The 2023 amendments to Rule 702 didn’t invent new law so much as they forced courts to do what Daubert always required but many were quietly avoiding. If you’ve been filing or opposing expert challenges in the last few years, you’ve probably noticed that the amendment has sharpened the conversation around what the judge is actually deciding at the admissibility stage. Here’s what changed, what stayed the same, and where it’s going to matter most in your practice.
The Rule, As It Now 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.
What the 2023 Amendment Actually Changed
Two things were amended, and both matter. First, the rule now explicitly states that the proponent must demonstrate admissibility by a preponderance of the evidence, spelled out as “more likely than not.” That language wasn’t in the pre-amendment text. Second, subsection (d) was revised to make clear that the court must evaluate whether the expert’s opinion reflects a reliable application of the principles and methods to the facts, not just whether the methodology is reliable in the abstract.
The Advisory Committee’s note is direct about the motivation: too many courts were treating Daubert gatekeeping as a threshold formality and then deferring everything else to the jury. The amendment was a corrective. The committee specifically called out courts that were admitting expert testimony and leaving reliability questions entirely to the jury, without the judge ever vetting whether the expert’s application of the methodology was sound.
The Preponderance Piece: Why It Wasn’t Obvious Before
The preponderance standard for preliminary questions of admissibility already existed under Rule 104. Daubert v. Merrell Dow Pharmaceuticals, Inc. itself acknowledged that Rule 104(a) governs these determinations. But in practice, courts drifted. Some framed the analysis as asking only whether the expert was “minimally qualified” or whether disputes about the basis for an opinion went to weight rather than admissibility. The 2023 amendment puts that framing to rest, at least on paper. The proponent carries an affirmative burden to demonstrate reliability by a preponderance, not just to avoid a clear showing of unreliability.
This is a real shift in how you should think about your Daubert briefing. If you’re the proponent, you’re not just defending your expert from attack. You’re affirmatively making a showing. That means your opposition to a Daubert motion should read more like a brief on the merits of reliability, with citations to the record, the expert’s report, and supporting literature, rather than a brief arguing that the objections go to weight.
The “Reliable Application” Fix in Subsection (d)
This is the part of the amendment that gets underappreciated. The old text required that the expert “apply” the principles and methods “reliably to the facts.” Courts read that as a methodology question. If the general methodology was sound, the application quibbles went to the jury.
The new text requires that the opinion itself reflect a reliable application. The committee’s note is explicit: a court cannot simply accept that a methodology is valid and then wave through the conclusions without examining whether the expert actually followed it. If your expert used a generally accepted differential diagnosis method but skipped steps, cherry-picked data, or reached a conclusion that the methodology wouldn’t actually support, that’s now squarely a judge question, not a jury question.
In toxic tort, products liability, and damages cases, this is where the amendment has the most bite. Opposing an expert on, say, lost profits who used a discounted cash flow analysis? You now have a much stronger argument that the court needs to examine whether the specific inputs and assumptions reflect reliable application, not just whether DCF is a recognized method.
The Common Mistake: Conflating Weight and Admissibility
The most persistent error I see is treating Daubert as a motion about the quality of the expert’s credentials or the general acceptance of a field, while conceding that specific methodological problems are “for the jury.” That framing was always wrong under Daubert, but courts let it slide. Post-amendment, that argument has less traction.
The committee note directly addresses this: “the fact that an expert may be qualified, and may have used a sound method in general, does not mean the court should admit opinions that are the product of an unreliable application of that method.” If you’re opposing expert testimony and you have good record evidence that the expert’s analysis is methodologically unsound at the application level, don’t back off that argument by saying “we understand this goes to weight.” Press it as an admissibility issue, because that’s what it is.
Practical Checklist for Your Next Daubert Motion
When you’re putting together a Daubert motion or opposition under the amended rule, structure your analysis around the four subparts, but focus your fire on (b) and (d). Courts are most receptive to challenges about whether the expert had sufficient data and whether the specific opinions were reliably derived from the methodology used. General attacks on a field or method are harder to win.
- For (b), get into the expert’s reliance materials and identify gaps, particularly data the expert had access to but didn’t use
- For (d), compare what the methodology requires with what the expert actually did, step by step
- Frame your brief around the preponderance standard: what has the proponent shown, and is it enough
- Use the committee note; courts that haven’t fully internalized the amendment respond to it
One more thing worth knowing: several district courts and circuit courts have already signaled that they’re taking the amended language seriously. Courts across multiple circuits have cited the amendment in rulings that excluded experts for application-level failures that might have cleared the bar before 2023. The trend is real, and your briefing should reflect it.