In March 2026, the Federal Circuit delivered a significant ruling in the case of Implicit, LLC v. Sonos, Inc., addressing the interplay between inter partes review (IPR) proceedings and the retroactive correction of inventorship. The court’s decision underscores the importance of timely action in patent litigation and clarifies the limitations of retroactive corrections in the context of IPRs.
The dispute centered on U.S. Patent Nos. 7,391,791 and 8,942,252, owned by Implicit, LLC. Sonos, Inc. challenged these patents through IPR proceedings, leading the Patent Trial and Appeal Board (PTAB) to invalidate several claims based on prior art. Following these decisions, Implicit sought to amend the inventorship of the patents by adding a new inventor, aiming to establish an earlier priority date and circumvent the prior art cited by Sonos.
Implicit argued that the certificates of correction, which retroactively added the new inventor, should influence the PTAB’s final written decisions. However, the Federal Circuit rejected this argument, emphasizing that while corrections under 35 U.S.C. § 256 are generally retroactive, parties can forfeit the ability to rely on such corrections if they fail to pursue them with reasonable diligence during ongoing proceedings. The court noted that Implicit had the relevant evidence from the outset but did not act promptly, raising concerns of “sandbagging”—a strategy where a party withholds a known issue to gain a tactical advantage later.
This ruling highlights several critical points for legal professionals:
- Timeliness in Addressing Inventorship Issues: Parties must address inventorship concerns early in PTAB proceedings. Delayed corrections may be deemed untimely and ineffective.
- Limitations of Retroactive Corrections: While inventorship corrections are retroactive, they do not automatically reopen concluded proceedings. Courts may apply doctrines like forfeiture or waiver when arguments are introduced belatedly.
- Consistency in Litigation Strategy: Introducing new theories or corrections after adverse decisions can weaken a party’s position and may be viewed unfavorably by the court.
The Federal Circuit’s decision in this case serves as a cautionary tale for patent holders, emphasizing the necessity of proactive and timely actions in patent litigation to avoid procedural pitfalls.