The crucial importance of laying an adequate foundation for expert opinion testimony.

Rule 702 of the Minnesota Rules Evidence provides that “[an expert’s] opinion must have foundational reliability.”  This is the functional equivalent of Fed. R. Evid. 702’s requirement that testimony be “based on sufficient facts or data.”  Other states undoubtedly impose the same requirement.  Indeed, long before the promulgation of formal rules and codes of evidence, the common law barred expert testimony that lacked a proper foundation.  I vividly remember the first case I briefed to the Rhode Island Supreme Court back in 1979, which dealt with precisely this issue: the trial judge had excluded our expert’s causation testimony on the ground that my colleague who tried the case had not established an adequate foundation.  (I was the new guy in the office, and as a typical law review geek fresh off a judicial clerkship, legal research and writing was my only strong suit.)  My appellate brief was based entirely on case law, as Rhode Island did not adopt formal rules of evidence until 1987.  Suffice to say, neither my brief nor my colleague’s oral argument persuaded the court that the trial judge had abused his discretion

In Kedrowski v. Lycoming Engines, (9/11/2019), the Minnesota Supreme Court did a deep dive on this issue.  The case is noteworthy because of the court’s painstaking (and therefore necessarily lengthy) analysis of the multiple grounds for the expert’s testimony on causation, as a result of which the court was able to distinguish between testimony that the trial judge properly excluded and testimony that he should have admitted.

The first paragraph of the opinion summarizes the case as concisely as possible:

This litigation arises from the crash of a single-engine airplane, which resulted in serious injuries to appellant Mark Kedrowski, the pilot of the airplane. According to Kedrowski’s expert, a defective fuel pump manufactured by respondent Lycoming Engines caused the airplane to lose power and crash. After the jury returned a $27.7 million verdict for Kedrowski, the district court ruled that the opinion of Kedrowski’s sole expert on causation lacked foundational reliability under Minn. R. Evid. 702 and that the expert’s opinion should have been excluded in its entirety. Following the posttrial evidentiary ruling, the district court granted judgment as a matter of law to Lycoming, and the court of appeals affirmed.  We hold that the district court’s evidentiary exclusion was overbroad and an abuse of discretion and that a new trial on liability is required.

The plaintiff engaged a well-qualified aircraft accident reconstruction expert, Donald Sommer.  His opinion that manufacturing defects in the fuel pump caused the plane to lose power and crash was based, as the court says, on “a multifaceted investigation,” which included the following:

  1. The airplane’s propeller was not severely damaged by the crash – to the contrary, the expert testified that “the propeller was ‘virtually pristine….[Y]ou will never find a blade like this on an engine that’s making power.’ Sommer testified that the propeller analysis showed that the engine was producing ‘low power at impact.’”
  2. Sommer installed the engine (which was largely undamaged) on a dynamometer, which showed that the engine was producing 40 percent less horsepower than it should have – in other words, “the engine was ‘not running right.’”
  3. The plaintiff told Sommer of  “occasions where he would engage a separate boost pump when starting the plane, ‘which is normal.’ But when Kedrowski would turn off the boost pump, the engine would die….Sommer testified that…‘if an engine will run only with the boost pump on and stops running when the boost pump is off…that’s pretty much…a no brainer to me that the engine-driven pump was not providing for the needs of the engine.’”
  4. A specified volume of fuel per hour should flow through a pump at a given pressure output – and conversely, the pump should produce a specified pressure output at a given flow rate.  Sommer tested the pump on a diagnostic tool called a flow bench and opined, based on the test results, that “the pump ‘was not capable of producing design flow and pressure and…was substandard.’”
  5. Sommer disassembled the pump, tested the valves for air leaks, and found “a very serious set of leaks in both the inlet and outlet check valves.”  He also found that one of the valves had not been installed properly.
  6. Sommer also disassembled the engine to see if he could find another possible cause of the of the power loss – but he couldn’t.  “‘[E]very component that could possibly have caused this engine to fail was analyzed, and there was only one that was found with defects, and that’s the engine-driven pump.’” 
  7. Finally, Sommer installed the pump on another airplane and found that “‘the engine wouldn’t start without an excessive amount of cranking.  So something was wrong, and the only difference was the pump.’”

The court affirmed the trial judge’s conclusion that Sommer’s flow-bench testing methodology (item 4 above) lacked foundational reliability, because “Sommer could not consistently explain why he ran the flow-bench test as he did.”  He initially “explained his opinion about the pump, derived from the flow-bench testing, specifically in terms of design parameters….But when confronted with the parameters from Lycoming’s design drawings” – which were not the parameters he used for the flow-bench test – “Sommer changed course.  [He] was no longer concerned with the pump’s design, but rather with the pump’s effect on engine performance.”  And to top it off, “[n]either of Sommer’s explanations correspond to the parameters that Sommer actually employed in the testing process.”  In short, “An expert should be able to explain test methodology consistently.  If the expert cannot do so, the district court does not abuse its discretion by excluding evidence of that testing under Rule 702.”

But “the district court’s leap from this sound result to the conclusion that Sommer’s entire causation opinion should be stricken is puzzling….Where a portion of the proffered expert testimony is reliable, wholesale exclusion can constitute an abuse of discretion. [T]he district court excluded Sommer’s entire causation opinion because it was ‘apparent’ that the ‘scientific underpinnings’ of Sommer’s opinion depended entirely on the validity of the flow-bench testing.  But Sommer based his causation opinion on more than the flow-bench testing” – i.e., his opinion was also based on items 1 – 3 and 5 – 7 above.  The court summarized some (but not all, for some reason) of the other factual bases for the expert’s opinion.  It also considered and rejected the trial court’s two additional rationales for excluding all of Sommer’s testimony, which I will not go into here, and concluded as follows:

In sum, we conclude that the flaws in Sommer’s flow-bench testing are not sufficient to exclude Sommer’s ultimate opinion on causation. From Sommer’s testimony as a whole, even without referencing the flow-bench testing, the jury could draw the inference that the loss of aircraft power was the result of the (undisputed) manufacturing defects present in the Lycoming pump and a substantial factor in the airplane crash and Kedrowski’s resulting injuries. Moreover, the flaws that the district court found in the factual foundation of Sommer’s opinion were questions of weight and credibility for the jury to resolve. We therefore hold that the wholesale exclusion of Sommer’s causation opinion was an abuse of discretion…. We therefore also reverse the judgment as a matter of law in favor of Lycoming…. Because the flow-bench testing relates only to the liability of Lycoming, and liability is “distinct and separable” from the issue of damages, we grant a new trial only on the issue of liability.

What are the takeaways from all this?  First, if the circumstances of a case are such that the expert can provide more than one basis for his or her opinion, that absolutely should be done.  Second, trial lawyers should cross-examine their experts as vigorously as they expect opposing counsel to – more vigorously, if possible – not only to prepare the expert to stand up under withering cross-examination by opposing counsel, but also in the hope of exposing a foundational flaw, like the one that the trial court found and the supreme court affirmed in Kedrowski v. Lycoming.  Of course, given the complex technical nature of the flow-bench testing and the expert’s undoubtedly firm conviction of his methodology’s validity, it might have been impossible for plaintiff’s counsel to suss out the flaw in that methodology – but it’s always worth a shot.  If the plaintiff’s attorney in Kedrowski had discovered the weakness of the flow-bench testing and had told the expert not to testify about it at trial, the plaintiff would have been spared the time and expense of an appeal.  (Two appeals, actually, as Minnesota has an intermediate appellate court, which in this case affirmed the trial judge’s ruling.)  And finally, whether the expert’s opinion is based on one foundational factor or many, counsel should rigorously review, clearly understand, and (if warranted) challenge the foundation.  The expert will either refute the challenge or use it to strengthen the foundation, either of which is a good outcome. 

One final comment: Vident Partners is not merely an expert referral service – we are, in fact, a consulting firm that specializes in expert search and referral.  The comprehensive, in-depth conversations that we have with our clients and with potential experts frequently enable us to provide the client with new insights into a case, to sharpen the issues, or to determine that the case requires an expert in a different field of specialization than the one the client originally requested.  This is what makes us consultants, not simply an expert referral service, and it’s a value-added aspect of working with us at no extra charge.  You may never need us to provide anything more than expert referral – but if you do, we are willing and able to expand our services to meet your needs.  In particular, in light of the foregoing discussion, should you ever need us to research the foundation of an expert’s opinion or help prepare an expert for cross-examination, we would be happy to quote a fee for such services.

Stay safe.  Best wishes for health and courage to all of our clients and experts, especially to the doctors, nurses, physician assistants, EMTs, etc. who are on the front lines.



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