Key Points:
- A genuinely new theory embedded in an expert report — rather than disclosed in contentions — risks being stricken.
- The District of New Jersey has not settled the question of whether Local Patent Rule 3.7 or the Pennypack factors govern exclusion, but courts may strike newly disclosed theories under either standard.
- Motions to strike expert reports are not a substitute for challenging allegedly vague infringement or invalidity contentions earlier in the case.
Motions to Strike
When does an expert report merely clarify a previously disclosed theory, and when does it cross the line into providing an impermissible new one?
In two January 2026 opinions in Jazz Pharmaceuticals v. Lupin, U.S. Magistrate Judge Jessica S. Allen largely declined to strike expert testimony, but drew a clear boundary: expert reports may flesh out existing theories, yet cannot be used to introduce a genuinely new invalidity theory that was never disclosed in formal contentions as required by the Local Patent Rules.
The rulings illustrate that there is a fine line between an expert permissibly specifying the application of a disclosed theory and impermissibly substituting “a new theory altogether.”
Courts must grapple with this question when faced with motions to strike expert reports. If a court determines a party has done the latter, it must decide whether the new theory must be stricken. But what standard applies when deciding if striking a new theory is appropriate? In the District of New Jersey, this remains an open question as judges have applied both a stricter standard under Local Patent Rule 3.7 as well as a more permissive standard under the so-called Pennypack factors.
The two opinions, dated January 15, 2026, resolved competing motions to strike expert reports. With one exception, the court declined to strike the theories. But the court did not determine the proper legal standard for exclusion. Rather, it held that under either standard, the theory should be excluded on the facts of the case.
Local Patent Rule 3.7
In the District of New Jersey, parties’ invalidity and infringement theories must be set forth early in the case through exchanges of formal contentions. It is undisputed that Local Patent Rule 3.7 governs amending these contentions and that new theories should not be embedded within expert reports. Rather, a party can amend its contentions only by order of the court upon a timely application and showing of good cause.
Thus, in each opinion, the court first assessed whether the expert reports contained impermissible new theories. Regarding the infringement report, the court found that no new theories were disclosed and also observed that “Defendants’ current motion to strike an expert report could easily be confused with a motion challenging the specificity of an infringement contention.” ECF No. 266 at 12. Thus, finding that no new theories were disclosed and there was nothing to consider striking, in this opinion, the court did not reach a determination of the proper standard for exclusion.
Regarding the invalidity reports, the court assessed five substantive objections, determining that four did not contain any new theories but merely permissible use of prior art references for background discussion, motivation to combine, and further specification of a disclosed theory. However, the court concluded that a fifth theory, “a new sodium reduction theory supported by the references to Azizi and Dunbar” (ECF No. 256 at 16), was not properly disclosed in the invalidity contentions.
So finding, the court rejected defendants’ argument that the references, which were not cited in the invalidity contentions, were “cited as supplemental motivations to combine or as complimentary proof in support of a previously disclosed theory.” Id. at 16. Accordingly, the court next assessed whether to strike the new theory. The court explained that under the more stringent LPR 3.7 standard, noncompliance and use of a new theory “would independently warrant striking the new theory.” Id. at 18.
The Pennypack Factors
The Court further found that even under the more liberal Pennypack factors, striking would still be warranted. The Pennypack factors for analyzing a request to exclude expert testimony were set forth by the Third Circuit in Meyers v. Pennypack Woods Home Ownership Ass’n, 559 F.2d 894, 904-05 (3d Cir. 1977):
(1) “the prejudice or surprise in fact of the party against whom the excluded witnesses would have testified” or the excluded evidence would have been offered;
(2) “the ability of that party to cure the prejudice”;
(3) the extent to which allowing such witnesses or evidence would “disrupt the orderly and efficient trial of the case or of other cases in the court”;
(4) any “bad faith or willfulness in failing to comply with the court's order”; and
(5) the importance of the excluded evidence.
The court reviewed the Third Circuit’s Pennypack factors and found that in addition to the first, second and third factors, the fifth and most important factor weighed in favor of exclusion. In particular, the court observed that defendants had several additional invalidity theories they could still pursue and that Defendants’ failure to address this factor suggested the invalidity theory was not critical.
These two orders serve as a potent reminder that infringement and invalidity theories must be properly disclosed pursuant to the DNJ’s Local Patent Rules (relatively early in litigation proceedings compared to other districts), and that, under either Local Patent Rule 3.7 or Pennypack, new theories outside the bounds of these contention disclosures may be struck.
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