/>iThe Federal Circuit’s recent decision in Google LLC v. Sonos, Inc. (24-1097) offers a compelling look at the evolving doctrine of prosecution laches, the written description requirement, and the practical realities of patent enforcement in the tech sector where technology typically evolves much faster than other industries. The case, which pitted two giants of the smart speaker and media playback industry against each other, involved a lengthy prosecution resulting in claims that covered technology adopted by Google before issuance that, according to the appellate panel, did not rise to the level of egregious misuse required for a patent to be rendered unenforceable under the doctrine of prosecution laches.
Background: The Zone Scene and Direct Control Patents
Sonos’ asserted patents, the so-called “Zone Scene” patents (U.S. Patent Nos. 10,469,966 and 10,848,885) and the “Direct Control” patent (U.S. Patent No. 10,779,033), are directed to the orchestration of media playback across multiple devices. The Zone Scene patents describe and claim the ability to create and save overlapping groups of speakers — “zone scenes” — to play synchronized audio, while the Direct Control patent covers the use of a control device (like a smartphone) to transfer playback responsibility to a speaker.
The litigation began with Google seeking a declaratory judgment of noninfringement in the Northern District of California, followed by Sonos’ infringement suit in the Western District of Texas. After a different panel of the Federal Circuit chastised the Western District of Texas for trying to hang on to the dispute, the cases were consolidated in the Northern District of California.
A series of summary judgment motions and a jury trial set the stage for the second appellate review. In this aspect, before trial, the district court found that the Direct Control patent was invalid as obvious over Google’s YouTube Remote system in combination with Google’s U.S. Patent No. U.S. Patent 9,490,998. As a result, only the Zone Scene patents were at issue at trial and factored into the more than $32.5 million damages verdict awarded to Sonos by the jury.
On appeal, Sonos’ attempts to persuade the Federal Circuit that the district court was wrong about the invalidity of the Direct Control patent were unsuccessful. In fact, this was the only issue on appeal in which the Federal Circuit agreed with the district court. The other two challenges on appeal are discussed in a bit more detail below.
Written Description: Sounds Clear Enough
A central issue on appeal was whether Sonos’ Zone Scene patents were supported by adequate written description, particularly regarding the “overlapping” nature of zone scenes — where a single speaker could belong to multiple groups. The district court initially sided with Sonos on this issue but reversed course post-trial holding that the Zone Scene patents lacked written description for this feature and were thus invalid under 35 U.S.C. § 102. Wait, why § 102 you might ask? Well, the district court reasoned that, because Sonos’ 2019 amendment to the specification — which “clarified” the overlapping functionality — was a new matter not supported by the original 2006 and 2007 applications, the earliest filing date afforded the claims was after Google’s accused products were introduced and the claims were anticipated under § 102 by Google’s accused products.
The Federal Circuit disagreed with this approach by the district court procedurally and substantively. It thus treated the lower court’s invalidity ruling as arising under 35 U.S.C. § 112 —not 35 U.S.C. § 102 — and found that the original disclosure, particularly the descriptions accompanying Figures 3A and 3B, adequately conveyed to a person of ordinary skill that the inventors possessed the concept of overlapping zone scenes as early as 2007. The court emphasized that the written description requirement under 35 U.S.C. § 112 is satisfied if the disclosure, as a whole, reasonably conveys possession of the claimed invention. Here, the specification discussed multiple groups and scenes with overlapping room assignments, which was considered sufficiently descriptive of the overlapping nature of zone scenes. As such, the appellate panel reversed the district court’s invalidity judgment on this “ground.”
Prosecution Laches: Delay Does Not Make a Modern Submarine!
The other key issue on appeal was whether the Zone Scene patents were unenforceable under the doctrine of prosecution laches. After trial, the district court held the Zone Scene patents to be unenforceable under the doctrine of prosecution laches, finding that Sonos’ 13-year delay in claiming overlapping zone scenes was an “egregious misuse” of the patent system. In its reversal of the lower court’s ruling, the appellate panel drew heavily from the guidance in Hyatt v. Hirshfield where it is explained that prosecution laches may render a patent unenforceable where a patentee’s conduct constitutes an egregious misuse of the statutory patent system and set forth the two required elements:
- The patentee’s delay in prosecution must be unreasonable and inexcusable under the totality of circumstances; and
- The accused infringer must have suffered prejudice attributable to the delay.
The panel found that Google had not suffered the requisite prejudice under the second prong and reversed the district court’s laches ruling. While the delay in claiming overlapping zone scenes by Sonos is certainly lengthy, the fact that the disclosure supporting the technology was published in 2013 — well before any purported investment by Google into the technology — weighed against any argument by Google that it had been caught unaware or that it invested in the technology in reliance on the absence of such claims. In this vein, the opinion includes a reminder that a patentee is free to pursue claims in a continuation application that encompass a competitor’s products as long as there is supporting disclosure. In fact, while “subject matter disclosed but not claimed is generally dedicated to the public, there is an exception for subject matter ‘claimed in a continuation or other application.’”
This fact pattern is easily distinguishable from the fact pattern in PMC v. Apple where PMC had filed hundreds of continuation applications, delayed prosecution for decades, and only surfaced its claims once the technology was widely adopted — classic submarine tactics. PMC’s calculated approach to keeping its claims underwater until after the technology was widely adopted was viewed by the Federal Circuit to be highly prejudicial to Apple because Apple had begun developing its technology in early 2000 and started to offer it commercially in 2003 — a decade before the asserted patent was issued. Indeed, there was no publication of the patent application prior to issuance as was the case here with the Zone Scene patents.
The “long con” strategies that once defined the era of submarine patents — strategies that were at the heart of the PMC v. Apple saga — simply did not exist here. This case demonstrates that mere delay, without concrete prejudice to competitors, is insufficient to trigger prosecution laches. The Federal Circuit’s insistence on actual prejudice, not just theoretical harm, marks a significant check on the reach of the prosecution laches doctrine.
Takeaways for Patent Prosecution and Enforcement
The opinion underscores several key lessons:
- Written Description Still Matters – Even in complex, evolving technologies, the original disclosure must support later-claimed features. However, courts will read the specification as a whole and give credit where the invention is reasonably described.
- Prosecution Laches Requires Prejudice – The doctrine is alive but slightly more cabined than before. Without evidence that a competitor invested in the technology before the claimed technology was disclosed, laches will not bar enforcement.
- Strategic Prosecution Must Be Balanced – While continuation practice and claim amendments are legitimate, unreasonable and unexplained delays that prejudice others remain risky.
This decision puts serious limits on defendants who may want to invoke laches based on continuation applications – especially where they argue that the patent owner could have filed the claims earlier. While the failure to assert a claim in a timely manner can result in that claim being barred by laches under certain facts, prosecution delay alone is not enough to prevent a claim from being enforceable: It is up to the defendant to prove why that delay makes it unfair for the court to give relief, including a showing of prejudice by the accused infringer. In this aspect, this decision is helpful for patent owners to rely on when arguing a lack of prejudice to the accused infringer (providing that the later claimed technology was publicly available before the accused infringer started to develop and/or commercialize the technology).
In addition, this decision is a valuable reminder to companies and their respective patent counsel when performing clearance analyses to not just review issued claims in a patent family, but also consider the specification and other non-claimed technology if the family remains open.
