What exactly does the amended Federal Rule of Evidence 702 say, and when did it take effect?
The amended rule took effect on 1 December 2023, and the Supreme Court’s own order says so. Transmitting the amendments on 24 April 2023, the Court ordered that “[t]he Federal Rules of Evidence are amended to include amendments to Rules 106, 615, and 702,” and that “[t]he foregoing amendments to the Federal Rules of Evidence shall take effect on December 1, 2023, and shall govern in all proceedings thereafter commenced and, insofar as just and practicable, all proceedings then pending.” The date of a filing is therefore not the only thing that matters; the order reaches pending proceedings so far as is just and practicable.
The rule as printed in that order reads: “A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if the proponent demonstrates to the court that it is more likely than not that: (a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue; (b) the testimony is based on sufficient facts or data; (c) the testimony is the product of reliable principles and methods; and (d) the expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.”
Two edits produced that text. The opening clause gained the words “if the proponent demonstrates to the court that it is more likely than not that,” and subdivision (d) was rewritten from the previous requirement that “the expert has reliably applied the principles and methods to the facts of the case.” The blackline the Advisory Committee sent forward shows precisely that substitution. The published pamphlet of the Federal Rules of Evidence records the amendment history for Rule 702 as “Apr. 17, 2000, eff. Dec. 1, 2000; Apr. 26, 2011, eff. Dec. 1, 2011; Apr. 24, 2023, eff. Dec. 1, 2023.”
What did the 2023 amendment change about the proponent’s burden?
It put an existing burden into the text of the rule because courts were not applying it. The Advisory Committee’s note to the 2023 amendment states that “the rule has been amended to clarify and emphasize that expert testimony may not be admitted unless the proponent demonstrates to the court that it is more likely than not that the proffered testimony meets the admissibility requirements set forth in the rule,” and identifies the standard as the familiar one: “This is the preponderance of the evidence standard that applies to most of the admissibility requirements set forth in the evidence rules,” citing Bourjaily v. United States, 483 U.S. 171, 175 (1987), and Huddleston v. United States, 485 U.S. 681, 687 (1988).
The note then names what it is correcting, in a sentence worth reading in full: “But many courts have held that the critical questions of the sufficiency of an expert’s basis, and the application of the expert’s methodology, are questions of weight and not admissibility. These rulings are an incorrect application of Rules 702 and 104(a).” In its report to the Standing Committee dated 15 May 2022, the Advisory Committee on Evidence Rules described the same problem in its own words, concluding that in “a fair number of cases, the courts have found expert testimony admissible even though the proponent has not satisfied the Rule 702(b) and (d) requirements by a preponderance of the evidence.” It also recorded why the published language changed: more than 500 comments were received, “almost all of the fire was directed toward the term ‘preponderance of the evidence,’” and the text was altered to say “more likely than not.”
The note is equally careful about what did not change. Some challenges still go to weight: “if the court finds it more likely than not that an expert has a sufficient basis to support an opinion, the fact that the expert has not read every single study that exists will raise a question of weight and not admissibility.” Competing experts are not automatically a reason to exclude either of them — “by deciding the disputed facts, the jury can decide which side’s experts to credit” — and the reliability threshold remains below a correctness threshold, because “[t]he evidentiary requirement of reliability is lower than the merits standard of correctness.” The note also states that the amendment does not require the court to make “a finding of reliability in the absence of objection.” Whether any of this changes the result in a given matter is for the trial judge, and this Institute does not predict that.
What did the amendment change about an expert overstating the conclusion?
Subdivision (d) was redirected from the expert’s application of the method to the opinion that came out of it. The Advisory Committee’s note states: “Rule 702(d) has also been amended to emphasize that each expert opinion must stay within the bounds of what can be concluded from a reliable application of the expert’s basis and methodology.” Its reason is about juries: they “may also lack the specialized knowledge to determine whether the conclusions of an expert go beyond what the expert’s basis and methodology may reliably support.”
The Committee considered a stronger version and rejected it. Its 15 May 2022 report records that a proposed new subdivision (e) “that would essentially prohibit any expert from drawing a conclusion overstating what could actually be concluded from a reliable application of a reliable methodology” was set aside, because “Rule 702(d) already requires that the expert must reliably apply a reliable methodology,” and because of concern about “the possible unintended consequences of adding an overstatement provision that would be applied to all experts, not just forensic experts.” The report links the change to a 1997 decision: the amendment “is consistent with General Electric Co., v. Joiner, 522 U.S. 136 (1997), in which the Court declared that a trial court must consider not only the expert’s methodology but also the expert’s conclusion.”
The note limits the change in three ways that matter to civil practice. The overstatement concern is “especially pertinent to the testimony of forensic experts in both criminal and civil cases,” which is emphasis rather than exclusivity. “Nothing in the amendment imposes any new, specific procedures.” And “nothing in the amendment requires the court to nitpick an expert’s opinion in order to reach a perfect expression of what the basis and methodology can support. The Rule 104(a) standard does not require perfection. On the other hand, it does not permit the expert to make claims that are unsupported by the expert’s basis and methodology.” The Institute’s general material on admissibility practice is at Daubert & expert admissibility.
How have courts applied the amended rule since December 2023?
Federal courts of appeals have acknowledged the amendment and then decided the cases on grounds that predate it. In In re Onglyza (Saxagliptin) and Kombiglyze (Saxagliptin and Metformin) Products Liability Litigation, 93 F.4th 339, No. 22-6078 (6th Cir. 13 February 2024), Judge Nalbandian wrote that “[o]n December 1, 2023, two changes to Rule 702 went into effect. First, language was added to clarify that the proponent bears the burden of showing the expert testimony more likely than not complies with the rule.” The court affirmed the exclusion of a general causation expert whose Bradford Hill analysis had, on that record, “cherry-picked data to bolster his case,” and, quoting In re Lipitor (Atorvastatin Calcium) Marketing, Sales Practices & Products Liability Litigation, 174 F. Supp. 3d 911, 932 (D.S.C. 2016), that a failure “to adequately account for contrary evidence is not reliable or scientifically sound.”
The largest environmental application so far was a district court one. In In re Paraquat Products Liability Litigation, No. 3:21-md-3004-NJR (S.D. Ill. 17 April 2024), Chief Judge Rosenstengel excluded the plaintiffs’ sole general causation expert and, the same day, dismissed the four trial selection cases, writing that “Dr. Wells’ exclusion mandates the dismissal of the four trial selection cases” and that with the exclusion “the trial selection cases necessarily fail on an essential element of each of their claims.” The MDL involved “over 5,000 individual Plaintiffs” alleging Parkinson’s disease from paraquat dichloride exposure. Plaintiffs’ counsel had conceded at the evidentiary hearing that without that expert “the odds ratio over two, which we utilize for specific causation … would be dispositive of these cases.”
Two more recent Eleventh Circuit decisions show the framework operating without leaning on the amendment at all. In In re Deepwater Horizon BELO Cases (11th Cir. 18 October 2024) the court affirmed exclusion of two general causation experts and the judgment for BP, and in The Estate of Carol Davis v. Lockheed Martin Corp., Nos. 24-10080 and 24-10416 (11th Cir. 28 July 2026), it affirmed exclusion of two experts and summary judgment in a volatile organic compound case. The Federal Judicial Center’s advice on this mixed picture is explicit: “pre-amendment cases may remain instructive in applying Rule 702, as amended,” but “[j]udges and litigants should exercise caution in relying on pre-amendment cases, however, because the 2023 amendment was designed to correct misapplications of the rule in some federal cases.” State courts are a separate question, and many apply their own standard; New York, for example, applies the general acceptance test of Frye, as the Court of Appeals did in Parker v. Mobil Oil Corp., 7 N.Y.3d 434 (N.Y. 2006).
What are the recurring grounds for excluding a toxic tort expert?
Four grounds recur in the decisions collected on this page, and the first is extrapolation across dose. An opinion built on studies at occupational concentrations does not automatically reach an environmental exposure, and the gap has to be argued rather than assumed. The Eleventh Circuit’s formulation, repeated in In re Deepwater Horizon BELO Cases (18 October 2024), is that a toxic-tort plaintiff “must demonstrate the levels of exposure” to the alleged toxin “that are hazardous to human beings generally,” quoting McClain v. Metabolife International, Inc., 401 F.3d 1233, 1241 (11th Cir. 2005); in 2026 the same court repeated in The Estate of Carol Davis v. Lockheed Martin Corp. that “[a] plaintiff must demonstrate the level of exposure to the allegedly harmful chemical that is hazardous to a human being.” Circuits and states differ in how strictly they apply this, so the forum has to be named before the rule is stated.
The second is borrowing a study population that does not match the claimant. The Reference Manual on Scientific Evidence, Fourth Edition, states the condition directly: “Only if the study participants and the plaintiff are similar with respect to relevant risk factors will a risk estimate from a study or studies be valid when applied to an individual.” Its illustration is a lung cancer study of subjects who “have smoked half a pack of cigarettes a day for 20 years,” whose increased incidence “cannot be extrapolated to someone who smoked two packs of cigarettes for 30 years, without strong assumptions about the dose–response relationship.” Texas built the same requirement into its sufficiency rule in Merrell Dow Pharmaceuticals, Inc. v. Havner, 953 S.W.2d 706 (Tex. 1997): “A claimant must show that he or she is similar to those in the studies.”
The third is background risk. Amended Rule 702 places the showing on the proponent, who must demonstrate to the court that it is “more likely than not” that the rule’s requirements are met, so a disease with a substantial rate of occurrence in the unexposed population is part of what the proponent’s own analysis has to absorb rather than an objection for the opponent to raise. The Reference Manual explains the arithmetic behind the attributable risk on which these arguments run — it is “that portion of the excess risk that can be attributed to an agent, above and beyond the background risk that is due to other causes” — and warns that the whole inference depends on “group studies identifying a genuine causal relationship and a reasonably reliable measure of the increased risk,” which requires attention to random error, bias and confounding. Tamraz v. Lincoln Electric Co., 620 F.3d 665 (6th Cir. 2010), is the illustration on the individual side: the expert’s “efforts to ‘rule in’ manganese exposure as a possible cause or to ‘rule out’ other possible causes turned on speculation, not a valid methodology.”
The fourth is the oldest and the one the amendment speaks to most directly. In General Electric Co. v. Joiner, 522 U.S. 136 (1997), the Supreme Court held that “conclusions and methodology are not entirely distinct from one another,” that “nothing in either Daubert or the Federal Rules of Evidence requires a district court to admit opinion evidence which is connected to existing data only by the ipse dixit of the expert,” and that a court “may conclude that there is simply too great an analytical gap between the data and the opinion proffered.” Amended Rule 702(d) now asks the same question in the rule’s own words. Whether a particular opinion clears it is for the trial judge, reviewed for abuse of discretion; nothing here is legal advice, and nothing here states that any substance caused or did not cause any person’s illness. Preserving the physical record that these opinions are built on is a separate and time-limited problem, covered at Evidence preservation, and data usability at Sampling, QA/QC & data usability.