Sonos, Inc. v. Implicit, LLC

An inter partes review (IPR) proceeding, captioned Sonos, Inc. v. Implicit, LLC, was filed by Sonos at the Patent Trial and Appeal Board (PTAB) of the U.S. Patent and Trademark Office. The case challenged the validity of a patent held by Implicit, LLC, a non-practicing entity (NPE) known for asserting its patent portfolio against technology companies. Sonos, the petitioner, is a well-known operating company that manufactures and sells wireless multi-room audio systems, including speakers and soundbars. The technology at the heart of this dispute involves methods for synchronizing the playback of content across multiple devices, a core feature of Sonos's product line.

The patent at issue in this IPR was U.S. Patent No. 8,942,252 B2, which is directed to a "method and system for synchronization of content rendering." Sonos initiated the IPR as a defensive measure, a common strategy for technology companies accused of infringement to challenge the validity of the asserted patents in a specialized administrative forum. The PTAB is often seen as a more favorable venue for accused infringers than district courts due to its lower burden of proof for invalidation and the technical expertise of its administrative patent judges. In a final written decision issued on September 16, 2019, the PTAB found the challenged claims of the '252 patent to be unpatentable.

This case is notable as an example of a frequent dynamic in patent litigation: an established technology manufacturer using the IPR process to invalidate patents asserted by an NPE. The dispute is also part of a larger landscape of intellectual property battles in the highly competitive smart speaker and wireless audio market, where major players like Sonos have been involved in high-stakes litigation against competitors like Google. The PTAB's decision was later appealed to the U.S. Court of Appeals for the Federal Circuit, which ultimately affirmed the finding of unpatentability. The appeal involved complex procedural issues, including a post-decision attempt by Implicit to correct the patent's inventorship, which the Federal Circuit ruled was forfeited due to its untimeliness.

Key Legal Developments and Outcome

This case summary details the parallel inter partes review (IPR) and the district court litigation between Sonos, Inc. and Implicit, LLC, concerning U.S. Patent No. 8,942,252.

Chronological Developments:

• 2017-03-10: District Court Complaint Filed. Implicit, LLC sued Sonos, Inc. in the U.S. District Court for the District of Delaware, alleging infringement of U.S. Patent Nos. 8,942,252 and 7,391,791. The case was docketed as Implicit, LLC v. Sonos, Inc., No. 17-cv-259.
• 2018-03: IPR Petitions Filed. Sonos filed two IPR petitions with the Patent Trial and Appeal Board (PTAB) challenging the validity of claims in both asserted patents. The petition challenging the '252 patent was assigned case number IPR2018-00767. Sonos argued the patents were unpatentable as anticipated or obvious in light of prior art, primarily U.S. Patent No. 7,269,338 to Janevski, which had a filing date of December 11, 2001.
• 2019-09-16: PTAB Final Written Decision. The PTAB issued final written decisions in both IPRs, finding all challenged claims of the '252 and '791 patents unpatentable. The Board rejected Implicit's argument that it had conceived of the inventions prior to the Janevski reference, finding the evidence of conception and communication to an engineer, Guy Carpenter, was insufficient.
• Appeal to the Federal Circuit. Implicit appealed the PTAB's decisions to the U.S. Court of Appeals for the Federal Circuit.
• 2019-10-31: Arthrex Decision. While the appeal was pending, the Federal Circuit issued its decision in Arthrex, Inc. v. Smith & Nephew, Inc., which held that the appointment of PTAB Administrative Patent Judges was unconstitutional.
• 2020-12-23: Remand to PTAB. Based on the Arthrex decision, the Federal Circuit granted Implicit's motion to vacate the PTAB's decisions and remand the case to allow Implicit to request a new hearing before a different panel or seek Director review.
• 2021-12-17: Request to Correct Inventorship. While the request for Director review was pending, Implicit filed a request with the USPTO to correct the inventorship of both patents to add engineer Guy Carpenter as a co-inventor.
• 2022-02-07: Director Review Denied. The USPTO Director denied Implicit's request for review of the original PTAB decisions.
• 2022-08: Certificates of Correction Issued. The USPTO granted the request and issued certificates of correction for both patents, officially adding Carpenter as an inventor.
• 2022-11-09: Second Remand to PTAB. The Federal Circuit again remanded the case to the PTAB for the limited purpose of determining what impact, if any, the certificates of correction had on the final written decisions.
• 2023-09-19: PTAB Decision on Remand. The PTAB concluded that Implicit was precluded from relying on the corrected inventorship. It held that Implicit had forfeited any new arguments based on the correction because it could have and should have raised the inventorship issue during the initial IPR proceeding. Implicit had all the necessary information from the start but made a strategic decision to argue that Carpenter's work "inured to the benefit" of the named inventors, rather than arguing he was a co-inventor.
• 2026-03-09: Federal Circuit Affirmance. Implicit appealed again, and the Federal Circuit affirmed the PTAB's decision on remand. The court held that while inventorship corrections under 35 U.S.C. § 256 are generally retroactive, they do not allow a party to undo a final decision by raising arguments that were forfeited. The court found that Implicit had waived its new inventorship-based theory by not pursuing it with diligence during the original proceedings and noted that the late change in strategy raised concerns of "sandbagging."
• Final Outcome. The Federal Circuit's decision affirmed the PTAB's finding that the challenged claims of U.S. Patent No. 8,942,252 are unpatentable. The case is closed at the appellate level, cementing the invalidity of the patent claims Sonos was accused of infringing. The parallel district court case, which was likely stayed pending the IPR and appeal, would be rendered moot by the final judgment of unpatentability.

Counsel for Petitioner Sonos, Inc.

Based on filings with the Patent Trial and Appeal Board (PTAB), the following attorneys from Paul Hastings LLP represented Sonos, Inc. in IPR2018-00767.

• Naveen Modi (Lead Counsel)

  • Firm: Paul Hastings LLP, Washington, D.C. office.
  • Note: Modi is the Global Co-Chair of the Intellectual Property practice at Paul Hastings and is widely recognized as one of the most active attorneys in post-grant proceedings, having handled over 600 IPRs and other PTAB trials.

• Joseph E. Palys (Counsel)

  • Firm: Paul Hastings LLP, Washington, D.C. office.
  • Note: Palys is a partner in the Intellectual Property practice and has extensive experience representing clients in IPRs and patent litigation, often alongside Naveen Modi.

• Quinn Smith (Counsel)

  • Firm: Paul Hastings LLP, Washington, D.C. office.
  • Note: Smith is an associate at the firm with a focus on post-grant proceedings before the PTAB.

• Irene Yang (Counsel)

  • Firm: Paul Hastings LLP, Palo Alto, CA office.
  • Note: Yang is an associate in the firm's Intellectual Property practice, focusing on patent litigation and PTAB trials.

Counsel for Patent Owner Implicit, LLC

Throughout the inter partes review and subsequent appeals to the Federal Circuit, patent owner Implicit, LLC was primarily represented by attorneys from Finnegan, Henderson, Farabow, Garrett & Dunner, LLP, and Ross M. Babbitt Co., LPA.

• Jason Lee Romrell (Lead Counsel)

  • Firm: Finnegan, Henderson, Farabow, Garrett & Dunner, LLP, Washington, D.C. office.
  • Note: Romrell argued for Implicit before the U.S. Court of Appeals for the Federal Circuit in the appeal of the PTAB's decision.

• Ross M. Babbitt (Counsel)

  • Firm: Ross M. Babbitt Co., LPA, Cleveland, Ohio.
  • Note: Babbitt is a litigation attorney whose practice includes intellectual property and a wide range of commercial disputes.

• Ahmed J. Davis (Counsel)

  • Firm: Fish & Richardson P.C., Washington, D.C. office.
  • Note: Davis is a prominent IP trial lawyer with extensive experience in complex patent litigation before federal district courts, the ITC, and the Federal Circuit. While he was listed on some filings, his active role in this specific IPR is not as clearly documented in the available public record as other counsel.

• Timothy P. McAnulty (Counsel)

  • Firm: Finnegan, Henderson, Farabow, Garrett & Dunner, LLP, Washington, D.C. office.
  • Note: McAnulty was part of the Finnegan team representing Implicit in its appeal to the Federal Circuit.

• J. Derek McCorquindale (Counsel)

  • Firm: Finnegan, Henderson, Farabow, Garrett & Dunner, LLP, Reston, VA office.
  • Note: McCorquindale focuses on patent litigation and was also on the briefs for Implicit's Federal Circuit appeal.