Ex parte reexamination may be requested by either a patent owner or a third party in order to challenge the novelty or nonobviousness of one or more claims in a patent. The scope of prior art submitted in support of the challenge is limited to printed publications and patents, while other types of prior art (such as product prior art) are cannot be raised in a request for ex parte reexamination.

A request for ex parte reexamination can be filed at any time after a patent is granted and up to six years after it expires (a case-by-case determination may result in longer or shorter applicable time periods). A third party’s involvement generally ceases after the party files the request (the third party could have the ability to response to a patent owner’s statements, but those patent owner’s statements are rarely filed). Upon review, the central reexamination unit of the US Patent and Trademark Office (USPTO) will decide whether submitted prior art raises a substantial new question of patentability. Although ex parte reexaminations may take several years to conclude, as there is no statutory time limit for concluding the proceedings, but the USPTO does conduct ex parte reexaminations with “special dispatch” (i.e., these proceedings are supposed to move as fast as possible).

Like inter partes review (IPR) and post-grant review (PGR), ex parte reexamination is a cost-effective alternative to using litigation to challenge patent validity, and the standard for proving that a claim is unpatentable is lower during an ex parte reexamination than during a litigation. Unlike IPR and PGR, there is no legal estoppel that can be imposed on the requester later on. The most important benefit of an ex parte reexamination request is that it can be submitted anonymously, a benefit that is not available for IPR and PGR proceedings.

Substantial risks from ex parte reexaminations exist because the patent owner has the ability to amend claims, add new claims, and interact with the patent examiner without any input from the third-party requester. Thus, a patent owner might be able to further improve their patent during an ex parte reexamination, so this risk must be carefully considered in making a decision as to whether the procedure should be used.

Ex parte reexamination is not only available to potential infringers, as patent owners can also consider using the proceedings to test (or improve) an issued patent. A patent owner looking to assert its patent, and therefore anticipating an invalidity challenge, may choose to initiate an ex parte reexamination before any litigation in order to resolve any anticipation or obviousness concerns about the patent. Having survived an ex parte reexamination, the patent then becomes more difficult to invalidate in a court proceeding on similar challenges.

[View source.]