2013 Decision On Assignor Estoppel Designated As Precedential By PTAB

The Patent Trial and Appeal Board designated as precedential its October 25, 2013, decision to institute inter partes review and declined to apply the doctrine of assignor estoppel as an exception to 35 U.S.C.§311(a). Section 311(a) provides that "a person who is not the owner of a patent may file with the Office a petition to institute an inter partes review of the patent."

Here, the petitioner filed a petition for inter partes review, arguing that U.S. Patent No. 7,670,536, which relates to injection molding machines, was invalid under §§ 102 and 103. In its preliminary response, the patent owner claimed that the petitioner is barred from challenging the validity of the patent under the doctrine of assignor estoppel. The doctrine of assignor estoppel prohibits an assignor of a patent, or one in privity with him, from challenging the validity of that patent when he is sued for infringement by the assignee. See Semiconductor Energy Laboratory Co., Ltd. v. Nagata, 706