What does the amended Federal Rule of Evidence 702 actually say, and when did it take effect?
The amended rule took effect on December 1, 2023, and it reads in full: “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.” The official text carries its amendment history beneath it: “As amended Apr. 17, 2000, eff. Dec. 1, 2000; Apr. 26, 2011, eff. Dec. 1, 2011; Apr. 24, 2023, eff. Dec. 1, 2023.”
The effective date decides which text governs a matter already underway. The Supreme Court’s order of April 24, 2023 provides that the amendments “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.” That is why appellate opinions issued well after the amendment sometimes apply the 2011 version: the trial under review happened first. The First Circuit did exactly that in D’Pergo Custom Guitars, Inc. v. Sweetwater Sound, Inc., decided July 30, 2024, setting out the 2011 text and noting in a footnote that “[i]n December 2023, two years after the trial, Rule 702 was amended” and that it would “apply the version of Rule 702 in effect at the time of the bench trial.” By contrast, the Federal Circuit in EcoFactor, Inc. v. Google LLC, 137 F.4th 1333 (Fed. Cir. 2025) (en banc), decided May 21, 2025, set out the amended text, introducing it as “Rule 702 as amended in 2023.” The list of four requirements did not change; the prefatory clause and subsection (d) did, the latter moving from “the expert has reliably applied the principles and methods to the facts of the case” to “the expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.”
What did the 2023 amendment change about the proponent’s burden?
It put in the rule’s own text what had been contested in practice: the party offering the damages expert must satisfy the court that each requirement is more likely than not met, and a shortfall in the factual basis is an admissibility question rather than something for the jury to weigh. The advisory committee’s note to the 2023 amendment says of rulings treating the reliability requirements as going to weight that “[t]hese rulings are an incorrect application of Rules 702 and 104(a).”
Courts applying it have been careful to say the change clarified rather than raised the bar. In EcoFactor the Federal Circuit wrote that “[i]n 2023, Rule 702 was amended to clarify that the proponent of expert testimony bears the burden of establishing its admissibility and to emphasize that an expert’s opinion must stay within the bounds of a reliable application of the expert’s basis and methodology,” adding in a footnote that “[t]he 2023 amendment did not substantively change the relevant standard.” The First Circuit said much the same in D’Pergo Custom Guitars, Inc. v. Sweetwater Sound, Inc., decided July 30, 2024, applying the 2011 version because the bench trial predated the amendment and noting that “the 2023 amendments do not meaningfully affect our analysis.”
Can a damages opinion be excluded because the expert overstated what the method supports?
Yes, and that is the concern subsection (d) was rewritten to reach. The advisory committee’s note to the 2023 amendment explains why the court rather than the jury has to police it, in language the First Circuit drew on in ZipBy USA LLC v. Parzych, Nos. 24-1494, 24-1500, 24-1586 (1st Cir. Mar. 19, 2026). The note reads that judicial gatekeeping “is essential because just as jurors may be unable, due to lack of specialized knowledge, to evaluate meaningfully the reliability of scientific and other methods underlying expert opinion, jurors 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.” A jury can hear that two experts disagree. It is in a worse position to see that one of them has run a recognized method past the point where its inputs support it.
Damages work reaches past its data in recognizable ways: a before period extended into a forecast horizon no record supports, a handful of transactions treated as representative of a population nobody defined, a growth rate observed over a short interval projected across a long one. None of those is a mathematical error and all are visible in the report. In General Electric Co. v. Joiner, 522 U.S. 136, 146 (1997), quoted in EcoFactor, the Supreme Court said that “[n]othing in either Daubert or the Federal Rules of Evidence requires a district court to admit opinion evidence that is connected to existing data only by the ipse dixit of the expert.” See How the models work and The rate decides. This Institute publishes no rate, growth figure or range.
Why do assumptions an expert did not test draw a challenge?
Because Rule 702(b) asks what the expert relied on, and an untested premise supplied from outside the analysis is where the relied-upon facts run out. EcoFactor, Inc. v. Google LLC, 137 F.4th 1333 (Fed. Cir. 2025) (en banc) is the cleanest recent illustration. The damages expert derived a per unit royalty from three prior lump sum settlement licenses, relying on a “whereas” recital in each stating what the patentee believed about its own royalty calculation. The en banc court held that “a fundamental premise of Mr. Kennedy’s testimony—that Daikin, Schneider, and Johnson agreed to pay the $X rate—was not based on sufficient facts or data, as required by Rule 702(b),” because reliance on the unilateral recitals “was untethered from the licenses and unsupported by the evidence on which Mr. Kennedy relied.” It reversed the denial of a new trial and remanded for a new trial on damages.
Two sentences there do more work than the result. The first narrows the field of inquiry: “Rule 702 requires the expert’s relied-upon facts or data—not the record as a whole—to constitute a sufficient basis for the expert’s testimony.” Evidence elsewhere in the file that would have supported the premise does not rescue an expert who did not rely on it. The second describes an unsupported premise from an interested source: of the patentee’s chief executive’s testimony about how the lump sums were calculated, the court said that “[i]n the absence of any evidence, [his] testimony amount[ed] to an unsupported assertion from an interested party.”
One caution about how this ground is usually described. The shorthand is that a damages expert was excluded for adopting assumptions supplied by counsel, and the Institute did not verify a federal appellate decision from 2024 to 2026 resting on that phrase, so it is not asserted here. A premise carried into the model without evidence the expert relied on is a Rule 702(b) problem whatever supplied it.
What happens when the model does not fit the liability theory, or does not apportion?
Fit is a separate requirement from reliability, and a model can be competently built and still measure the wrong thing. The Supreme Court stated the rule in Comcast Corp. v. Behrend, 569 U.S. 27 (2013), decided March 27, 2013: “any model supporting a ‘plaintiff’s damages case must be consistent with its liability case, particularly with respect to the alleged anticompetitive effect of the violation,’” quoting ABA Section of Antitrust Law, Proving Antitrust Damages: Legal and Economic Issues 57, 62 (2d ed. 2010). The expert there had built a regression that, as he acknowledged, did not isolate damages resulting from any one of the four theories of antitrust impact pleaded, only one of which had been accepted for class treatment. What that case decided about certification is treated separately, at Class-wide models.
Apportionment is the same failure viewed from the causal side: attributing to the challenged conduct a result that other things also produced. The Federal Circuit put it plainly in Jiaxing Super Lighting Electric Appliance, Co. v. CH Lighting Technology Co., decided July 28, 2025, which quoted the amended rule and then said that “[i]n the context of patent damages, we have repeatedly explained that the damages expert must apportion among licenses,” and that “expert testimony should be excluded when it fails to allocate license fees among the licensed patents covered by an agreement,” citing MLC Intellectual Property, LLC v. Micron Technology, Inc., 10 F.4th 1358 (Fed. Cir. 2021). The same opinion rejected the usual repair in advance: testimony with an apportionment problem “cannot be justified simply because she made a series of blanket upward and downward adjustments.”
Apportionment is not a patent doctrine, though patent law states it most explicitly. Any measure reading a gap between an actual and a but-for outcome captures whatever else moved in that window: a recession, a lost key employee, a supply interruption, a change in the client’s own strategy. Separating those is the analysis, and an aggregate difference presented as though the defendant caused all of it is the easiest opinion in a case to attack. See The but-for world and Critiquing a model. What a patent, trademark or trade secret claim permits as a measure belongs to the Intellectual Property Institute at iplitigationinstitute.com; what a business or an interest is worth under a governing standard of value belongs to the Business Valuation Institute at businessvaluationsinstitute.com; whether the books themselves are reliable belongs to the Forensic Accounting and Fraud Institute at forensicaccountinginstitute.com.
Which decisions from 2024 to 2026 have applied the amended rule to damages testimony?
Three are worth reading in full, and they do not all run in the same direction. EcoFactor, Inc. v. Google LLC, 137 F.4th 1333 (Fed. Cir. 2025), decided en banc on May 21, 2025, reversed the denial of a new trial on damages, holding that the licenses the expert relied on “were insufficient, individually or in combination, to support his conclusion that prior licensees agreed to the $X royalty rate and therefore the district court abused its discretion in failing to exclude this testimony.” Jiaxing Super Lighting Electric Appliance, Co. v. CH Lighting Technology Co., decided July 28, 2025, quoted the amended text directly and, where the district court had denied the Daubert motion without explanation, said it “should have conducted a more exacting analysis” and must consider apportionment on remand.
The amendment is not a one-way ratchet, and ZipBy USA LLC v. Parzych, Nos. 24-1494, 24-1500, 24-1586, decided by the First Circuit on March 19, 2026, is the case for that. Applying the amended rule to a lost profits opinion built partly on pre-pandemic projections whose own author later disclaimed them, the court held that the district court “did not abuse its discretion in finding that Scally was qualified to testify and that his opinion was based on sufficient factual information,” and observed that “Daubert makes no ‘demand’ that expert testimony be ‘unassailable.’” Read together, the three say that the amendment did not create a new ground of attack on damages testimony; it relocated an existing one, from a jury argument about weight to a question the proponent answers to the court first. Nothing here states what any court will do, and nothing here is legal advice. The exclusion record itself is at Daubert challenges to damages experts.