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Developments in MDL: Subcommittee Sketches a New Rule 16.1

Andrew Jackson, Hannah R. Anderson, and Emilie Erickson


  • Multidistrict litigation (MDL) has become the preferred battleground for civil litigation in U.S. federal courts, comprising over 70 percent of the federal civil caseload by the end of 2021.
  • The Federal Rules of Civil Procedure currently do not mention MDLs, leading to procedural abuse and unpredictability in the MDL process.
  • The Advisory Committee on Civil Rules formed the Multidistrict Litigation Subcommittee to explore potential changes to address the challenges posed by MDLs.
  • The subcommittee has proposed a new rule, Federal Rule of Civil Procedure 16.1, focused on encouraging early exchange of information and appointment of plaintiffs' leadership counsel.
Developments in MDL: Subcommittee Sketches a New Rule 16.1
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Lawyers love getting the last word, whether they are seeking leave to file a sur-sur-sur-surreply (which actually happened, see United States ex rel. Hockett v. Columbia/HCA Healthcare Corp., 498 F. Supp. 2d 25 (D.D.C. 2007)) or interjecting the umpteenth “last” comment at oral argument. In pharmaceutical and medical device cases, plaintiffs’ counsel frequently try to “fix” problems with their cases through the ever-popular “rebuttal” or “supplemental” expert report. Often such rebuttal reports are served after the defendant manufacturer has laid out its defense in its expert reports or in a motion for summary judgment. Other times, plaintiffs have simply lost faith in their affirmative expert, due perhaps to a successful Rule 702 challenge in another jurisdiction or by virtue of the expert’s crash-and-burn performance at deposition. In any event, improper or untimely rebuttal expert reports prejudice the opposing party by necessitating further costs and delay in the form of additional depositions and potentially supplemental expert reports in response.

The Rules Relating to Rebuttal or Supplemental Expert Reports

Federal Rule of Civil Procedure 26(a)(2)(D) requires parties to disclose expert reports “at the time and in the sequence that the court orders.” Federal courts have discretion over discovery determinations, including whether to exclude improper expert reports. In addition, Federal Rule of Civil Procedure 37(c)(1) states that “[i]f a party fails to provide information or identify a witness as required by Rule 26(a) or (c), the party is not allowed to use that information or witness to supply evidence on a motion, at a hearing, or at trial, unless the failure was substantially justified or harmless.”

Common Improper Rebuttal Experts

The untimely expert. If counsel finds himself or herself in the unenviable position of needing an extension of time for an expert report, the court may grant an extension under Federal Rule of Civil Procedure 6(b)(1). The good cause needed to obtain an extension is not a high bar, if sought before the deadline passes. Once the deadline has passed, Rule 6(b)(1)(B) permits an extension only on a showing of both good cause and excusable neglect. If the plaintiff is seeking to modify a court’s scheduling order but does so only after missing a deadline, Federal Rule of Civil Procedure 16(b)(4)’s good cause requirement imposes a significantly heavier burden than the good cause required under Rule 6, and the inquiry focuses almost entirely on the diligence of counsel. McCann v. Cullinan, No. 11 CV 50125, 2015 WL 4254226, at *20–21 (N.D. Ill. July 14, 2015).

It is not uncommon for there to be a flurry of late-disclosed case-specific experts after remand, especially in cases remanded from expansive multidistrict litigation cases, in which the majority of the general expert work might be done en masse by plaintiffs’ leadership counsel. Cases return to their transferor courts where judges set aggressive trial schedules on the assumption that the remanded cases are trial-ready. That’s when plaintiff’s counsel realizes they do in fact need their own specific causation expert to testify about the particular plaintiff’s alleged injuries. See, e.g., Atkinson v. Ethicon, Inc., No. 13-697, 2019 WL 3037304, at *2–5 (W.D. Pa. July 11, 2019) (striking plaintiffs’ late-disclosed specific causation expert under Rules 37 and 16 and granting summary judgment where expert was disclosed seven months after the close of discovery in opposition to summary judgment after the court had denied plaintiffs’ request to reopen discovery to disclose an expert).

Sometimes counsel just misses the deadline, and even a short delay can result in exclusion. See Tyree v. Boston Sci. Corp., 2014 WL 5486694, at *58–59 (S.D.W.V. Oct. 29, 2014) (striking rebuttal expert report disclosed 13 days late).

The bolstering, case-in-chief expert. Under Federal Rule of Civil Procedure 26(a)(2)(C), permissible rebuttal expert reports must be “intended solely to contradict or rebut evidence on the same subject matter identified by another party.” “The proper function of rebuttal evidence is to contradict, impeach or defuse the impact of evidence offered by an adverse party.” Peals v. Terre Haute Police Dep’t, 535 F.3d 621, 630 (7th Cir. 2008); see also Marmo v. Tyson Fresh Meats, Inc., 457 F.3d 748, 759 (8th Cir. 2006) (“function of rebuttal testimony is to explain, repel, counteract or disprove evidence of the adverse party”). “Ordinarily, rebuttal evidence may be introduced only to counter new facts presented in the defendant’s case in chief. . . . Permissible rebuttal evidence also includes evidence unavailable earlier through no fault of the plaintiff.” Allen v. Prince George’s Cty., Md., 737 F.2d 1299, 1305 (4th Cir. 1984).

Rebuttal reports that merely bolster the plaintiff’s case in chief or relate to issues on which the plaintiff has the burden of proof, such as causation, are improper because they should have been disclosed with the plaintiff’s initial expert disclosures. See, e.g., Africano v. Atrium Med. Corp., No. 17 CV 7238, 2019 WL 5085338, at *2–4 (N.D. Ill. Oct. 10, 2019) (striking rebuttal expert report as bolstering case-in-chief and duplicative of plaintiff’s already disclosed causation expert and not rebutting defendant’s expert); In re C.R. Bard, Inc., 2013 WL 2432861, at * (S.D.W.V. June 4, 2013) (same); United States ex rel. Higgins v. Boston Sci. Corp., 2021 WL 1661255, at *5 (D. Minn. Apr. 28, 2021) (striking rebuttal expert report as new opinions supporting plaintiff’s affirmative case in chief and not rebutting defendant’s expert).

The unqualified expert. The admissibility of expert testimony is governed by Federal Rule of Evidence 702, which requires 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 has reliably applied the principles and methods to the facts of the case.

Plaintiffs’ counsel occasionally, in the face of (typically) strong defense-side experts, ask one of their experts to go out on a limb to attempt to rebut the reliable, science-based opinions of a well-recognized expert, perhaps in a field outside the plaintiff’s expert’s own.

A Trifecta Ruling

As unusual as it may be, one recent case managed to touch on all three of these improper rebuttal experts in one decision.

In Gravitt v. Mentor Worldwide LLC, No. 17 C 5428, 2022 WL 3584620 (N.D. Ill. Aug. 22, 2022), the plaintiffs in a silicone breast implant case timely disclosed three experts, a rheumatologist, a pathologist, and a chemist. The rheumatologist and pathologist testified that all breast implants are slow delivery systems of toxins that cause systemic illness in patients. The chemist testified about his physical observations of plaintiff Catherine Gravitt’s actual implants, including that one had ruptured. Id. at *1. The defendant timely disclosed seven experts of its own in various scientific and technical fields to rebut the plaintiffs’ experts. Id. The plaintiffs received a six-week extension of time to July 15, 2022, to serve rebuttal expert reports. After requesting a short additional extension (over a weekend), on July 18 the plaintiffs disclosed three “rebuttal” experts: a biostatistician who failed to provide a report; another rheumatologist who echoed the first rheumatologist and pathologist on causation; and the chemist who purported to testify about the regulation of medical devices by the Food and Drug Administration (FDA).

The defendant moved to strike the three “rebuttal” experts on the aforementioned grounds: that the biostatistician’s report was untimely; that the rheumatologist was not a rebuttal expert but a bolstering, case-in-chief expert on causation who should have been disclosed months earlier; and that the chemist was wholly unqualified to provide opinions about the FDA’s regulation of medical devices.

The untimely biostatistician. Plaintiffs’ counsel insisted that the biostatistician had experienced a serious medical condition during the 11 weeks he had to draft his rebuttal report and that the medical condition “confused him” about the deadline and affected his ability to complete his report. The plaintiffs’ opposition included a letter from the expert’s doctor, medical records, and a sworn declaration from the expert. The plaintiffs requested that their expert be granted extra time as an “accommodation” for his “disability.”

The defendant pointed out that the expert’s medical condition affected him for only about 2 of the 11 weeks he had to draft his report; the plaintiffs submitted no evidence that the medical condition actually prevented the expert from completing his report by the deadline.

The court found that the plaintiffs’ delay in serving the biostatistician’s report was inexcusable. Plaintiffs’ counsel notified him on June 2 via email of the July 15 deadline. Plaintiffs’ counsel spoke to the expert on June 23—after his medical event in early June—but “neglected to do what prudence demanded under the circumstances, which was to confirm with him the July 15 deadline.” Id. at *2.

Compounding the error, plaintiffs’ counsel did not immediately move for an extension of time to serve the biostatistician’s late report, despite knowing their expert had been confused about the deadline as of July 14—the day before the deadline—and could not complete his report for several more weeks. Instead, plaintiffs’ counsel “inexplicably” waited 18 days, until August 2, to serve the report and to file a belated request for an extension of time. Id.

The court found that granting a further extension would prejudice the defendant and materially affect the proceedings by delaying the case for months. The court granted the defendant’s motion to strike and denied the plaintiffs’ motion for an extension. The court would have reached the same result under Rule 37(c)(1) and Rule 16(b)(4), because plaintiffs’ counsel was not diligent and the plaintiffs’ delay was neither harmless nor justified. Id.

The bolstering, case-in-chief rheumatologist. Plaintiffs’ counsel argued that a third causation expert was necessary due to the defendant’s expansive expert disclosures that put the issue of silicone toxicity at the forefront of the case. The court disagreed and pointed out that “[i]ndeed, Plaintiffs’ opening experts did make the case for a causal link between [defendant]’s implants and [plaintiff’s] injuries . . . Thus, Plaintiffs themselves recognize that the opinions offered in [the expert’s] rebuttal report were properly grist for an opening expert report.” Id. at *4. Because his opinions went to causation, an issue on which the plaintiffs bore the burden of proof, the expert should have been disclosed in the plaintiffs’ opening disclosures, not in a rebuttal report. “That [the expert’s] report makes a few references to [defendant]’s experts does not make it proper rebuttal.” Id.

While not mentioned in the order, the defendant submitted with its motion to strike two other expert reports the rheumatologist had authored in different cases as a case-in-chief causation expert, and they were largely identical to his “rebuttal” report.

The unqualified chemist. The plaintiffs argued they needed the Canadian chemist—who last worked at the Bureau of Radiation and Medical Devices in Canada’s Department of Health and Welfare in 1989—to counter the defendant’s regulatory affairs expert, who had worked at the FDA for 24 years. The chemist, however, had no U.S. regulatory affairs or FDA experience. The court treated Mentor’s motion to strike as one under Rule 702 and held that the Canadian chemist did not establish that he has “superior knowledge, skill, experience, or education” on the FDA’s regulation of medical devices.


Plaintiffs’ disclosure of rebuttal experts need not be the last word. Rebuttal reports must be timely submitted by qualified experts and offer narrowly tailored rebuttal opinions. Moving to strike noncompliant rebuttal reports before filing a Rule 702 motion can be an effective tool and help avoid the time and cost associated with preparing for unnecessary additional expert depositions and supplemental expert reports.