A reissue application enables the owner of an already issued patent to correct defects in the patent. With its recent decision in In re Yasuhito Tanaka, the Federal Circuit Court of Appeals has expanded the reasons for pursuing a reissue. One result is that a patentee can now better fortify his patent in anticipation of suing for infringement.

The statute relating to reissues, 35 U.S.C. § 251, allows a patentee to make a correction if the claimed invention is either broader or narrower than what the patentee can rightfully claim.

More specifically, a patentee would want to narrow the scope of his patent if he finds a piece of prior art that would render at least the broadest claims invalid. In such a case, the patentee may fear that, in an infringement lawsuit, his broadest claims would be invalidated by this newly discovered prior art, so he preemptively seeks to narrow and thereby strengthen its patent.

By the same token, a patentee might seek to broaden the scope of his patent if he realizes, after the patent has issued, that he claimed his invention too narrowly. (Such a broadening reissue must be filed within two years of issuance and cannot “recapture” subject matter given up during the original prosecution of the patent.)

Yasuhito Tanaka filed a reissue application with broadened claims. After these broadened claims were rejected, Tanaka sought only to add dependent claims to his patent. The Patent and Trademark Office—through both an examiner and the Board of Patent Appeals and Interferences—rejected the new claims because Tanaka did not allege that his original patent claims were too broad.

As the PTO saw it, by keeping his broad patent claims unamended, Tanaka implicitly conceded that the claims were “not inoperative to cover the disclosed invention.” Because Tanaka did not specify an error that either broadens or narrows the scope of the claims of his issued patent, he did not meet the requirements of the reissue statute.

In reversing this judgment, the Federal Circuit ruled that a patentee may in fact seek a reissue application when he does not seek to give up his broadest claims but merely to add the narrower dependent claims. In its 2-1 decision, the Federal Circuit asserted that the case law supported Tanaka’s view that a reissue application may be filed merely to add a dependent claim.

The primary purpose of a dependent claim is to serve as a “back-up” position for the patentee: If, in the course of litigation, a broader, independent claim were to be invalidated—in light of the prior art, for example—a narrower, dependent claim may survive the invalidity attack. If this narrower claim covers the defendant’s product, the patentee’s lawsuit will be a success even though the patent’s broader claim was invalidated.

This decision provides a new reason for filing a reissue application, namely, to generate back-up positions through narrow dependent claims, in case one or more of the broader claims is invalidated during litigation. With these additional dependent claims, the chances increase that the patent will survive a validity attack with a claim that still covers the defendant’s product.

Sometimes, it is not until after a patent issues that a patentee realizes that additional dependent claims might prove important. If the patent is valuable enough and may become involved in litigation, a reissue application adding dependent claims should be considered. If the patent has been issued for less than two years, consideration should also be given to whether the claims are unduly narrow and might benefit from a broadening reissue.