Whether, in inter partes review, the Patent Trial and Appeal Board may raise sua sponte a new ground of prior art that the petitioner neither cited nor relied upon—and whether the Board may rely on that new ground to reject a patent-holder's substitute claim as unpatentable

QUESTION PRESENTED The America Invents Act created inter partes review, an adversarial proceeding before the Patent Trial and Appeal Board in which third parties may challenge the patentability of an existing patent claim on the basis of prior art. In response to the petitioner’s challenge, the patentholder may amend the patent by offering substitute claims. The Act provides that “{iJn an inter partes review instituted under this chapter, the petitioner [has] the burden of proving a proposition of unpatentability.” 35 U.S.C. § 316(e). The question presented is: Whether, in inter partes review, the Patent Trial and Appeal Board may raise swa sponte a new ground of prior art that the petitioner neither cited nor relied upon—and whether the Board may rely on that new ground to reject a patent-holder’s substitute claim as unpatentable. (i)