Thursday, March 23, 2006

Damn Dixit

Steve Minor has pointed us to an article on expert evidence in the March 2006 Tennessee Bar Journal by Brian Jackson, a Nashville attorney whose practice includes products liability defense. Entitled "Ipse Dixit by Another Name," the piece reacts to the Tennessee Supreme Court's decision in Brown v. Crown Equip. Corp., No. W2002-02228-SC-R11-CV (Oct. 27, 2005), which overturned the trial court's exclusion of the plaintiff's design defect evidence in a forklift injury case.

These forklift cases, in which Crown Equipment Corporation is recurrently a defendant, tend to fit a certain mold. The worker is injured and brings a products suit against Crown. The worker's engineering expert opines that the injury might have been prevented or mitigated had the forklift boasted a door (or some other design feature). The trial court excludes the engineer's testimony as unreliable, commonly applying Daubert's standards for scientific evidence with unusual zeal: it is customary to hear that the engineer has never designed any forklifts (or any forklifts of the particular kind at issue), has offered no drawings (or only inadequate ones), has conducted no tests (or only inadequate ones), has cited no published peer-reviewed literature (or not enough of it), and has not shown that his opinions are generally accepted by the design, manufacturing, and/or regulatory communities. Having excluded the plaintiff's evidence on defective design, the trial court then awards judgment to the defendant, and the appellate court affirms. See, e.g., Dhillon v. Crown Controls Corp., 269 F.3d 865 (7th Cir. 2001); Bourelle v. Crown Equip. Corp., 220 F.3d 532 (7th Cir. 2000).

The forklift companies, in short, have a certain strategy for winning these cases, and the strategy usually works. In its Brown decision, however, the Tennessee Supreme Court has now thrown a wrench into the works, holding that the trial court applied the "Daubert factors" too mechanically and stringently to the plaintiff's engineering testimony. Mr. Jackson's article sees this as a portent that Daubert may be headed toward toothlessness in Tennessee. We see the Brown decision more as reaching a narrow and sensible conclusion: viz., that the so-called "Daubert factors" have limited application to engineering testimony in design defect cases, and that such evidence is generally better handled under Kumho Tire's rubric for "experience-based" expert testimony.

There are disciplines, like engineering, that make frequent use of scientific information and scientific tools, but whose primary methods of inquiry and analysis are not reducible to the "scientific method" as that concept is generally understood. We may sometimes refer to these disciplines with the honorific, as when we speak of "the science of psychology" or "the science of medicine," and surely there's nothing wrong with the generous spirit in which the compliment is bestowed -- so long as it's remembered that these fields also embody elements of judgment and imperfectly codified practical knowledge to a degree that "harder" sciences do not (or profess not to). Depending on the testimonial occasion, the hybrid character of these fields can often mean that the "Daubert factors" are not suitable for use in evaluating testimonial reliability. But that doesn't mean, as the defense bar sometimes implies, that the testimony is governed by no standards at all. It means only that the governing standards for intellectual rigor are not those of the sciences, but must be gleaned by reference to the standards prevailing within the field in question as it is normally practiced (as Kumho Tire teaches).

Listen carefully, please, because we're going to say it one more time. Daubert promised you that there would be certain standards for expert scientific testimony. It did not promise you that all expert testimony would be scientific.

P.S. While we're at it: "Ipse dixit" is a Latin expression loosely translatable as "he himself said it." It is used in idiomatically correct fashion to refer to an expert opinion for which substantially no defense is offered, other than the expert's invocation of his personal or professional authority. It is not correctly used in reference to opinions for which a reasoned defense is tendered.

A few other things that "ipse dixit" is sometimes used to mean, but which it does not mean: (1) the logic of the expert, or of the expert's discipline, does not constrain inquiry to a unique conclusion; (2) the expert's conclusion is not falsifiable by experimental test; (3) the expert's views run contrary to the weight of official opinion; (4) the expert has relied on some premise or principle for which he cites no published authority; (5) the expert has advanced some thesis that could be restated as a hypothesis susceptible to statistical investigation, but in support of which the expert has offered no statistical analysis. All of these may sometimes be valid criticisms of expert opinion. But the term "ipse dixit" doesn't capture them.

The malapropistic use of "ipse dixit" in modern evidentiary parlance (with which Mr. Jackson's article flirts, without quite embracing it) has a known provenance. It can be traced directly to a passage from Chief Justice Rehnquist's majority opinion in the Joiner decision:
Respondent points to Daubert's language that the "focus, of course, must be solely on principles and methodology, not on the conclusions that they generate." He claims that because the District Court's disagreement was with the conclusion that the experts drew from the studies, the District Court committed legal error and was properly reversed by the Court of Appeals. 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.
We suspect that the textual proximity and conceptual affinities of "ipse dixit" and "analytical gap" in this passage render it vulnerable to misreading, helping to foster the widespread confusion of the two concepts. Once that confusion has taken root, it can be compounded by a mindset that tends to discount all "nonscientific" species of rationality. Every "nonscientific" inference looks, to those in the grip of this mindset, like an "analytical gap." Given the false equation between "analytical gap" and "ipse dixit," it's a short step from there, via transitivity, to the conclusion that all nonscientific inference must be ipse dixit.

That's one of the problems with a bricolage style of legal argumentation, in which the lawyer simply mixes together whatever rhetorical ingredients may be ready to hand and then stirs vigorously. It can lead to mixed-up conclusions.


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Fed. R. Evid. 702: 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, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.