The Daubert Standard

What the Supreme Court decided in 1993

Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), was decided by the Supreme Court of the United States in an opinion by Justice Blackmun. The question presented was whether the Frye general-acceptance test, which had governed novel scientific evidence in the federal courts for decades, survived the enactment of the Federal Rules of Evidence. It did not: “The Federal Rules of Evidence, not Frye, provide the standard for admitting expert scientific testimony in a federal trial.” 509 U.S. at 585.

Displacing Frye did not leave expert evidence unscreened, and the opinion said so in the same breath. “That the Frye test was displaced by the Rules of Evidence does not mean, however, that the Rules themselves place no limits on the admissibility of purportedly scientific evidence. Nor is the trial judge disabled from screening such evidence. To the contrary, under the Rules the trial judge must ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable.” 509 U.S. at 589. That sentence is the origin of the gatekeeping obligation, and it is the part of the decision that survived every later amendment to the rule.

The disposition was narrow. The judgment below was vacated and remanded so that the correct standard could be applied; the Court did not apply it to the record itself. Nor was the opinion unanimous throughout. Chief Justice Rehnquist, joined by Justice Stevens, concurred only in the opening portions of the opinion — agreeing that the Rules superseded Frye — and dissented from the remainder, objecting that the Court’s general observations about reliability were unnecessary to the decision and vague as guidance for district judges.

The rule the Court was construing no longer reads that way

This is the fact most often missing from summaries of the case. Rule 702 in 1993 contained none of the reliability language a reader will find in it today. It read, in full:

“If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.”

There was no subsection (a), (b), (c) or (d). The Court derived the gatekeeping obligation from two phrases in that single sentence — scientific … knowledge, and assist the trier of fact. The requirements that the testimony be based on sufficient facts or data, be the product of reliable principles and methods, and reflect a reliable application of those methods were added to FRE 702 effective 1 December 2000, in response to Daubert and to Kumho Tire. The amendment effective 1 December 2011 was part of the general restyling of the Federal Rules of Evidence and changed nothing of substance. The amendment effective 1 December 2023 put the burden of proof on the face of the rule and rewrote subsection (d).

So the phrase the Daubert rule describes a body of law, not a provision. The decision supplies the gatekeeping obligation and a set of reliability considerations; the operative text an attorney briefs is FRE 702 as amended, and a brief that quotes the 1993 rule as though it were current is quoting a rule that was superseded a quarter of a century ago.

Where the gatekeeping obligation comes from

Two textual hooks did the work. On the first, the Court wrote that “[t]he subject of an expert’s testimony must be ‘scientific … knowledge,’” and that “[t]he adjective ‘scientific’ implies a grounding in the methods and procedures of science.” 509 U.S. at 590. That is the reliability half. The requirement that the testimony assist the trier of fact supplied the second half, which the opinion described as a question of fit — whether the reasoning or methodology properly applies to the facts in issue.

The procedural home of the inquiry is FRE 104(a): “The court must decide any preliminary question about whether a witness is qualified, a privilege exists, or evidence is admissible. In so deciding, the court is not bound by evidence rules, except those on privilege.” Two consequences follow, and both matter in practice. The admissibility question belongs to the judge rather than the jury. And because the court is not bound by the rules of evidence in deciding it, the record on a challenge is routinely built from the expert’s report and deposition transcript, which are themselves hearsay and would not be admissible at trial.

What the decision did not hold

The case is cited for propositions it does not contain more often than almost any other in the Federal Reporter system. It did not:

• hold the plaintiffs’ experts inadmissible. The Court vacated and remanded for application of the correct standard and did not evaluate the proffered testimony;
• adopt a test or a checklist. The considerations it identified were introduced with the words “Many factors will bear on the inquiry, and we do not presume to set out a definitive checklist or test.” 509 U.S. at 593;
• address non-scientific expertise. The opinion speaks of scientific knowledge throughout. Whether the obligation reached technical and other specialized knowledge was open until Kumho Tire in 1999;
• set the standard of appellate review. That came from Joiner in 1997;
• bind state courts. The opinion construes the Federal Rules of Evidence;
• require a hearing. Nothing in the opinion, in FRE 702 or in FRE 104 obliges a court to take live testimony before ruling.

The standard as the rule now states it

An attorney arguing admissibility today argues the rule, with the case law behind it. FRE 702, effective 1 December 2023, provides:

“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 preponderance language is what the 2023 amendment added, and the Advisory Committee was explicit that it was codifying the standard FRE 104(a) had always supplied rather than raising it. The 2000 Committee Note had already said the same thing: “the proponent has the burden of establishing that the pertinent admissibility requirements are met by a preponderance of the evidence.” The proponent carries that burden on every element — qualification, helpfulness, basis, method, and application — not merely on the ones the opponent chooses to attack.

Reliability is a lower bar than correctness

The gatekeeping inquiry does not ask the judge to decide which expert is right. The Advisory Committee made the point by quoting In re Paoli R.R. Yard PCB Litigation, 35 F.3d 717, 744 (3d Cir. 1994): proponents “do not have to demonstrate to the judge by a preponderance of the evidence that the assessments of their experts are correct, they only have to demonstrate by a preponderance of evidence that their opinions are reliable. … The evidentiary requirement of reliability is lower than the merits standard of correctness.”

The Committee added the corollary in 2023: where qualified experts reach different conclusions from contested sets of facts, the standard “does not necessarily require exclusion of either side’s experts” — the jury decides the disputed facts and decides whom to credit. That is the same allocation the 1993 opinion described when it identified the remedy for weak testimony that clears the bar: “Vigorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof are the traditional and appropriate means of attacking shaky but admissible evidence.” 509 U.S. at 596.

What that sentence does not do is convert every reliability objection into a jury question. The Committee’s 2023 Note is directed at courts that read it that way, and the amended preamble was written to remove the textual room for the argument.

Which courts are bound

The decision construes the Federal Rules of Evidence and controls in federal court. It has no direct effect in a state that has not adopted it. Most states have moved to Daubert or to a standard resembling it, a minority retain Frye or a state-specific formulation, and several have moved between the two by legislation or by rule amendment rather than by decision. The practical consequence is that the phrase the Daubert standard is incomplete without a forum: the same expert, the same report and the same method can face materially different admissibility law depending on where the case is filed and, in a removed case, on where it ends up.

The two decisions that completed the framework

Read alone, the 1993 opinion leaves two large questions open, and the Supreme Court answered both within six years.

General Electric Co. v. Joiner, 522 U.S. 136 (1997) held that a ruling admitting or excluding expert evidence is reviewed for abuse of discretion, and that a court may exclude an opinion whose connection to the underlying data rests on the expert’s say-so: a court “may conclude that there is simply too great an analytical gap between the data and the opinion proffered.” 522 U.S. at 146.

Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999) held that the gatekeeping obligation “applies not only to testimony based on ‘scientific’ knowledge, but also to testimony based on ‘technical’ and ‘other specialized’ knowledge,” and that the trial court has broad latitude in deciding how to test reliability as well as whether the testimony is reliable.

Those three decisions are conventionally called the Daubert trilogy, and the reliability requirements added to FRE 702 in 2000 were drafted to codify them. Primary text: the opinion at 509 U.S. 579 and Rule 702 with its Committee Notes.

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Published 2026-08-12