Blog 702, generally an excellent resource for Rule 702-related matters, rather harshly condemns my theory that Rule 702 is stricter than the the Daubert trilogy. Here's what Joiner says about methodologies and conclusions:
Note the permissive language, backed up by an abuse of discretion standard.
But conclusions and methodology are not entirely distinct from one another. Trained experts commonly extrapolate from existing data. But 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. A court may conclude that there is simply too great an analytical gap between the data and the opinion proffered.
Now, compare Rule 702, as amended, stating "a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise... if ... "the testimony is the product of reliable principles and methods, and the witness has applied the principles and methods reliably to the facts of the case." Note the lack of permissive language; courts must exclude evidence if an expert has not applied the principles and methods reliably to the facts of the case.
Similarly, Kumho Tire seems to give district courts almost infinitely wide discretion in how to determine the admissibility of experience-based testimony, including giving an example of a perfume-sniffer who is to be qualified based solely on experience and "whether his preparation is of a kind that others in the field would recognize as acceptable." Contrast this, again, with Rule 702's absolute requirement that all expert testimony be "the product of reliable principles and methods," that courts must ensure that "the witness has applied the principles and methods reliably to the facts of the case." Arguably, merely asking a perfume sniffer if "his preparation is of a kind that others in the field would recognize as acceptable" doesn't meet this standard.
Finally, Daubert itself was very ambiguous, and there was a great debate over whether it was a "loose scrutiny" or "strict scrutiny" opinion. Joiner and made it clear that Daubert was to be interpreted rather strictly with regard to scientific evidence, Kumho Tire made it clear that a reliability test applies to all expert evidence, and Rule 702 made things even stricter. For courts to go back and assume that any stray dicta is Daubert is sound simply ignores what has happened since then. Unfortunately, what many courts have been doing, in my view, is deciding based on their own predilections whether they want to admit challenged evidence, and then they go back and find precedents that support their perspective, instead of starting with an analysis of Rule 702's requirements, and then deciding whether the evidence meets that standard.
[cross-posted at the Volokh Conspiracy]