Google v. Sonos: Federal Circuit Validates Strategic Patent Continuation Practice (With Limits)

Patent

by Dennis Crouch

The Federal Circuit has now wiped away Judge William Alsup’s dramatic post-trial decision in Sonos v. Google. In a nonprecedential opinion, the court reversed the lower court’s finding of prosecution laches, reiterating that laches is an equitable defense reserved for rare cases. Google LLC v. Sonos, Inc., No. 2024-1097 (Fed. Cir. Aug. 28, 2025).

Prosecution laches requires both (1) an unreasonable and unexplained delay in patent prosecution and (2) a showing of prejudice to the accused infringer in the form of intervening rights (e.g. evidence that others “invested in, worked on, or used the claimed technology during the period of delay”). Here, Google failed to present evidence that it (or others) changed their position or made investments in reliance on Sonos’s delay and so laches could not apply. At times, egregious delay can trigger laches absent a specific showing of harm. Here, however, the panel emphasized that standard continuation practice, even over more than a decade, is not itself an “egregious misuse” of the system sufficient to trigger laches in the absence of specific prejudice. Prior prosecution laches cases all involved pre-1995 patents and decades of delay and this was the first time prosecution laches had been used to render a post-1995 patent unenforceable in a situation where delays in prosecution automatically delayed patent term as well. The court ultimately reversed Judge Alsup’s unenforceability ruling and reinstated the jury’s $32 million verdict on the Sonos “zone scenes” patents.

Although Sonos won the appeal, the decision does not provide a full green light to the continuation practice found here – particularly where claims covering competitor activity are first added to the patent family long after the original filing and publication dates. The Federal Circuit’s analysis focused heavily on the fact that Sonos’s 2007 patent application previously published, well before Google’s alleged investments began in 2014-2015. This meant Google could not claim prejudice from incorporating into its products a feature that was already publicly disclosed in a pending patent family.

However, the decision leaves open questions about prosecution laches in cases where the accused infringer can demonstrate concrete reliance interests that developed during periods of prosecution delay. Patent prosecutors should note that while this case validates continuation practice within reasonable bounds, it may prompt a reconsideration of continuation strategies that extend well beyond a decade – and at least warrants a discussion with clients regarding that third or fourth continuation filing.

The appellate court also addressed the district court’s highly unusual handling of Google’s written description defense. During trial, the district court began questioning its own prior summary judgment ruling that had rejected Google’s written description challenge to the “overlapping zone scenes” claims. The court ordered additional briefing and ultimately concluded that Sonos’s claims were invalid under 35 U.S.C. § 112(a) for lack of written description. The theory was that Sonos had added new matter in its 2019 continuation application specification to support the new claims targeting Google’s multi-zone speaker products. Although Sonos had added a few lines to Figure 5B’s description, the Federal Circuit concluded that Sonos’s original patent filings from 2006–2007 adequately disclosed the “overlapping zone scenes” feature—at least sufficiently to avoid a directed verdict. The court found dispositive disclosure in the specification’s description of “Morning” and “Evening” scenes, where the same rooms (Bedroom, Den, and Dining Room) appeared in both scenes, plainly providing adequate written description for overlapping zone scenes. On remand, the district court is instructed to consider any remaining motions that were mooted by its original judgment, though the core infringement finding and damages award should now stand.

The court did not fully explain its reasoning but noted some doctrinal importance attached to the fact that the new text was added in a continuation rather than a continuation-in-part (CIP) (or directly from a provisional).  However, the court also noted that the issue is likely “a distinction without a difference.”

  • With a CIP, if the new claims are not supported by the original filing, the result is not direct invalidity but instead just a loss of that priority claim.  But, in most cases, the later filing date will result in invalidity based upon intervening prior art.
  • With a continuation, the later application is supposed to be the same disclosure without any new matter. As such, if the claims are not supported then the result is invalidity for lack of written description.

Here, the appellate panel explained:

The [district] court characterized its invalidity determination based on the asserted new matter as one arising under 35 U.S.C. § 102 . . . However, because the Zone Scene patents are continuation applications of the priority application—not continuations-in-part (“CIPs”)—we will address the new matter challenge through the lens of written description. . . . Although this may be a distinction without a difference, for clarity of this opinion we treat the district court’s judgment as one arising under § 112, not § 102.

While the court’s analysis here may be inconsequential for this particular case, it highlights a potential issue with many inter partes review proceedings where the petitioner challenges the patent based upon the combined 112/102 theory.  This case suggests that if those are continuation patents then the theory should be straight 112 and thus fail to comply with the limitation that IPRs can only rely upon 102/103 grounds.

Back to Sonos: I am troubled that the Federal Circuit released this opinion in nonprecedential status. I expect this designation resulted from the unusual procedural posture – particularly the district court’s sua sponte post-trial summary judgment ruling under Federal Rule of Civil Procedure 56(f), revised pursuant to Rule 54(b). The Federal Circuit had to navigate the irregularity of a court essentially granting summary judgment on an issue that Google had never properly moved for and that had not been tried to a jury. While the court acknowledged that district courts possess authority to make such rulings with proper notice, it noted that “this case exemplified why such sua sponte invalidity judgments are disfavored.” See, e.g., Astellas Pharma, Inc. v. Sandoz, Inc., 905 F.3d 1346 (Fed. Cir. 2018) (reversing district court’s sua sponte § 101 invalidation). Despite these procedural complexities warranting careful analysis, the substantive holdings on prosecution laches and written description deserve precedential weight, particularly given the relative scarcity of prosecution laches cases in the modern patent system.

The only aspect of Judge Alsup’s judgment that survived appellate review was his pre-trial ruling that Sonos’s separate “Direct Control” patent claim was invalid as obvious.  The Federal Circuit affirmed this portion of the judgment without much fanfare. The panel found no error in the obviousness analysis, concluding that Sonos had not identified any genuine factual dispute to preclude summary judgment on the Direct Control claim. The court agreed that Google’s YouTube Remote (YTR2), in view of Google’s own U.S. Patent 9,490,998, would have rendered obvious the asserted claims relating to transferring playback responsibility from a computing device to a speaker through a mobile app interface. Thus, that patent claim remains invalid for obviousness. Truthfully it is hard for me believe that I am playing down this ruling as a minor part of the case.  Summary judgment of obviousness was once quite rare, but it has become increasingly common in our post-AIA world as courts have grown more comfortable resolving obviousness questions as matters of law.

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