TAKEAWAY: Post-grant proceedings can be useful tools for correcting or amending a patent. Changes to the patented claims, however, may provide a third party with a defense against infringement under the doctrine of intervening rights. Patent holders and third parties alike should be cognizant of the contours of the doctrine due to its potential effect on the infringement of patents.

The USPTO provides a number of post-grant mechanisms that can be used to correct or amend an issued patent, including reissue, reexamination, inter partes review (IPR), post grant review (PGR), and covered business method review (CBM). Amending the issued patent may involve amending the patented claims. Changes to patented claims may give rise to intervening rights as a defense to infringement. For example, if a claim of an original patent does not cover an act of a third party, but is broadened via a broadening reissue to cover the act, the third party may raise intervening rights as a defense against the broader claim. In a less common scenario, the narrowing of a claim can trigger intervening rights. Here, a claim of an original patent may already cover an act of a third party, but the claim may be invalid in view of prior art. If the claim is then narrowed with new features to avoid the invalidating prior art, while still covering the act, the third party may raise intervening rights as a defense against the narrower claim. While the doctrine of intervening rights is outlined in 35 U.S.C. § 252 in the context of reissue, the provisions of Section 252 are also applicable to reexamination, IPR, PGR, and CBM by statute.

As an initial matter, when claims of a patent, after having gone through a post grant proceeding, are substantively different than the original claims in the patent, intervening rights may arise. The intervening rights doctrine provides two defenses to patent infringement. The first defense is a mandatory or absolute defense for certain infringing acts performed prior to grant of a reissued patent or issuance of a certificate after reexamination, IPR, PGR, or CBM. The second defense is a discretionary or equitable defense for substantial preparations to perform certain infringing acts that were made prior to the grant of reissue or issuance of the certificate. Courts may consider a number of factors to determine whether the equitable defense applies, including, for example, whether the infringer continued manufacturing before the grant of reissue or issuance of the certificate on advice of its patent counsel; whether there were existing orders or contracts; whether non-infringing goods can be manufactured from the inventory used to manufacture the infringing product and the cost of conversion; whether there is a long period of sales and operations before the grant of reissue or issuance of the certificate, from which no damages can be assessed; and whether the infringer has made profits sufficient to recoup its investment.

With this in mind, a patent holder may consider whether intervening rights will apply when deciding whether or not to add a new claim or amend a claim in a post grant proceeding. If, for example, the patent holder has the option of achieving its goal through argument alone, or amending with the language of a dependent claim, such a strategy may be worth pursuing before making new claim amendments that could trigger the intervening rights doctrine. On the other side, third parties may consider whether they can avail themselves of the intervening rights doctrine against patents, and should be aware of the limitations of the intervening rights doctrine in terms of the time periods covered, and the factors/requirements that must be present for the intervening rights doctrine to apply.