Mirror Worlds Technologies, LLC (“Mirror Worlds”) sued Meta Platforms, Inc. (“Meta”)—formerly Facebook, Inc.—in the Southern District of New York for patent infringement. The lawsuit involved three patents related to storing, organizing, and presenting data in time-ordered streams. These patents purportedly introduced a unique method for automatically storing documents in chronological order with timestamps. Mirror Worlds accused several Facebook features, including the News Feed, Timeline, and Activity Log, of infringing these patents.

During claim construction, the parties agreed that the term “main stream” (1) included every data unit received or generated by the computer system and (2) must be a time-ordered sequence of data units. The terms “main stream” and “main collection” were treated as equivalent, as each claim contained one of these terms.

Summary Judgment of Non-Infringement

Following fact and expert discovery, Meta moved for summary judgment on multiple grounds, including non-infringement. The district court granted Meta’s motion, concluding that Mirror Worlds’ expert testimony lacked sufficient evidentiary support to allow a reasonable jury to find infringement.

Meta argued that its accused systems (News Feed, Timeline, and Activity Log) did not meet the “main stream” or “main collection” limitations, which required storing every data unit received. Meta provided evidence that, while its systems received data, they did not store all of it in the accused “main streams” or “main collections.” To simplify, Meta’s systems processed incoming data streams but did not retain all of the data received.

Additionally, for two of the three asserted patents, the claims required a “glance view”—a feature where a user hovering over a document link receives an indication of its content. Meta argued that its accused links merely served as source identifiers and did not provide insight into the document’s content as required by the claims.

Federal Circuit Appeal

On appeal, Mirror Worlds contended that genuine issues of material fact existed, relying heavily on its technical expert. However, the Federal Circuit rejected these arguments, affirming the district court’s decision.

Regarding the “glance view” limitation, Mirror Worlds’ expert made representations about Facebook’s source code without submitting the code to the court. In contrast, Meta’s expert presented authenticated screenshots demonstrating that the accused links displayed only source information—not content from the linked documents. The court found Meta’s evidence to be uncontested proof of non-infringement.

For the “main stream” limitation, Meta identified specific data (e.g., coefficient data) that was received by the accused system but not stored, contradicting Mirror Worlds’ claims. While both parties agreed that the accused system received coefficient data, Mirror Worlds argued that all information used by the system was stored. The Federal Circuit disagreed, noting that Mirror Worlds’ evidence showed only that some data was stored, not all.

Meta, in contrast, provided firsthand witness testimony confirming that its systems did not store coefficient data. The court disregarded Mirror Worlds’ expert opinion as conclusory and unsupported, especially since he failed to explain why his analysis ignored relevant source code evidence indicating that the accused system did not store all received data.

Key Takeaways for Litigators

This case highlights critical considerations when preparing expert testimony in patent litigation, particularly at the summary judgment stage. Here are some practical takeaways:

1. Thoroughly examine the factual record – Ensure that your expert has access to a complete and well-supported factual foundation for their opinion.
2. Tie expert testimony to claim construction – Expert opinions should be aligned with the court’s claim construction rulings and demonstrate how the facts support your client’s position.
3. Address all rebuttal points – Your expert should directly refute opposing arguments and counter-examples raised by the adversary.
4. Use reliable, authenticated evidence – Ensure that any evidence relied upon by your expert is verifiable and admissible, avoiding reliance on unauthenticated or incomplete materials such as undated screenshots.

This decision reinforces the importance of competent and reliable expert testimony, particularly in patent cases where technical details can make or break infringement claims. Ensuring that expert opinions are well-supported and based on admissible evidence is critical to surviving summary judgment and prevailing at trial.

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