Key Points

• DNJ court denies motion to compel inventor and prosecuting attorney depositions during claim construction discovery for failure to comply with Local Patent Rule 4.3(b) JCCPS witness disclosure requirements.
• Vague reference to "inventor depositions" in LPR 4.2 disclosures does not satisfy Rule 4.3(b) witness identification and testimony summary requirements.
• Incomplete claim construction disclosures risk preclusion of extrinsic evidence at Markman hearing in District of New Jersey patent cases.

In patent litigation in the District of New Jersey, parties must make specific, complete witness disclosures in their claim construction filings or risk preclusion of that evidence at the Markman stage.

That’s the overarching lesson to be drawn from a recent decision by U.S. Magistrate Judge Elizabeth A. Pascal that denied a defendant's motion to compel inventor and prosecuting attorney depositions during claim construction discovery.

The Court found that the defendant's failure to identify the witnesses in the Joint Claim Construction and Prehearing Statement (JCCPS) as required by Local Patent Rule 4.3(b) was, standing alone, likely a sufficient basis for denial.

DNJ’s Local Patent Rules

The DNJ Local Patent Rules contain requirements for various exchanges of information in discovery, such as contentions for infringement and invalidity and disclosure of claim terms and evidence during claim construction. These Local Patent Rules are in place to further the goal of full, timely discovery and provide adequate notice of the parties’ positions.

These requirements are not to be taken lightly, and the DNJ does not hesitate to strictly enforce them. See our prior alerts, Court Rejects Amendment to Add Indefiniteness Theories Based on Plain Language of Patent and In Patent Dispute, NJ Federal Court Declines to Clarify Standard for Striking Expert Theories.

Magistrate Judge Pascal’s ruling denied a defendant’s motion to compel depositions of the patent inventor and prosecuting attorney during claim construction discovery because the defendant violated Local Patent Rule 4.3(b) by failing to identify the proposed witnesses in the parties’ JCCPS.

Rules Relating to Claim Construction

DNJ Local Patent Rule 4.1 requires the parties to first exchange “a list of claim terms which that party contends should be construed by the Court.” LPR 4.2 then requires an exchange of preliminary claim constructions for those terms and intrinsic and extrinsic evidence, including “testimony of all witnesses including expert witnesses.” LPR 4.2 also specifies that “[w]ith respect to all witnesses including experts, the identifying party shall also provide a description of the substance of that witness' proposed testimony that includes a listing of any opinions to be rendered in connection with claim construction.”

Finally, LPR 4.3 requires a joint claim construction and prehearing statement containing information from these exchanges to be filed. As relevant to the decision, LPR 4.3(e) requires that the JCCPS include “[w]hether any party proposes to call one or more witnesses at the Claim Construction Hearing, the identity of each such witness, and for each witness, a summary of his or her testimony . . . .” LPR 4.3(f) cautions that “[a]ny evidence that is not identified” in the parties’ exchanges under LPR 4.2 described above “shall not be included” in the JCCPS.

Hardware Patent Dispute

Plaintiff Assa Abloy Fenestration, LLC sued Vision Industries Group, Inc. for patent infringement involving a window hardware patent. Pursuant to the operative scheduling orders, the parties were required to identify all intrinsic and extrinsic evidence to oppose the other party’s claim constructions by May 5, 2026 and submit a JCCPS by May 27, 2026.

On June 5, 2026, after the JCCPS had already been filed, the defendant requested that the plaintiff make available two witnesses for deposition during the claim construction discovery period, which was set to close two weeks later on June 19 — the named inventor and the prosecuting attorney for the patent-in-suit. Plaintiff objected on three grounds: (1) defendant’s failure to disclose the witnesses in the JCCPS as required by Local Patent Rule 4.3(b); (2) lack of relevance to claim construction; and (3) prejudice from having to prepare witnesses on an expedited basis. Notably, plaintiff did not object to producing these witnesses during ordinary fact discovery following the Markman hearing.

Four Reasons for Denial

The Court observed that the Local Patent Rules do not specify the remedy to be applied for a violation of Local Patent Rule 4. The Court noted that DNJ judges “frequently exercise their discretion and consider whether the non-offending party would be prejudiced if the Court allowed the evidence to remain in the record.”

The Court concluded that multiple reasons supported denying the motion to compel.

First, the Court found that defendant failed to properly identify the witnesses in the JCCPS, as mandated by the Rule. The Court found that defendant’s reference to its potential reliance on evidence such as “technical documents, design document[s], emails and inventor depositions” in its LPR 4.2 disclosures did not satisfy the specific identification and testimony-summary requirements of Rule 4.3(b). The Court rejected defendant’s argument that it could not comply without first taking the depositions, noting that “counsel routinely summarize a witness’s expected testimony before that testimony is taken.” Accepting defendant’s argument would “substantially undermine” the Rule’s disclosure requirement.

Second, the Court found defendant failed to articulate why the testimony would be relevant to claim construction, noting that testimony about “how a person of ordinary skill in the art would understand the claim terms,” was precisely the type of opinion to be offered by experts, not fact witnesses. The Court further observed that extrinsic evidence is of less value for claim construction than intrinsic evidence, such as the claims, written description, and prosecution history.

Third, the Court concluded that compelling the depositions near the close of claim construction would likely prejudice plaintiff “by forcing it to prepare these witnesses on an expedited basis for what may be irrelevant testimony.” The Court found this prejudice outweighed any benefit to defendant.

Fourth, the Court found no concrete prejudice to defendant by delaying the depositions until after the Markman hearing during normal discovery. In particular, the Court observed defendant was not “entitled” to lock down testimony, and there was no showing that the testimony would be relevant to claim construction.

Thus, the Court denied the motion to compel the depositions prior to the Markman hearing and further stated that nothing in the Court’s order shall preclude defendant from taking the depositions after the Markman hearing subject to the Scheduling Order and Federal Rules of Civil Procedure.

On August 3, 2026, defendant filed an appeal of Magistrate Pascal’s decision to the presiding District Judge.

Paul W. Kalish and Jonathan J. Madara are members of the IP Litigation team in Fox Rothschild’s Princeton, NJ office and write about patent litigation decisions in the District of New Jersey. Contact Paul at pkalish@foxrothschild.com or 609.895.6751 and Jonathan at jmadara@foxrothschild.com or 609.844.7428.

This information is intended to inform firm clients and friends about legal developments, including the decisions of courts and administrative bodies. Nothing in this alert should be construed as legal advice or a legal opinion. Readers should not act upon the information contained in this alert without seeking the advice of legal counsel. Views expressed are those of the authors and not necessarily this law firm or its clients.