The United States Court of Appeals for the Federal Circuit (“Federal Circuit”) recently issued an opinion in the case of Google LLC v. Sonos, Inc., Appeal No. 2024-1097 (August 28, 2025) (nonprecedential) regarding prosecution laches. The opinion did not address the delay in adding disclosure during prosecution; rather, it addressed whether there was prejudice.
Background
Sonos, Inc. (“Sonos”) appealed from a final judgment of the U.S. District Court for the Northern District of California holding certain claims of (1) U.S. Patent No. 10,496,966 (“the ’966 patent”) invalid and unenforceable, (2) claim 1 of U.S. Patent No. 10,848,885 (“the ’885 patent”) invalid and (3) certain claims of U.S. Patent No. 10,779,033 (“the ’033 patent”) invalid. The Federal Circuit reversed-in-part and affirmed-in-part the district court decision.
The Federal Circuit reviewed claim 1 of the ’885 patent which it called representative of the Zone Scene patents (the ’966 and the ’885 patents). In short, this claim recites the creation of “overlapping” zone scenes in which any given audio speaker can simultaneously belong to two different zone scenes. In August of 2019, during prosecution of the Zone Scene patents, Sonos amended the specification by adding a description of Fig. 5B where the user interface allows the user to create a zone scene from a list of all the available speakers. Sonos added the following description: “The list of zones in the user interface 520 includes ALL the zones in the system, including the zones that are already grouped.” The issue on appeal related to the disclosure of the overlapping nature of the zone scenes.
The Federal Circuit also addressed the validity of the ’033 patent (the Direct Control Patent) on different issues, but this post will not address those issues.
Early in the district court case Sonos moved for summary judgment of infringement of claim 1 of the ’885 patent. Google cross moved for summary judgment of noninfringement of that claim arguing inter alia that this claim could not be infringed because it lacked adequate written description of the overlapping zone scenes. The district court granted summary judgment of infringement to Sonos. The district court relied on the language added by Sonos during the prosecution history. Google then abandoned its written description challenge to the Zone Scene patents. A jury found the Zone Scene patents infringed claim 1 of the ’885 patent and none of the accused products infringed the asserted claims of the ’966 patent.
In a post-trial decision, the district court held the Zone Scene patents unenforceable due to prosecution laches. The district court held that Sonos was “guilty of unreasonable and inexcusable delay in its prosecution of” the Zone Scene patents because it did not claim the overlapping zone scenes until 13 years (April 2019) after the provisional, to which the Zone Scenes patent claimed priority, was filed. The court also found that Google was prejudiced because it began investing in the accused products at least by 2015 when it released its first products that practiced the invention. The district court dove deeper to look into whether the provisional application supported the Zone Scenes amendments, but ultimately found that the amendments were new matter and not supported by the initial disclosure. The district court then found that the asserted claims were anticipated by the accused products themselves.
The Federal Circuit notes that the district court addressed its invalidity determination of new matter based on 35 U.S.C. § 102 on the theory that “[t]hat which infringes later[,] anticipates before.” Since the district court found, on summary judgment, that the accused products infringed the ’885 patent, and the Zone Scene patents were not entitled to priority before 2019, the accused products therefore anticipated the claims of the ’885 patent. However, the court noted that the Zone Scenes patents were continuation-in-parts (“CIP”) of the priority application and, therefore, it addressed the new matter challenge through the lens of written description (adequate support). Since the Zone Scenes patents were CIPs, they did not receive priority to the provisional application, but to the application where the subject matter first appeared in the patent disclosures. Therefore, the Federal Circuit treated the matter as if it raised from § 112, not § 102. Ultimately, the court found that Google failed to establish a genuine dispute of material fact that the Zone Scene patents lack written description of the claimed overlapping zone scenes functionality.
The Federal Circuit instead of looking to the added disclosure describing Figure 5B, looked to the specification’s description of Figures 3A and 3B which showed that speakers could be formed into zones including speakers that were already in other zones. This description involves creating zones for different times of the day, e.g., morning. The court found that this disclosure was supported at least as early as 2007. Google argued that this is an alternative embodiment that does not have concurrent zones, but rather zones set for different times. The Federal Circuit disagreed.
Legal Analysis
The Federal Circuit noted that prosecution laches “may render a patent unenforceable when it has issued only after an unreasonable and unexplained delay in prosecution that constitutes an egregious misuse of the statutory patent system under the totality of the circumstances. Citing Cancer Rsch. Tech. Ltd. v. Barr Lab’ys, Inc., 625 F.3d 724, 728 (Fed. Cir. 2010). The court also noted that in defense, “Google must establish that Sonos’s delay in prosecution was unreasonable and inexcusable under the totality of circumstances, and that Google suffered prejudice attributable to that delay.” Citing Hyatt v. Hirshfeld, 998 F.3d 1347, 1362 (Fed. Cir. 2021).
Finding
The court limited its discussion to the prejudice element and determined that Google had not established prejudice. In its post-trial briefing, Google argued that it was prejudiced because it began investing in its products by at least 2015. However, the court noted that Google presented no evidence to support its assertion that its investment began in 2015 or that it was caught unaware of Sonos’ invention. The court also noted that an earlier application was published in 2013 before any of Google’s asserted investments. The court further noted that it is not improper to broaden claims during prosecution to encompass a competitor’s products if the disclosure supported the broadened claims. Citing Liebel-Flarsheim Co. v. Medrad, Inc., 358 F.3d 898, 909 (Fed. Cir. 2004). Because the court found that Google had not proven prejudice, the court did not address the delay in adding the new material and whether that would constitute prosecution laches.