Indefinite, but Obvious and Anticipated? Federal Circuit Tells PTAB Certain Indefinite Claims May Be Anticipated or Obvious

Patent claims that could be indefinite have long raised tricky issues for parties in IPR.  Should petitioners challenge in IPR claims they think are indefinite? What should the PTAB do if it concludes that the claims are indefinite? The Federal Circuit’s recent decision in Samsung Electronics Co. v. Prisua Engineering Corp. provides some answers.

The key questions addressed in the case were, first, whether the PTAB may cancel claims for indefiniteness once IPR has been instituted on another grounds, such as anticipation under section 102 and obviousness under section 103. And second, whether the PTAB is strictly precluded from making anticipation and obviousness determinations on indefinite claims.

In the IPR, the Board concluded that certain of the challenged claims were indefinite under IPXL Holdings, LLC v., Inc. because they covered both an apparatus and method, and thus a manufacturer or seller would not know when infringement occurred. The PTAB declined to cancel the claims, however, explaining its understanding that the PTAB does not have the authority to cancel claims for indefiniteness and cannot evaluate indefinite claims for anticipation or obviousness determinations.  

On appeal, the Federal Circuit held that the PTAB got it half right. While the Federal Circuit agreed that the PTAB’s cancellation authority in IPR is limited to the grounds on which IPR may be instituted – anticipation under section 102 and obviousness under section 103, the Federal Circuit disagreed that the PTAB could not make that determination as to certain claims that are indefinite.

In particular, the Federal Circuit held that even when a claim is indefinite under IPXL for reciting elements of an apparatus and a method, the PTAB is not necessarily precluded from assessing patentability on section 102 and 103 grounds. The Court explained that a claim is indefinite under IPXL for “purposes of determining when infringement occurs,” but IPXL “does not speak to whether the claim is also invalid for obviousness.” 

Consequently, the Federal Court remanded the IPR back down to the PTAB, with instructions to determine whether the claims the PTAB found indefinite are unpatentable as anticipated or obvious based on the instituted grounds.


The Federal Circuit’s decision opens some doors and closes other. It clarified that the PTAB’s authority to cancel claims in IPR extends only to grounds that can be raised under sections 102 and 103. 

However, the Court also held that, in some situations, the PTAB can make anticipation and obviousness determinations for claims that are indefinite under IPXL. The major question moving forward will be whether any other types of indefinite claims may properly be evaluated for anticipation and obviousness in IPR.

Another question that the Federal Circuit left unresolved is what is required to show anticipation or obviousness of indefinite claims. By their nature, indefinite claims have insufficiently certain scope.  How then can the PTAB determine whether the prior art is within that scope?

Another issue to watch for is whether IPR estoppel under section 315(e) will apply when the PTAB cannot reach a final decision as to patentability of claims because of indefiniteness. The Federal Circuit noted in a footnote that estoppel would not apply, but another case will be needed to test the issue.