Revisiting Judge Alsup's 2023 Post-Trial Criticism of Sonos's Continuation Practice
The CAFC win sinks the "submarine patent" characterization
The Federal Circuit’s recent reversal of Judge William H. Alsup’s prosecution laches finding in the Google v. Sonos patent dispute provides a compelling occasion to revisit the district court’s sharp critique of modern continuation practice. In his October 2023 opinion, Judge Alsup characterized Sonos’s patent strategy not just as improper, but as a subversion of the patent system’s purpose.
While the Federal Circuit ultimately found Judge Alsup’s legal conclusion on laches to be unsupported by the evidence, the contrast between the two opinions highlights a fundamental tension between the perceived fairness of a patentee’s conduct and the specific legal standards required to render a patent unenforceable.
The District Court’s View: An “Egregious Misuse” of the System
Judge Alsup’s post-trial opinion was unequivocal in its condemnation of Sonos’s strategy.
National headlines about the case highlighted this criticism, saying: “Judge blasts Sonos for abusing patent system and throws out $32.5 million win against Google” and “Judge Axes Sonos' $33M Win, Calling Suit 'Sad' And 'Wrong.'”
Indeed, the senior United States district judge of the U.S. District Court for the Northern District of California framed the case as one where the supposed inventor was not an industry leader, but a follower lying in wait. His October 2023 opinion stated:
This was not a case of an inventor leading the industry to something new. This was a case of the industry leading with something new and, only then, an inventor coming out of the woodwork to say that he had come up with the idea first — wringing fresh claims to read on a competitor's products from an ancient application (Post-Trial Decision, p. 2).
The core of Judge Alsup’s criticism was the thirteen-year gap between Sonos’s 2006 priority filing and its 2019 assertion of claims covering “overlapping zone scenes”—a feature Google had already disclosed to Sonos in 2014 and launched in products by 2015. The judge saw this delay as a deliberate manipulation intended to ensnare an established market.
The district court concluded that the patent system, which is “intended to promote and protect innovation,” was instead “used to punish an innovator and to enrich a pretender by delay and sleight of hand” (Post-Trial Decision, p. 55).
On the legal question of prosecution laches, Judge Alsup found both required elements were met:
Unreasonable Delay: The thirteen-year delay was deemed unreasonable and inexcusable, with the judge noting that Sonos “never provided any sworn explanation for why it waited until April 2019 to claim overlapping zone scenes” (Post-Trial Decision, p. 30).
Prejudice: Prejudice was found because Google had established intervening rights. The decision states, “There is no question that Google worked on, invested in, and used the claimed technology during the period of Sonos's delay,” starting with its first accused products in 2015 (Post-Trial Decision, p. 32).
For Judge Alsup, Sonos’s actions were a clear abuse. “It is wrong that our patent system was used in this way,” he wrote, concluding that Sonos engaged in a “designed delay” to make its patent monopoly “square with the period when the commercial profit from it would be highest” (Post-Trial Decision, p. 35).
The Federal Circuit’s Reversal: A Focus on Evidence and Disclosure
The Federal Circuit, in its non-precedential opinion, took a different path. It sidestepped the district court’s broad criticisms about the fairness of continuation practice and focused exclusively on whether Google had met its legal burden to prove prejudice. The reversal was based on two key failures in Google’s argument.
First, the court found a lack of concrete evidence. It concluded that Google “presented no evidence—testimony or otherwise—to support its assertion that its investment in those products actually began in 2015” (Fed. Cir. Op., p. 16). This evidentiary gap was fatal to a finding of prejudice, which cannot be presumed.
Second, the Federal Circuit held that even if Google’s 2015 investment timeline was accepted, the laches defense would fail as a matter of law. The 2007 Sonos application—which the court found did disclose the overlapping zone scene invention—was published when it issued as a patent in July 2013, well before Google’s asserted investment period began. This public disclosure was dispositive.
The court stated, “Google cannot be prejudiced by incorporating into its products a feature that was publicly disclosed in a patent application prior to its investment” (Fed. Cir. Op., p. 16).
This reasoning directly counters the narrative of a “submarine patent” catching an unsuspecting industry off guard (Post-Trial Decision, p. 34). The invention, in the Federal Circuit’s view, was not lurking in secret; it was available to the public (Fed. Cir. Op., p. 16).
Furthermore, the Federal Circuit implicitly endorsed the continuation strategy that Judge Alsup had criticized so heavily. While Judge Alsup saw Sonos “wringing fresh claims” to target a competitor (Post-Trial Decision, p. 2), the appellate panel cited precedent confirming that “it is not improper for an applicant to broaden his claims during prosecution in order to encompass a competitor's products, as long as the disclosure supports the broadened claims” (Fed. Cir. Op., p. 16 (quoting Liebel-Flarsheim Co. v. Medrad, Inc., 358 F.3d 898, 909 (Fed. Cir. 2004)).
In the end, Google failed to present any evidence that it suffered prejudice attributable to Sonos’s alleged delay the Federal Circuit held that the district court abused its discretion in holding the Zone Scene patents unenforceable for prosecution laches.
A Permissible Strategy, Even if Criticized
The divergence between these two opinions is instructive for IP professionals. Judge Alsup’s decision voices a frustration shared by many tech companies who find themselves targeted by patents emerging from seemingly long-dormant application families.
However, the Federal Circuit’s reversal reinforces that prosecution laches is a high bar to clear. An accused infringer must do more than point to a long delay; it must prove it was prejudiced by a lack of notice.
The panel cited Eli Lilly & Co. v. Hospira, Inc., 933 F.3d 1320, 1334 (Fed. Cir. 2019), reiterating that, although 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” (Fed. Cir. Op., p. 16).
As this case makes clear, the publication of a patent application containing the key disclosure can effectively neutralize a laches defense, even if specific claims covering that disclosure are not pursued for many years. Determining the date and sufficiency of that disclosure is often easier said than done.
Judge Alsup himself acknowledged continuation practice's legitimacy in certain settings, stating, "It is also true that a patent applicant is allowed to draft claims to read on competitors’ products and claim a priority date that precedes them... [b]ut that is only so long as there is no unreasonable, inexcusable delay, and so long, of course, that an earlier specification really did disclose the claimed invention." (Post-Trial Decision, p. 32, citing Liebel-Flarsheim Co. v. Medrad, Inc. (citing Kingsdown Med. Consultants, Ltd. v. Hollister Inc., 863 F.2d 867, 874 (Fed. Cir. 1988)). The district court, however, found Sonos failed both of his conditions, concluding the thirteen-year gap was an inexcusable delay and the original specification never actually disclosed the overlapping feature.
In direct contrast, yet citing the same precedent in Liebel-Flarsheim Co., the Federal Circuit determined the second condition was met, finding the core invention was publicly disclosed when the parent application issued as a patent in 2013 (Fed. Cir. Op., p. 16). Because the 2013 publication—deemed by the panel to have sufficient written description—put the public on notice prior to Google's investment, the Federal Circuit held that Google could not have suffered the legal prejudice required for a laches defense, thereby validating the very practice Judge Alsup had condemned.
Ultimately, what one judge saw as a “sleight of hand” (Post-Trial Decision, p. 55), the appellate court viewed as a legally permissible, if aggressive, use of the continuation process.
Disclaimer: This is provided for informational purposes only and does not constitute legal or financial advice. To the extent there are any opinions in this article, they are the author’s alone and do not represent the beliefs of his firm or clients. The strategies expressed are purely speculation based on publicly available information. The information expressed is subject to change at any time and should be checked for completeness, accuracy and current applicability. For advice, consult a suitably licensed attorney and/or patent professional.