Overview
Admissibility is a threshold question, and it is not the jury’s. Under FRE 104(a) the court decides preliminary questions about whether a witness is qualified and whether evidence is admissible, and in deciding them it is not bound by the evidence rules except those on privilege. The party offering the opinion carries the burden, and carries it by a preponderance of the evidence. Everything else in this part of the site is a variation on that one allocation: who has to establish what, to whom, on what record, and by which procedural vehicle.
The material divides into three groups, and they answer different questions. The federal framework says what has to be established. The state material says whether that framework is the one that applies. The motions material says how the question gets raised and decided in a real case. A reader who has the first without the second can be entirely correct about federal law in a courthouse where it does not govern; a reader who has both without the third has a position and no vehicle for it.
The federal framework
In federal court the governing text is FRE 702 as amended effective 1 December 2023. It permits a witness qualified by knowledge, skill, experience, training or education to testify in the form of an opinion if the proponent demonstrates to the court that it is more likely than not that the expert’s specialized knowledge will help the trier of fact, that the testimony is based on sufficient facts or data, that it is the product of reliable principles and methods, and that the expert’s opinion reflects a reliable application of those principles and methods to the facts of the case.
Four elements, four separate showings. Courts routinely admit some of an expert’s opinions and exclude others, which is what happens when a witness clears three of the four on a particular subject and not the fourth.
The case law is the Daubert trilogy. Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), held that the Federal Rules of Evidence, not Frye, supply the standard, and that the trial judge has a gatekeeping obligation as to reliability and relevance. 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 conclude there is simply too great an analytical gap between the data and the opinion offered. Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999), held that gatekeeping reaches technical and other specialized knowledge and not only science, and that the trial court has broad latitude in deciding how to test reliability.
Two chronological facts get collapsed constantly. Daubert was decided under a version of Rule 702 that contained none of the reliability criteria now at (b), (c) and (d); those were added effective 1 December 2000. And the amendment effective 1 December 2011 was restyling only, with no substantive change.
What the 2023 amendment did and did not do
The 2023 amendment restated rather than replaced. The Advisory Committee described it as correcting judicial error, not raising a bar: many courts had held that the sufficiency of an expert’s basis and the application of the expert’s methodology were questions of weight rather than admissibility, and the Committee said in terms that those rulings were an incorrect application of Rules 702 and 104(a). The preponderance burden itself was not new — it came from Rule 104(a) and had been stated in the Committee note to the 2000 amendment. It sat in a note for twenty-three years while case law grew up around the rule’s silence.
The note also cuts against reading the amendment as uniformly pro-exclusion. It states that nothing in the amendment imposes any new, specific procedures, and that it does not require a court to make a reliability finding in the absence of objection. Both sides of a motion now cite the same amendment, and both can point to language supporting the characterization they need.
The states, which are not one thing
Frye v. United States, 293 F. 1013 (D.C. Cir. 1923), is a two-page opinion of the Court of Appeals of the District of Columbia — not a Supreme Court decision — arising from a systolic blood pressure deception test offered by a murder defendant. Daubert displaced it federally on textual grounds. It did not overrule it, because a 1923 D.C. panel decision was never binding on any state.
The country is not split into two camps. A large majority of states apply Rule 702 or something functionally identical. A small group — California, Illinois, Minnesota, New York, Pennsylvania and Washington — still runs general acceptance as a gate on novel scientific methodology, several of them alongside a separate reliability inquiry that has nothing to do with general acceptance. And a substantial middle group has its own articulated standards that fit neither label. Charts move slowly and are frequently wrong: Florida has applied Daubert since 2019, the District of Columbia moved in 2016, New Jersey in 2018 for civil cases and 2023 for criminal, and Maryland in 2020.
Neither standard is simply stricter. General acceptance is easy to satisfy for an old, entrenched, poorly validated method and impossible to satisfy for a genuinely new one; the reliability inquiry reverses both. The largest practical difference falls on the experience-based, non-scientific expert, whom Kumho Tire brought squarely inside federal gatekeeping while most general-acceptance jurisdictions never applied their test to that witness at all. And the 2023 amendment reaches a state only if that state amends its own rule.
How the question actually gets raised
The third group is procedural. An objection to expert testimony arrives as a motion in limine, as a separate motion directed at reliability, as voir dire of the witness before the opinion is given, or as an objection at trial. No hearing is required — Kumho Tire gives the trial court the same latitude in deciding how to test reliability as it has in deciding whether the testimony is reliable — and many courts decide on the papers. The vehicle chosen determines the record the ruling is made on, and the record determines what survives review, which is conducted for abuse of discretion.
Published