Ex parte reexamination Edit
The PTO traditionally has employed an ex parte reexamination procedure. At any time during the term of the patent, any person may request reexamination by the PTO of any claim of a patent on the basis of prior patents or printed publications cited under 37 C.F.R. 1.501. The request must be in writing and must be accompanied by payment of a reexamination request filing fee as set forth in 37 C.F.R. 1.20(c). If the request raises a substantial new question of patentability affecting any claim of the patent, reexamination is commenced. The same ex parte procedures that apply to initial examinations govern traditional reexamination. Patentees often invoke reexamination themselves, seeking to insulate their patents from late-surfacing prior art by cutting back the claims. Potential infringement defendants frequently forgo reexamination, preferring the safeguards available in court and fearing that reexamination might weaken their position in litigation.
Inter partes reexamination Edit
Since 1999 patent law has also provided an inter partes reexamination proceeding. Any person at any time may request such a proceeding, and if the request identifies a substantial new question of patentability, the PTO Director opens an inter partes proceeding. The procedures parallel those of initial examinations, but require service of documents on the third-party requester and permit the requester to file written comments each time the patent owner files a response to an action on the merits. The requester thus has some ability to participate in writing, but no opportunity for discovery, cross-examination, or oral presentations. Third-party requesters are estopped from asserting in litigation the invalidity of any claim on any ground that the requester “raised or could have raised” during the inter partes proceeding. Prior to enactment of a statutory amendment in November 2002, requesters could not appeal adverse decisions to the federal courts. Inter partes reexamination has been rarely used due to concerns with the estoppel and (original) appeal provisions as well as fears that reexamination would unduly favor the patentee as reasons why inter partes reexamination has been virtually ignored.
Limitations on reexamination Edit
Both types of reexamination limit the issues that may be considered. The proceedings are confined to issues of novelty and nonobviousness based on prior art in the form of patents or printed publications. Reexamination does not permit challenges to enablement, written description, best mode, or utility.