Lee Mickus is a partner in the Denver, CO office of Evans Fears Schuttert McNulty Mickus LLP.

Editor’s Note: In a relatively short amount of time, Lee Mickus has become one of the most prolific contributors to WLF’s Legal Studies Division in its 37-year history. The focus of his numerous papers is Rule 702 of the Federal Rules of Evidence and, more specifically, the rule’s amendment.  He also a member of Lawyers for Civil Justice, for which he’s done yeoman’s work as Co-Chair of its Rule 702 Committee. He prepared the list of 14 cases as part of his work on that committee, and we are privileged to share them with our readers.

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  1. Cohen v. Cohen, 2025 WL 45704 (3d Cir. Jan. 8, 2025).  The court overturned the admission of an expert because the district court undertook “no engagement with the arguments raised” in a Rule 702 motion challenging the reliability and fit of the expert’s opinions. “A district court’s gatekeeping responsibilities are not negated by the existence of an opposing expert, nor can a district court delegate its duty to the parties.”
  2. In re Deepwater Horizon BELO Cases, 2024 WL 4522690 (11th Cir. Oct. 18, 2024).  The court affirmed exclusion of the plaintiffs’ general causation experts, finding that their failure to identify a threshold exposure dose that will produce harm rendered their methodology unreliable.
  3. In re Chrysler Pacifica Fire Recall Prods. Liab. Litig., 2025 WL 520570 (E.D. Mich. Feb. 18, 2025).  The 2023 amendment to Rule 702 was enacted “to reinforce the idea, sidestepped sometimes by some courts, that Evidence Rule 104(a) entrusts the court with deciding whether the admissibility criteria have been satisfied, rather than treating them as ‘questions of weigh’” to be determined by the factfinder.”  An essential admissibility criterion is Rule 702(b), which requires that the opinion have sufficient factual foundation. But this is necessarily lacking where “the factual premise for [the expert’s] conclusion is indisputably wrong” and so the opinion must be excluded.
  4. Sims v. BMW of N. Amer. LLC, 2025 WL 484228 (M.D. Fla. Feb. 13, 2025).  A reliable accident reconstruction methodology must reconcile the physical evidence with the expert’s hypothesized vehicle movements, and the reconstruction becomes suspect when the expert “fails to consider or account for contradictory data.”  The court excludes certain opinions in this case because the expert “commits the sin of omitting data—the gouge mark, fluid spill, the Trooper’s testimony, and cherry-picking data—giving undue weight to [one party’s] version of the events.”
  5. Crystal Lagoons U.S. Corp. v. Cloward H2O LLC, 2025 WL 384995 (D. Utah Feb. 4, 2025).  The court recognizes that the 2023 amendment rejects the idea that Rule 702 prefers admission of expert testimony over exclusion.  Instead, the “[r]ecent amendments to Rule 702 were meant to clarify that there is no presumption of admissibility with respect to expert testimony. Instead, to be admissible, the proponent of the expert evidence bears the burden to demonstrate it is more likely than not that Rule 702’s requirements are satisfied.”  The court excluded a number of the expert’s opinions because the plaintiff failed to carry that burden of proof and did not demonstrate that a sufficient factual foundation supported the analysis.
  6. Klein v. Meta Platforms, Inc., 2025 WL 295361 (N.D. Cal. Jan. 24, 2025).  The court described the 2023 amendments as “intended to amplify” the requirements of Rule 702. Courts must evaluate whether an expert identified sufficient facts or data to support every necessary link in her theory, and where that support is lacking may exclude the opinions due to the existence of an “analytical gap.”  The court excluded the opinions at issue because the expert lacked a factual basis for a step necessary to reach his conclusion.
  7. Huss v. Sharkninja Operating LLC, 2025 WL 257226 (S.D. Ind. Jan. 21, 2025).  The 2023 amendment mandates that the proponent show by a preponderance of proof that the Rule 702 elements have been established and also “requir[es] the Court to determine whether an expert’s methodology is reliable rather than leaving that determination to the jury.”  The court excluded the expert because the plaintiff “has not sustained her burden of showing by a preponderance of the evidence that [the expert’s] methodology is reliable.”
  8. U.S. v. Jefferson, 2025 WL 97378 (W.D. Wash. Jan. 12, 2025).  Under amended Rule 702, “the proponent of the expert testimony bears the burden of proving by a preponderance of the evidence that the testimony being proffered is admissible.” It is the responsibility of the court to determine that the expert’s opinions are reliable, rather than deferring that determination to the jury, even when the opinions arise from the expert’s experience.  The court excluded most of the experience-based expert’s opinions because the defendant “has not shown that it is more likely than not that the testimony of [the] defense expert meets the requirements of Rule 702 of the Federal Rules of Evidence.”
  9. Justice v. Beltway (USA), Inc., 2024 WL 5245595 (E.D. Mo. Dec. 30, 2024).  The 2023 amendment requires the proponent to establish that an expert’s opinions are admissible by a preponderance of the evidence and clarifies that the sufficiency of an expert’s factual basis and the reliability of the expert’s application of her methodology to the facts of the case are admissibility issues for the court to decide.  The court found inadmissible a key opinion because “Plaintiffs have failed to establish by the preponderance of the evidence” that the opinion “is based on sufficient facts and data and is the result of a reliable application of a methodology.”
  10. Kopp Development, Inc. v. Metrasens, Inc., 2024 WL 4826381 (N.D. Ohio Nov. 19, 2024).  The 2023 amendment confirms that the expert’s proponent bears the burden of establishing admissibility, and that the expert’s factual foundation must be shown sufficient in order for the opinion testimony to be admitted.  The proffered expert in this case, however, unreliably based his opinion exclusively on projected data received from the plaintiff without performing any evaluation of those projections.
  11. In re Terrorist Attacks on September 11, 2001, 2024 WL 5077293 (S.D.N.Y. Dec. 11, 2024).  The court observed that the Advisory Committee on Evidence Rules “proposed the changes [reflected in the 2023 amendment] in response to court decisions that admitted expert testimony too liberally,” and the enactment of the amendment “reflect[s] an intent to empower courts to take seriously their roles as gatekeepers of expert evidence.”  The court excluded opinions from an expert who purported to apply his experience but the conclusions he reached did not have factual support and failed “to account for . . . reasonable alternative explanations,” leaving an unacceptable analytical gap between his basis and his opinions.
  12. Brashevitzky v. Reworld Holding Corp., 2024 WL 4784144 (S.D. Fla. Nov. 13, 2024).  Under amended Rule 702, “the burden is on the party offering the expert testifying based on experience to explain how that experience led to the conclusion he reached, why that experience was a sufficient basis for the opinion, and just how that experience was reliably applied to the facts of the case.”  The court excluded the expert’s opinions where the witness did not explain how his experience allowed him to identify specific areas that were contaminated: “there is too great of an analytical gap between [the expert’s] incomplete analysis in his declaration and his opinion to be admissible[.]”
  13. Jensen v. Camco Mfg., LLC, 2024 WL 4566781 (D. Ariz. Oct. 24, 2024). Judge David Campbell, the former Chairman of the Judicial Conference Committee on Rules of Practice and Procedure, observed that the 2023 amendment clarified that court’s gatekeeping responsibility: “if the proponent does not meet its Rule 702 burden, the expert testimony is not admissible.”  In considering engineering opinions based on a “differential diagnosis” methodology applied to determine if a product defect caused an accident, the court observed that this type of analysis “is reliable only if the expert first ‘ruled in’ only those potential causes that could have produced the injury in question.”  The court ruled that the opinions must be excluded:  “He speculates that the flame must have been due to some transient defect he did not detect, but speculation is not a reliable engineering method under Rule 702(c).  And relying on a speculative cause because it ‘cannot be ruled out’ is not a reliable application of an engineering method to the facts of this case under Rule 702(d).”
  14. Colwell v. Sig Sauer, Inc., 2024 WL 4216047 (N.D.N.Y. Sept. 17, 2024).  The court was troubled where the expert expressed an opinion on causation “without reference to the specific facts” underlying the plaintiff’s incident—“there was no video footage, no explanation as to why Colwell’s pistol discharged, and no experimentation.”  In light of this lack of foundation, the court concluded that the “causation opinion does not pass muster under Fed. R. Evid. 702 because it is not ‘based on sufficient facts or data’; it is not ‘the product of reliable principles and methods’ and it does not ‘reflect[ ] a reliable application of the principles and methods to the facts of the case.’”