Litigating Patents – Reexamination Requests

After a patent is issued by the United States Patent and Trademark Office (USPTO), the discovery of prior art or publications not noticed prior to the patent’s issue may raise questions as to the validity of the issued patent. In such a case, a patentee or a third party may file an application for reexamination of the patent in the USPTO. For a third party, reexamination provides a lower cost alternative to a conventional lawsuit for challenging the validity of a patent. If the third party is an unsuccessful infringement defendant, a reexamination that results in the invalidation of a patent may provide vindication of that defendant’s rights despite the results of the court case. For the patentee, the reexamination process may reveal the need to narrow a patent’s claims in order to be in a better position to fend off a challenge to the patent’s validity. In addition, the USPTO may take it upon itself to reexamine a patent without it being requested by the patentee or a third party.

The patent reexamination process has two stages. At the outset, the USPTO determines whether a substantial new question of patentability is evident from the prior art or printed publications. If a need for reexamination is found, the patentee is given two months to provide a response to the USPTO, and a third-party reexamination requester may reply to the patentee’s response. In addition, the patentee is allowed to propose amendments to the patent claim or claims at issue as long as the amendments do not broaden the scope of the claims. When the patent reexamination process was initiated in 1980, the process was an ex parte process, meaning that once the process had been initiated and the parties’ responses were filed, only the USPTO was involved in the review of the reexamination application. Since 1999, an inter parties process has been allowed at the election of the applicant.


In an inter parties reexamination, the USPTO will send to the reexamination requester a copy of any communication that it sends to the patentee about the patent at issue. Each time a patentee files a response to any action by the USPTO concerning the challenged patent, the reexamination requester may file one response. In an inter parties reexamination, either party may appeal an adverse decision, in contrast to an ex parte reexamination, where only the patentee may appeal an adverse decision.

Although the inter parties reexamination procedure allows greater participation by the party challenging the patent, there are several drawbacks to the procedure. The application fee is nearly four times greater than for an ex parte reexamination. In addition, in an inter parties reexamination, the reexamination requester may not remain anonymous as in ex parte proceedings. Finally, although the inter parties requester is entitled to appeal an adverse decision, once the appeal process has been exhausted, an adverse decision against the requester is considered absolutely final and the requester may not bring a court action to challenge the same patent.

Once the reexamination process is completed for either an ex parte or inter parties reexamination, the Director of the USPTO issues and publishes a certificate that cancels any claim of the patent that is determined to be unpatentable, confirms any claim determined to be patentable, and incorporates any amended or new claim proposed during the reexamination process that is determined to be patentable.

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