CSG Law Alert: Northern District of California finds Prosecution Laches Applies to Patents Issued from Continuation Applications

In Sonos, Inc. v. Google LLC, No. C 20-06754 WHA (N.D. Cal. Oct. 06, 2023), the United States District Court for the Northern District of California held that a pair of Sonos patents that issued from related continuation applications were unenforceable under the doctrine of prosecution laches.

Sonos filed a provisional patent application in 2006 relating to managing groups of multimedia players. Sonos filed a corresponding non-provisional application in 2007 and then pursued claims of varying scope by filing a string of continuation applications over the next 10 years.

The Northern District held that, under the totality of the circumstances, two of the patents that issued from continuation applications were unenforceable under the doctrine of prosecution laches, which renders a patent unenforceable when it has issued after an unreasonable and unexplained delay in prosecution that constitutes an egregious misuse of the patent system.

The applications that ultimately issued as the unenforceable patents were filed 13 years after the filing of the original provisional application. However, the delay alone would not usually support a finding of laches, as this technique of keeping a pending patent application alive by filing a string of continuation applications is legally appropriate and often used by patent holders. There were other facts specific to this case that led the judge to find the patents unenforceable.

It appears that the claims of the unenforceable patents may have lacked clear support in the originally filed applications. Or, if there was support, the Court suggested that the invention as claimed in the unenforceable patents may not have been what the inventors considered the invention when they originally filed the provisional application. It was not until 13 years later, after Google had disclosed the invention to Sonos, that these claims were first presented to the patent office. The Court found that waiting 13 years to file these claims, after Google began selling products covered by the claims, was an egregious misuse of the statutory patent system to the prejudice of Google.

Although a finding of prosecution laches based solely on the legally appropriate and often-used practice of filing a string of continuation applications should be cause for concern, there were additional facts that led the Court to its holding in this case. It appears that the Court believed that Sonos’ actions in this case justified the finding of prosecution laches. Sonos has indicated that it will appeal, and we will continue to monitor this case. At this time, this case is cause for concern, but not panic.

If you would like to discuss the possible impact this case may have on your patent portfolio, or any other patent-related issues, please contact one of the authors of this alert.