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Resolving Daubert Challenges

Rule 26(e) -- Supplementing the Report

    Under Fed. R. Civ. P. 26(e), parties are required, on penalty of preclusive sanctions, to supplement all expert reports (and discovery responses), on their own initiative, if they learn that "in some material respect the information [previously] disclosed is incomplete or incorrect and if the additional or corrective information has not otherwise been made known to the other parties during the discovery process or in writing."

    This is an anti-surprise rule.  If an expert's opinion changes in a material way, or if the expert plans to opine on some new topic, the adversary is entitled, under the rules, to seasonable notice.  If a good-faith effort at supplementation fairly places the adversary on notice of any changes, the courts will ordinarily allow the testimony.  Preclusive sanctions are generally applied only where the adversary received no actual notice and has suffered prejudice as a result.

Defensive and Offensive Uses

    Counsel generally see supplementation as a defensive measure, undertaken to avoid exclusion of their experts' testimony.  But the rule also has its offensive uses, because supplementation is a vehicle by which counsel may correct or improve their expert reports in light of later-acquired information.

    And later information will emerge, despite the best efforts of counsel and expert to perfect the expert's analysis and exposition in the original report.  New information may involve either the expert's opinions or the expert's "bases and reasons" for those opinions, and it can come from many sources.  It may come from additional research or reflection, or from additional data or evidence of which the expert was previously unaware.  It may even come -- and this is important  -- from the adversary's objections to the expert's testimony.

    An expert may find, for example, that the expert's original opinion stands in need of qualification or refinement to accommodate some putative analytical flaw or counterexample offered by the opposition.  A vaguely or ambiguously stated conclusion may require clarification to avert misinterpretation.  A trivial mathematical error may need to be fixed before the opposition uses it to devastating effect.  A learned treatise trotted out by the adversary may need to be placed in context.  Or criticisms from the adversary's own experts may require response.

      If it is expected that the expert's testimony will be challenged under Daubert, a formal supplemental report under Rule 26(e) represents an attractive medium in which to effect such revisions.  As with the original report, the process of drafting the supplemental material imposes a certain discipline on both counsel and the expert.  Moreover, the proponent can frame any revisions in the proponent's own terms, rather than letting the adversary set the intellectual agenda.  Finally, any risk of preclusive sanctions is minimized, because the litigants will not get bogged down in disputes over whether some hastily chosen phrase in the expert's deposition testimony (or a letter from counsel) represents adequate disclosure.  The proponent will be able to point to a formal document reflecting exactly the testimony that the expert will give.

Format of the Supplemental Report(s)

      If a supplemental report is served, consideration should be given to serving a full revised edition of the entire report (along with a redlined version to identify the changes).  At the very least, it may be desirable to serve such an integrated revised edition at the final deadline for supplementation, when it is known that no further revisions will be forthcoming.  Rule 26(e), to be sure, does not require any such integrated restatement of the expert's report.  Indeed, the rule does not impose any particular format on supplementation at all.  But a full second (or third) edition will ensure that the expert's work is still embodied in a single, self-contained document, which will often enhance both the report's legibility and the expert's credibility.

    Look at it this way.  If you were a judge or juror, would you want to shuffle through a pile of baffling errata sheets and epistolary emendations and deposition transcripts in a futile search for a clear and self-contained statement of the expert's ultimate position?

Timing of the Supplemental Report(s)

    Rule 26(e) does not require supplementation every time an expert hiccups.  Supplementation must be made at "appropriate intervals," which may be set by the court.  The final deadline for supplementation is set in Rule 26(e)(1) to coincide with the deadline for disclosure of witness lists and trial exhibits under Rule 26(a)(3).  The Rule 26(a)(3) deadline, in turn, is whenever the court says, or, if the court sets no explicit Rule 26(a)(3) deadline, thirty days before trial.  It is not clear, from the text of Rule 26, whether the court may set the supplementation deadline earlier than the Rule 26(a)(3) deadline.  The rule's own language does not seem to confer such discretion in express terms, but Fed. R. Civ. P. 16(b)(4) does speak of "modifications of the times for disclosures under Rules 26(a) and 26(e)(1)."  It is always risky, in any event, to act on a stingy estimate of the trial court's inherent authority.

The "Moving Target" Concept

    Some restraint should be shown in supplementation.  Overly frequent modifications of an expert's opinion will undercut the expert's credibility, and overt floundering may well doom the expert under Daubert.  At a minimum, the price of any major revision is likely to be a new deposition of the expert.  And as trial approaches, wholesale revisions will often be greeted with very finite judicial patience.

    That said, strong arguments can be made for special tolerance of good-faith revisions to expert testimony.  By definition, such testimony involves matters of scientific or technical opinion, as opposed to brute observational fact, and for many reasons, it is the nature of the beast that as research and investigation progress, the expert's opinions will evolve.  Indeed, there would be grounds for worry if they didn't.  If there is any methodological canon of general applicability across all domains of inquiry, it is, perhaps, that investigators should be willing to adjust their analyses and opinions in light of emergent evidence -- and to meet or accommodate criticism and objections.

    Nevertheless, when an expert's views evolve over time, and especially when experts qualify their views in response to the opposition's objections, adversaries and even judges will sometimes complain that the expert presents a "moving target."  The use of this expression must strike many academic experts, in particular, as peculiar.  In the academy, after all, intellectual flexibility is often regarded more as a virtue than as a vice, and many experts will naively suppose that they were retained to provide enlightenment and assistance -- not to supply a stationary "target" at some lawyerly shooting range. 

    The truth is that nothing in Daubert requires experts to exhibit dogmatic fixity in the face of criticism.  To be sure, some experts may change their views as often as they change their socks, to the legitimate frustration of adversaries trying to anticipate the experts' ultimate testimony, as well as that of judges trying to promote an eventual resolution of the controversies before them.  But this should not be viewed, in general, as a Daubert problem.  In most cases where experts bob and weave to arguable excess, juries can and should be trusted to notice.  On the rare occasion when an expert has so frequently or so radically reinvented himself that no jury could reasonably credit his testimony, it may be permissible to exclude the testimony as "misleading" under Fed. R. Evid. 403 or to discount it on a motion for summary judgment.  If the bobbing and weaving has unfairly increased the adversary's discovery costs, the courts can often shift some or all of those costs to the proponent.  And if the bobbing and weaving continues to trial, judges can enforce the rules by tethering the testimony to the expert's final report and/or the proponent's final pretrial statement, evaluating its admissibility in that context.

     Plenty of remedies already exist, in short, for dealing with gamesmanship.  The Daubert inquiry is about something different -- viz., whether the expert's analysis is valid.  The fact that an expert has refined his or her opinion in successive iterations does not, by itself, cast doubt on the validity of the expert's views.  Quite the contrary, it may be an affirmative indicium of reliability.  Theories, after all, are supposed to be adjusted in response to new data or analytical objections.  For Daubert purposes, the real question is whether the testimony, as thus adjusted, satisfies the pertinent reliability criteria.

Rule 16
The Report
Special Masters
Motions in Limine
Rule 56
Model Local Rule