Ever been accused of dragging your feet? Perhaps you took too long to start a project, respond to an email, or finally clean out the garage. Usually, the worst consequence is a grumpy spouse or a missed opportunity. But in the world of patents, delay can be a huge advantage. The delay I’m talking about is filing continuation applications to keep your options open at the United States Patent Office and to catch competitors who design around your patents. It’s been done for decades and is at the heart of the Google v Sonos case.

This case serves as a lesson in prosecution laches, a legal term for “you waited too long in the Patent Office, and that’s unfair.” The district court ruled that Sonos’ patents on multi-room “zone scene” technology were unenforceable because they delayed for years before adding key claims. The district court found that Sonos had committed prosecution laches. The Federal Circuit just reversed this decision, and the ongoing dispute provides useful guidance for anyone trying to get patents.

The District Court Drama

The story starts with a 2006 provisional patent application. Sonos kept the family alive with continuation applications but didn’t add the specific “overlapping zone” claims until 2019 right when Google was rolling out competing smart speakers.

Judge Alsup of the Northern District of California saw this as a classic ambush. He held that Sonos unreasonably and inexcusably delayed and that this delay prejudiced Google. To him, it looked like Sonos had waited in the weeds until the market developed, then whipped out claims designed to target a competitor’s existing products. That was enough, in his view, to trigger prosecution laches and wipe out Sonos’ $32 million jury verdict. (See my related article)

The Federal Circuit Encore

Fast forward to August 28, 2025. The Federal Circuit stepped in and said: not so fast.

The appellate court agreed that prosecution laches is real but reminded us that it requires more than mere delay. The challenger must demonstrate material prejudice, meaning the delay caused actual harm, such as making investments in ignorance of hidden claims.

Google couldn’t show material prejudice because Sonos’ application disclosure was made public in 2013, when its first patent issued. (Note: Sonos elected to keep their patent application secret until the patent issued, which is permitted.) This public disclosure of the details of the invention was before Google made any investments in its product. In other words, the public already had notice of the overlapping-zone idea even though it had not been claimed.

The Court stated that “[I]t is not improper for an applicant to broaden his claims during prosecution to encompass a competitor’s products, as long as the disclosure supports the broadened claims.”

Basically, the Court upheld the use of continuation applications to later broaden claims to catch a competitor. It isn’t material prejudice because the public is aware of everything that can be claimed in a patent application, because it is publicly available.

Why This Matters Beyond the Tech Titans

So, what does this courtroom drama mean for the rest of us? Three big takeaways:

1. Delay Alone Won’t Sink You. Continuation practice is alive and well. Just because you prosecute over many years doesn’t mean laches will apply. The key is whether your delay materially prejudiced someone else.
2. Disclosure Is Your Shield. Once your application publishes, competitors are on notice. If they invest anyway, it’s tough to argue surprise. The Federal Circuit leaned heavily on that here.
3. A Non-Publication Request could be an issue. Sonos requested that its patent application not be published, which is an acceptable practice. That is why the first publication occurred six years later, in 2013, when that patent was issued. If Google had made investments before 2013, there may have been a different result. This suggests that non-publication practice should be carefully considered.

The Takeaway

We often think of patents as rigid documents that remain unchanged from the day they are filed. But continuation practice gives you flexibility. It’s like having a “patent toolkit” you can open years later to craft claims that fit new market realities.

The Sonos-Google saga reminds us that patents are more than paperwork—they’re weapons, shields, and sometimes boomerangs.

For now, continuation practice remains a safe and vital part of the patent strategist’s playbook.

I’ve prepared a Guide and Checklist to help business owners identify their intellectual property. Click the button below to download a free copy.

Bill Honaker, “The IP Guy” is a former USPTO Examiner, a partner with Dickinson-Wright, and author of the new book, Invisible Assets – How to Maximize the Hidden Value in Your Business.

To get answers to your questions, let’s schedule a time to talk. You can access my calendar by clicking here, email Bill@IPGuy.com, or call me at 248-433-7381.