Ipse Dixit – It’s Not Just for Analytical Gaps Anymore


There are few legal phrases more fun to say than “ipse dixit.” The phrase is most commonly used in motions to exclude experts who base their opinions on nothing more than their own say so.  As the Court noted in General Electric Co. v. Joiner, 522 U.S. 136 (1997), an ipse dixit – Latin for “he said it himself” – leaves an impermissible “analytical gap” between the expert’s opinion and the facts on which it is based.  But ipse dixit arguments can and should stretch beyond just the “basis” part of the expert argument. Courts should also exclude experts who provide unsupported and self-serving testimony to suggest that their method is accepted generally in the community.

That is precisely what happened in Knepfle v. J-Tech Corporation, 2022 WL 4232598, — F.4th — (11th Cir. 2022).  Plaintiff was injured in a motor vehicle accident when she ran her motorcycle into the side of a vehicle that had turned in front of her, causing her to be thrown from the motorcycle.  Although the helmet she was wearing protected her head during the initial impact with the other vehicle, she alleged that it came off and failed to protect her head when it struck the pavement.  She brought product liability claims against multiple defendants in the manufacturing and distributing chain of the helmet.

In support of her claims, Plaintiff offered an expert who opined (1) that the helmet was not in place during the secondary impact with the pavement, and (2) that the helmet had come off during impact because the helmet’s straps were too short.  The district court excluded both opinions, granted summary judgment on the merits, and denied one defendant’s motion for summary judgment on jurisdictional grounds as moot.

After first concluding that the district court erred in denying the jurisdictional motion for summary judgment, the Eleventh Circuit turned its attention to the expert’s opinions.  The expert based his first opinion – that the helmet had come off between the first and second impacts – on his observation that the helmet’s interior liner was compressed in the front region where the initial impact occurred but was not visibly compressed in the rear, where an impact with the ground would have occurred.  However, although the expert admitted that others in his industry “typically” would use calipers or 3D scanning to inspect a helmet liner – and that he had actually measured the compression on the front of the helmet – he had only “eyeballed” the rear liner to check for compression.

The expert nevertheless testified that “eyeballing” the liner was a generally accepted methodology, and Plaintiff argued that any relevant degree of liner compression would have been visible to the naked eye – i.e., that the lack of visible compression rendered measurement superfluous.  The district court disagreed, refusing to “take [the expert] at his word” regarding the general acceptance of his method, and excluded the opinion.

The Eleventh Circuit affirmed.  The district court was not required “to admit expert opinions based on the ipse dixit of the expert.” In addition, the expert’s inconsistent application of the methodology – measuring the front but not the rear of the liner – seemed “to focus only on obtaining evidence that confirms a predetermined theory.”  Ultimately, the failure to provide “any evidence that other experts accept visual inspections” or prove that the second impact would have resulted in visible liner compression rendered the opinion unreliable.

The expert had also opined that the helmet was defective because its straps were too short and locked together with double D-ring fasteners, which fastened on the left side of the wearer’s chin in a vertical fashion rather than directly underneath the chin.  The expert opined that this vertical orientation would allow the straps to come loose more readily in an accident.  However, his only support for that claim was a demonstration in which he flipped the helmet upside down and manipulated the straps so that they were nearly perpendicular to one another, which he did not prove could possibly happen while a helmet is fastened on the rider’s head.

The Eleventh Circuit affirmed the district court’s exclusion, concluding that the expert had at most proven than that the straps, “free of any friction or resistance that a person’s head would normally provide,” could reach angles at which the system would slip.  Having failed to show that the slippage could occur under real-world conditions, his opinion was unreliable.

It is encouraging whenever a court takes seriously its role as gatekeeper and requires an expert to tie his or her opinions to reality.  Courts have long understood that factual gaps in an expert’s reasoning cannot be remedied by the expert’s ipse dixitKnepfle goes a step farther and shows that a court need not blindly accept an expert’s testimony even on pronouncements of general methodology.  Just as experts may not play fast and loose with the facts of a case, they may not offer self-serving, check-the-box testimony that their methodology is generally accepted and reliable.

The material contained in this communication is informational, general in nature and does not constitute legal advice. The material contained in this communication should not be relied upon or used without consulting a lawyer to consider your specific circumstances. This communication was published on the date specified and may not include any changes in the topics, laws, rules or regulations covered. Receipt of this communication does not establish an attorney-client relationship. In some jurisdictions, this communication may be considered attorney advertising.

About the Author: Eric M. Friedman

Eric Friedman guides clients through all stages of product liability litigation, particularly working with expert witnesses to present the science behind clients' products. By leaning on his pre-law history as a biochemist, he is able to identify key arguments for and against clients and craft winning strategies for both motion practice and trial.

About the Author: Christine R. M. Kain

As a member of Faegre Drinker’s nationally ranked product liability practice, Minneapolis partner Christine Kain defends pharmaceutical, medical device, food and beverage, and other manufacturers in class actions, mass torts, product liability and consumer fraud cases.

©2024 Faegre Drinker Biddle & Reath LLP. All Rights Reserved. Attorney Advertising.
Privacy Policy