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Court shoots down “continuation” strategy for expanding patents

April May 2024 Cantor Colburn IP Newsletter

A recent patent infringement ruling did more than just reverse a hefty damages award against Google. It also questions a common strategy used to obtain protection for new claims using an existing patent, and in turn provides accused infringers a potential avenue to invalidate the patents in question.

Discordant devices

The case involved patents owned by Sonos Inc. for managing groups of smart speakers in a multiroom system. They cover devices that implement overlapping speaker “zones” that share one or more speakers. So, for example, a speaker could belong to a group called “Morning,” as well as one called “Downstairs.”

In 2020, Sonos sued Google LLC, alleging it infringed the patents. A unanimous jury found that one patent was infringed and awarded Sonos $32.5 million in royalty-based damages.

The parties and the judge had agreed that the judge would evaluate certain affirmative defenses after the jury’s verdict. An affirmative defense is a legal reason why the defendant shouldn’t be held liable even if it committed the alleged acts. Google argued that Sonos’ patents were unenforceable under the affirmative defense of prosecution laches.

Music to Google’s ears

Generally, under the prosecution laches doctrine, a court can find a patent unenforceable if it was issued after an unreasonable and unexplained delay in the prosecution that prejudices others. The court found the doctrine applied here.

Sonos filed the provisional application on which the patents at issue claimed priority in September 2006. But it didn’t file applications for the two patents until April 2019, well after Google had disclosed the claimed invention to Sonos and, on its own, brought the invention to market.

The concern among patentees is that Sonos’ approach isn’t unusual. Sonos claimed that it diligently prosecuted the family of patent applications in the intervening 13 years. According to the court, the prosecution consisted of filing a corresponding nonprovisional application in 2007 and “a daisy chain of continuation applications” over the next decade. This is a common strategy employed to secure patent coverage for new market developments since the original filing date — what’s sometimes known as targeted continuation because it targets competitors’ products.

The court dismissed Sonos’ diligence, finding it didn’t render the delay any less unreasonable and inexcusable. In the court’s view, the diligent prosecution of patent applications in the interim in fact rendered the delay “all the more” unreasonable and inexcusable. Sonos easily could have amended its related applications to claim the invention or filed parallel applications with new claims covering it.

This wasn’t, the court emphasized, a situation where an inventor led the industry to something new. Rather, it 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.”

The court had little difficulty finding that Google suffered the necessary prejudice as a result of Sonos’ delay. Sonos itself had contended that Google invested in building out its line of products that infringed the patents and profited from the investment. It was undisputed that Google worked on, invested in and used the claimed technology during the period of Sonos delay.

Yet to be heard

The U.S. Court of Appeals for the Federal Circuit has never applied prosecution laches to patents issued before 1995, when changes to patent terms reduced the incentive to delay the issuance of a “submarine patent” that surfaces unexpectedly and catches competitors off guard. If the Federal Circuit upholds its application here, it may upend the practice of targeted continuations. Stay tuned.

© 2024

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