Reexamination is a process by which the United States Patent and Trademark Office reviews the validity of an issued U.S. patent upon limited grounds. Anyone can file a request for reexamination at any time during the enforceability period of the patent. The requestor must pay a filing fee ranging from $2,520 to $8,8001 depending on the type of request, and the request must include all of the following requirements: (a) a statement pointing out each substantial new question of patentability, (b) identifying every claim for which reexamination is sought, (c) providing an explanation of the art applied to the claims, (d) supplying a copy of the art relied upon, (d) presenting a copy of the specification and claims, and (e) providing a certificate that the patent owner has been served. For requirement (d), reexamination may only be based on patents and printed publications.

Two types of reexamination exist—(1) ex parte reexamination and (2) inter partes reexamination. For ex parte reexamination, once an individual submits the request for the reexamination, they can no longer actively participate in the proceedings—only the Patent Examiner and the Patent Owner are involved. During inter partes reexamination, however, the third party requestor may participate in all aspects of the reexamination. This includes allowing the third party to submit correspondence opposing a Patent Owner’s response to an Office Action. Inter partes reexamination is relatively new and is only available for cases filed on or after November 29, 1999.

Recent trends show the increasing importance of inter partes reexamination. Parties are increasingly using inter partes reexamination as a way to advance and sometimes resolve ongoing litigation and reduce litigation costs.2 Trends show that most judges are likely to grant stays of litigation until reexamination proceedings in the Patent and Trademark Office cease.3 According to a recent study, judges granted stays 72 percent of the time in a survey of 83 cases requesting such stays.4 Since the commencement of inter partes reexamination in 1999, requests for stays in litigation due to the reexams have risen drastically. The table and graph below show the increases over the past five years.5 In addition, according to the United States Patent and Trademark Office, of the inter partes reexams that had been recently completed as of 2007, patent claims were invalidated 88 percent of the time.

These trends highlight the increasing importance of inter partes reexamination as a means for resolving patent disputes. In addition, reexamination proceedings are decided in accordance with unique rules and procedures established by the U.S. Patent and Trademark Office, and appearances before the Patent and Trademark Office are limited to registered patent attorneys and agents. Accordingly, these trends also highlight the increasing importance of registered patent attorneys, knowledgeable in reexamination practice, on any patent litigation team.