Background
Prisua Engineering Corp. owned a patent covering a digital video processing system for capturing and editing video in real time. Samsung Electronics America filed a petition for inter partes review (IPR), challenging the patent’s claims as obvious and anticipated based on prior art. The Patent Trial and Appeal Board instituted the IPR and ultimately found some claims unpatentable.
During the IPR, the Board encountered claim language it found difficult to construe: claims using the term “digitally controlled video integrated circuit” invoked what the Board concluded was indefinite claim language, potentially meeting the definition of a means-plus-function claim that lacked adequate structural disclosure. The Board addressed this by canceling some claims as indefinite — using a § 112 invalidity ground — even though indefiniteness is not a ground available in IPR proceedings.
Prisua appealed the Board’s cancellation of certain claims. Samsung cross-appealed, challenging the Board’s failure to address other claims it contended were unpatentable.
The Court’s Holding
The Federal Circuit held that the PTAB exceeded its statutory authority when it canceled claims for indefiniteness. Under 35 U.S.C. § 311(b), an IPR petition may only challenge the validity of a patent on the grounds of prior art — that is, lack of novelty under § 102 or obviousness under § 103. Indefiniteness under § 112 is not an available ground in IPR. The Board cannot import it through the back door of claim construction.
The court explained what the Board should do instead when it encounters claims it cannot construe with reasonable certainty: it must either decline to institute the IPR as to those claims (if the issue arises before institution) or, if the indefiniteness becomes apparent during trial, conclude in its final written decision that it cannot determine whether the claims are unpatentable under § 102 or § 103. The proper result is a determination that the petitioner has failed to prove unpatentability, not a cancellation on § 112 grounds.
The Federal Circuit also addressed the claim construction issue directly and found that the claims at issue were not in fact means-plus-function claims requiring § 112 structural disclosure, and vacated the Board’s ruling on those claims.
Key Takeaways
- The PTAB cannot cancel patent claims for indefiniteness in an IPR proceeding — that authority is limited to the district courts and the ITC, where the full range of validity challenges is available.
- When the Board cannot construe a claim with reasonable certainty during an IPR, the appropriate result is to decline institution or to find that the petitioner failed to prove the claim unpatentable on prior art grounds — not to cancel it on § 112 grounds.
- Patent owners facing IPR challenges on potentially indefinite claims should consider whether to raise the indefiniteness issue in district court, where the presumption of validity applies and the full range of § 112 defenses is available.
- IPR petitioners who believe challenged claims are indefinite face a strategic dilemma: they cannot win an indefiniteness finding from the PTAB, but an IPR trial on the merits may result in a “no determination” outcome that leaves the patent in place.
Why It Matters
Samsung v. Prisua draws a firm line around the PTAB’s authority in IPR proceedings. The ruling reinforces that Congress designed IPR as a streamlined, focused proceeding limited to prior art challenges — it is not a wholesale substitute for district court litigation where all validity defenses are available. This has important strategic consequences for both patent owners and alleged infringers.
For defendants challenging patents in both IPR and district court simultaneously, this decision clarifies that indefiniteness arguments must be preserved and pursued in court, not at the PTAB. For patent owners with claims that may have § 112 vulnerabilities, the ruling provides some protection from PTAB cancellation on those grounds, while underscoring that exposure in district court litigation remains real. The decision also clarifies the mechanics of IPR trial management when claim construction is uncertain, providing clearer guidance to the Board on how to handle potentially indefinite claims without overstepping its statutory authority.