearm’s internal workings and the specifics of several recommended alternative designs, the trial court excluded those experts’ causation opinions as speculative. Just because the plaintiff’s pistol could have been accidentally fired, there was no reliable evidence that it did so on this particular occasion. Without an expert to discuss the issue of causation, the District Court granted summary judgment for the defendant.

The Third Circuit reversed, explaining that expert testimony is only needed when, considering all the admissible evidence, the jury cannot reach a decision without speculating. 

As examples, the court noted that where a theory of harm is technical or abstract, expert opinion might be required—as when a mold infestation may be caused by a leaky toilet or by a fungus. Alternatively, in a product liability case, if something has gone very wrong with a product but the plaintiff is not sure what—as when a van suddenly catches fire—an expert may be needed to explain why. But even when the subject matter of a case is complex, the Third Circuit concluded that an expert is not needed when “lay testimony can tell the story of causation.” 

The fact that the plaintiff had expert testimony on the issue of defect—how the pistol functioned internally and how alternative designs would have changed things—made the question of causation relatively simple. Given the anticipated testimony regarding how the pistol’s trigger worked, did the jury believe the plaintiff’s testimony that some debris could have gotten in his holster and activated the trigger? That, the Third Circuit held, was a simple enough question for a jury to decide without expert assistance.

Defense practitioners who challenge a plaintiff’s experts should be aware of this decision and bolster the summary judgment portion of their motions accordingly.
 

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_{Case Law Alerts, 4th Quarter, October 2025 is prepared by Marshall Dennehey to provide information on recent developments of interest to our readers. This publication is not intended to provide legal advice for a specific situation or to create an attorney-client relationship. Copyright © 2025 Marshall Dennehey, all rights reserved. This article may not be reprinted without the express written permission of our firm.}