The US Court of Appeals for the Fourth Circuit affirmed a district court’s exclusion of damages evidence under Federal Rule of Civil Procedure 37(c)(1) and the resulting grant of summary judgment against the plaintiff on all claims. Deque Sys. Inc. v. BrowserStack, Inc., Case No. 25-1534 (4th Cir. June 5, 2026) (Agee, Traxler, Floyd, JJ.)

Deque Systems develops software that helps businesses make websites accessible to users who have visual and hearing impairments. Deque sued competitor BrowserStack for copyright infringement, false advertising, breach of contract, and unjust enrichment, alleging that BrowserStack reverse-engineered Deque’s software to develop a competing product and falsely advertised it as “5x faster” than Deque’s flagship offering.

Under the district court’s scheduling order, initial disclosures were due on June 7, 2024; expert disclosures were due on August 9, 2024; and fact discovery closed on October 11, 2024. Although Deque timely served its Rule 26(a)(1) initial disclosures, it failed to provide a computation of damages as required by Rule 26(a)(1)(A)(iii). When BrowserStack later served an interrogatory seeking the categories and calculations of Deque’s claimed damages, Deque again declined to provide a damages computation, stating only that it intended to seek all available damages and that its calculations remained incomplete.

Deque also failed to serve a damages expert report by the August 2024 expert disclosure deadline. After retaining new counsel, Deque disclosed a $30 million damages calculation on October 8, 2024, just three days before the close of discovery. BrowserStack moved to exclude the damages evidence and sought summary judgment.

The district court excluded Deque’s damages evidence under Rule 37(c)(1), finding that Deque failed to comply with Rule 26’s disclosure requirements. Because Deque could no longer prove damages and failed to establish entitlement to injunctive relief, the district court granted summary judgment in BrowserStack’s favor on all claims. Deque appealed.

The Fourth Circuit affirmed. The Court explained that Rule 37(c)(1) “gives teeth” to Rule 26’s disclosure requirements by prohibiting a party from using information that was not properly disclosed during discovery. The Court found that Deque had “indisputably failed to comply” with Rule 26(a)’s damages disclosure requirements by failing to provide a damages computation in its initial disclosures, expert disclosures, or interrogatory responses. The Court rejected Deque’s argument that its disclosure of damages in a rebuttal expert report three days before the close of discovery constituted a timely disclosure.

Turning to the propriety of the sanction, the Fourth Circuit applied the five-factor test set forth in its 2003 Southern States Rack & Fixture, Inc. v. Sherwin-Williams Co. decision:

• Surprise to the opposing party
• Ability to cure the surprise
• Disruption of trial
• Importance of the evidence
• Explanation for the nondisclosure

The Fourth Circuit concluded that all five factors favored exclusion. BrowserStack was plainly surprised by Deque’s $30 million damages claim, which was disclosed only days before discovery closed. Curing that surprise would have required reopening discovery and significantly delaying the proceedings. Although the damages evidence was important, Deque failed to offer any meaningful justification for its repeated failure [...]

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