United States of America ex rel. v. Janssen Biotech, Inc.

UNITED STATES DISTRICT COURT
DISTRICT OF MASSACHUSETTS
__________________________________________
)
THE UNITED STATES OF AMERICA, et al., 	)
ex rel. JULIE LONG, 	)
)
Plaintiffs, 	)
) 	Civil Action No.
v. 	) 	16-12182-FDS
)
JANSSEN BIOTECH, INC., 	)
)
Defendant. 	)
__________________________________________)
MEMORANDUM AND ORDER ON DEFENDANT’S
MOTIONS TO STRIKE SUPPLEMENTAL EXPERT REPORTS
SAYLOR, J.
This is a qui tam action alleging that a pharmaceutical company unlawfully provided
certain services to physicians who prescribed its medications. Relator Julie Long sued defendant
Janssen Biotech, Inc., a company that manufactures and sells Remicade and Simponi ARIA, two
infusible medications used to treat various conditions. She contends that the services constituted
kickbacks in violation of the Anti-Kickback Statute, 42 U.S.C. § 1320a-7b(b), which in turn
resulted in the payment of false claims in violation of the False Claims Act, 31 U.S.C. § 3729(a).
On February 20, 2026, defendant filed a motion to strike the supplemental expert report
of Dr. Meredith Rosenthal, one of relator’s experts. (Dkt. Nos. 551, 552). On March 5, 2026,
defendant filed an “Emergency Motion to Bar Relator from Serving a Second Out-of-Time
Expert Report and to Compel Relator to Seek Leave of Court Prior to Expanding Court-Imposed
Deadlines.” (Dkt. No. 570). Both motions object to certain amendments to Dr. Rosenthal’s
expert report that relator served following the taking of her deposition.
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In essence, the amendments sought to correct certain errors that Dr. Rosenthal made in
her damages calculations in her initial report. The mistakes involved both incorrectly including
certain physician practices in a control group and using the incorrect timing for when the
treatment began. (See Dkt. Nos. 571-1, 571-2). Defendant contends that these corrections are
not minor or technical, but are instead improper attempts to supplement Dr. Rosenthal’s opinions
after defendant pointed out the errors at her deposition.
Two somewhat countervailing principles are at issue here. On the one hand, Rule 26(e)
does not merely permit, but in fact requires, a party to “supplement or correct” an expert report
that is “incomplete or incorrect.” Fed. R. Civ. P. 26(e). At the same time, however, a party
cannot use a “supplemental” expert disclosure as a means to strengthen an expert’s opinion
following potentially damaging deposition testimony. See, e.g., Martinez-Serrano v. Quality
Health Servs. of P.R., Inc., 568 F.3d 278, 283-84 (1st Cir. 2009).
Under the circumstances presented here, and despite considerable misgivings, the Court
will permit the supplementation and will not order that it be struck. Nonetheless, defendant will
be given a fair opportunity to cure any resulting prejudice, with reasonable attorney’s fees and
expenses to be borne by relator.
I. 	Background
Dr. Meredith Rosenthal is a professor of health economics and policy at the Harvard T.H.
Chan School of Public Health. (Dkt. No. 561-4 at 7). She was retained by relator to provide
expert testimony concerning causation—that is, whether the allegedly unlawful services that
defendant provided to certain medical practices caused them to prescribe more of defendant’s
products. She also provided expert testimony as to the value of the claims for those products that
were submitted to Medicare and the damages the government allegedly suffered as a result. (Id.
at 8).
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As relevant here, the deadline for relator to designate her experts and provide their
reports was July 7, 2025, and the deadline for relator to designate any rebuttal experts and
provide their reports was November 26, 2025. (Dkt. Nos. 473, 480). Dr. Rosenthal’s report was
served on July 7, 2025. (Dkt. No. 552 at 2).
Dr. Rosenthal was deposed by defendant on January 22, 2026. (Id.). At the deposition,
defendant’s counsel pointed out several errors in her calculations. (Dkt. No. 552-1 at 5-6, 8).
The first error “relates to two practices that [Dr. Rosenthal] now [understood] received
more than two of the allegedly unlawful site of care programs, thereby making them ineligible to
be part of the control group in [her] model.” (Dkt. No. 571-1 ¶ 2).1 The second error was that
her model apparently treated a practice as being “tainted”—that is, to have been the subject of
the alleged kickbacks—as of the quarter in which it received its first ABS call from defendant,
when she intended the model to treat a practice as “tainted” as of the quarter in which it received
its second ABS call from defendant. (Id. ¶ 3). Correcting those errors also led Dr. Rosenthal to
revise her estimate for the size of the treatment effect and for total damages. (Id. ¶¶ 4-5). The
cumulative effect of the two errors was substantial.
On February 11, 2026, relator served an amendment to Dr. Rosenthal’s initial report,
which corrected the two errors. (Dkt. No. 571-1 at 3).
On February 20, 2026, defendant filed a motion to strike the amendments to the expert
report on the ground that they were untimely and improper under Rule 26. (Dkt. Nos. 551, 552).
On March 5, 2026, relator served a second amendment to Dr. Rosenthal’s report. (Dkt.
No. 571-2). The second amendment sought to correct a further error that was introduced in Dr.
1 In her second amendment, Dr. Rosenthal indicated that this should have read “two or more of the
allegedly unlawful site of care programs,” the result of a “typographical error” on her part. (Dkt. No. 571-2 ¶ 1).
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Rosenthal’s first amendment to her report; she had calculated her damages estimate for two
practices beginning from the first date they received any Site of Care program, rather than the
first date they received an at-issue Site of Care program. (Id. ¶ 2). Correcting that error led Dr.
Rosenthal to adjust downward her damages estimates. (Id. ¶¶ 4-5).
Also on March 5, 2026, defendant filed an emergency motion to bar relator from serving
Dr. Rosenthal’s second amended report. (Dkt. No. 570). Relator opposed both motions on
March 6, 2026, and defendant filed a reply in support on March 10, 2026. (Dkt. Nos. 571, 572).
II. 	Legal Standard
Fed. R. Civ. P. 26(a)(2) governs the disclosure of expert testimony. “[A] party must
disclose to the other parties the identity of any [expert] witness it may use at trial to present
evidence . . . .” Fed. R. Civ. P. 26(a)(2)(A). If the witness “is one retained or specially
employed to provide expert testimony in the case or one whose duties as the party’s employee
regularly involve giving expert testimony,” the party must also submit a “written report” with
numerous detailed facts, data, exhibits, and other items. Fed. R. Civ. P. 26(a)(2)(B).
“A party must make these disclosures at the times and in the sequence that the court
orders.” Fed. R. Civ. P. 26(a)(2)(D). As with all disclosures made under Rule 26(a), parties
must “supplement or correct” their expert disclosures “in a timely manner” if a party learns of an
omission or error unknown to the other party or “as ordered by the court.” Fed. R. Civ. P.
26(e)(1). “For an expert whose report must be disclosed under Rule 26(a)(2)(B), the party’s duty
to supplement extends both to information included in the report and to information given during
the expert’s deposition.” Fed. R. Civ. P. 26(e)(2).
III. 	Analysis
The issue here is whether Dr. Rosenthal’s two amendments are properly considered mere
supplemental reports, which would be permissible as long as they were provided “in a timely
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manner,” or whether they are instead substantively new (and untimely) reports that should be
struck.
It is certainly true that Rule 26(e) does not give parties the freedom to modify expert
reports at will.
Supplementation of an expert report permits a party to correct inadvertent errors
or omissions. Supplementation, however, is not a license to amend an expert
report to avoid summary judgment. Courts distinguish “true supplementation”
(e.g., correcting inadvertent errors or omissions) from gamesmanship, and have
therefore repeatedly rejected attempts to avert summary judgment by
“supplementing” an expert report with a “new and improved” expert report.
8A WRIGHT & M ILLER ’S FEDERAL P RACTICE & P ROCEDURE § 2049.1 (3d ed. 2026) (quoting
Gallagher v. Southern Source Packaging, LLC, 568 F. Supp. 2d 624, 630-31 (E.D.N.C. 2008)).
Stated otherwise, “Rule 26(e) is not a vehicle to permit a party to serve a deficient opening report
and then remedy the deficiency through the expedient of a ‘supplemental’ report.” In re Bear
Stearns Cos., Inc. Sec., Derivative, & ERISA Litig., 263 F. Supp. 3d 446, 451 (S.D.N.Y. 2017)
(citation modified); see also Martinez-Serrano, 568 F.3d at 282-84 (upholding district court’s
decision to exclude expert opinion first disclosed in “final addendum” provided after expert’s
deposition).
On the other hand, courts have found that updates to expert reports that merely “correct[]
mathematical errors that . . . have only a minor impact on the results and do not change the
substantive conclusions” do not violate Rule 26. See Moussouris v. Microsoft Corp., 311 F.
Supp. 3d 1223, 1239-40 (W.D. Wash. 2018) (citation modified). The First Circuit has suggested
that the dividing line lies between “the propagation of a brand-new theory” in a supplemental
report, where “preclusion [is] well within the ambit of the district court’s discretion,” and “a
refinement of an existing theory,” where it may not be. Martinez-Serrano, 568 F.3d at 283-84.
Thus, whether the supplemental reports at issue here are permissible largely turns on whether
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they are better viewed as “refinement[s]” of Dr. Rosenthal’s initial report or whether they are, in
substance, the introduction of an entirely new opinion. Id.
The amendments to Dr. Rosenthal’s calculations are not simply corrections to
arithmetical calculations. The amendments include removing some sites from the control group
and changing the dates from when the treatment effects began to be calculated, both of which are
key elements of the econometric model she created. But they reflect a correction to inputs only;
they are not alterations to her methodology. As a result, in the Court’s view, the amendments are
closer to “corrections of mathematical errors” than to fundamental changes in her opinions. See
Moussouris, 311 F. Supp. 3d at 1239. And that is true despite the fairly large bottom-line impact
of the errors. Accordingly, this does not appear to be a situation in which relator is engaging in
“gamesmanship” in order to avoid summary judgment. 8A WRIGHT & M ILLER ’S FEDERAL
P RACTICE & P ROCEDURE § 2049.1 (3d ed. 2026).
That view is strengthened by the similar decision of another district court under
analogous circumstances. In that case, the plaintiff’s damages expert produced an initial report
that calculated that the plaintiff had suffered a particular amount of damages as a result of the
defendant’s breach of contract. Capitol Justice LLC v. Wachovia Bank, N.A., 706 F. Supp. 2d
34, 37 (D.D.C. 2009). Following the defendant’s deposition of the plaintiff’s expert, the plaintiff
informed the defendant that the expert “was revising his calculation and would submit a revised
report.” Id. at 38. The revised report changed “the inputs and calculations within the damage
model” while keeping the model structure the same. Id. After the defendant challenged the
revised report as an improper supplementation, the court declined to exclude the expert report as
untimely. Id. at 39-40. It reasoned that the report was a proper supplementation under Rule
26(e) because the expert “did not wholly rework his damages claim,” but instead “used the same
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methodology” and simply “changed the inputs and calculations to produce a more complete and
accurate report.” Id. at 39. The court also found it relevant that the defendant “had the
opportunity to depose [the expert] on his supplemental report and submit a rebuttal report.” Id.
As in Capitol Justice, the amendments at issue here were not changes to methodology,
but corrections to inputs into Dr. Rosenthal’s model—whether certain practices qualified for
inclusion in the control group and from what point in time the treatment effect of her model
should be calculated—and revisions to her calculations as a result.
Furthermore, the amendments are likely not so significant that exclusion of the updated
calculations would be warranted at trial. As discussed, although the First Circuit has upheld
exclusion of expert testimony where an expert’s opinion was not disclosed until a “final
addendum” to the expert’s report, it has not found that exclusion was warranted where an expert
makes more minor amendments to her report. See Martinez-Serrano, 568 F.3d at 282-83. And
the First Circuit has declined to require the exclusion of expert testimony even under more
extreme circumstances, such as where a defendant designated a new expert three months before
trial, following the death of its original expert, and defendant failed to serve a supplemental
expert report. See Ferrara & DiMercurio v. St. Paul Mercury Ins. Co., 240 F.3d 1, 10-11 (1st
Cir. 2001). It is thus unlikely that Dr. Rosenthal would be barred from referring to the updated
calculations at trial.
To be sure, the circumstances presented here are troubling. Dr. Rosenthal made two
substantial errors, and a third after she amended her report for the first time. The defense, not
relator’s counsel or Dr. Rosenthal herself, discovered her negligence. And instead of suffering
an adverse consequence, or such as exclusion of the amendments, she is being permitted to fix
the problems. Nonetheless, the Court concludes that the amendments should be considered
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supplemental disclosures covered by Rule 26(e). Furthermore, because relator provided the
amendments within several weeks of the deposition at which Dr. Rosenthal learned that there
were errors in her initial report, and in any event before the parties’ pretrial disclosures are due,
the Court finds that the report was supplemented “in a timely manner.” Fed. R. Civ. P.
26(e)(1)(A), (e)(2). As a result, the Court will not strike the amendments.
Nonetheless, there is obvious prejudice to defendant in terms of inconvenience and
expense, as well as potential prejudice in terms of disruption and delay. In fairness, therefore,
defendant should have an opportunity to cure any prejudice that will result from the
supplementation. That may include redeposing Dr. Rosenthal about the amendments; having an
opportunity to supplement defendant’s own expert reports to account for the changes to her
report; or undertaking any other measures that are reasonably calculated and proportionate to
cure any prejudice resulting from the amendments. In addition, of course, defendant will be
permitted to cross-examine her at the trial as to her lack of diligence.
Furthermore, because defendant is likely to incur additional expenses, such as attorney’s
fees and expert-witness fees, fairness dictates that those expenses should be borne by relator to
the extent they are reasonable under the circumstances. Other courts have similarly required a
party that supplements an expert report following the close of discovery to pay any costs borne
by the opposing party in responding to that supplement. See Evans v. Krook, 680 F. Supp. 3d
1080, 1109 (D. Minn. 2023); Richardson v. Korson, 905 F. Supp. 2d 193, 201 (D.D.C. 2012).
Relator must also, of course, ensure that the materials supporting Dr. Rosenthal’s amendments,
including the underlying data and code, have been provided to defendant.2
2 The Court does not have sufficient information before it to determine how the amendments to Dr.
Rosenthal’s report might impact the ongoing summary judgment briefing schedule. The Court is willing to entertain
proposals for modifications to the briefing schedule, including potentially allowing supplemental briefs, if either
party is able to demonstrate that they are necessary or appropriate.
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IV. 	Conclusion
For the foregoing reasons, defendant’s “Motion to Strike Supplemental Expert Report of
Dr. Meredith Rosenthal” (Dkt. No. 551) and defendant’s “Emergency Motion to Bar Relator
from Serving a Second Out-of-Time Expert Report and to Compel Relator to Seek Leave of
Court Prior to Expanding Court-Imposed Deadlines” (Dkt. No. 570) are hereby DENIED subject
to the conditions outlined in this order.
So Ordered.
/s/ F. Dennis Saylor IV
F. Dennis Saylor IV
Dated: March 16, 2026 	United States District Judge
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