Intervening Rights Cannot Be Triggered by Argument Alone in Reexaminations

March 15, 2012

Hunter Keeton

What This Means To You

  • The patent reexamination statute only triggers an intervening rights analysis for claims whose language is actually new or amended by the patentee.
  • Instead of amending original claims in reexamination, argue for their validity, saving any narrowing limitations for new claims added during the reexamination.


The Court of Appeals for the Federal Circuit (Federal Circuit) issued an en banc decision in Marine Polymer v. HemCon, on the topic of “intervening rights” for claims that are substantively changed in reexamination.

Where claims are narrowed by patentees during certain post-issuance proceedings before the US Patent and Trademark Office (PTO), the law of intervening rights protects accused infringers from facing liability for infringement during the period before the narrowed claims issue. In certain situations, intervening rights can limit patentees’ options even after the narrowed claims issue.

In this case, a divided court deemed that intervening rights can arise only for claims that have been added as new claims in a reexamination or for which the words were changed by amendment, and does not extend to claims that the patentee simply argued should be interpreted narrowly.


Marine Polymer, the patent holder, sued HemCon. The key claim term was “biocompatible.” The district court interpreted this term to mean “no detectable biological reactivity.” While the district court litigation was on-going, HemCon initiated an ex parte reexamination. The examiner initially rejected the claims, finding “biocompatible” meant “little or no bioreactivity.” In response, Marine Polymer argued the District Court got the claim interpretation right, and canceled dependent claims that specifically recited some small amount of bioreactivity.

The relevant independent claims were not amended. The examiner accepted Marine Polymer’s arguments, and allowed the independent claims. Before this happened, however, Marine Polymer won at the District Court and got damages and an injunction against HemCon. HemCon appealed.

Decision Analysis

In the original Federal Circuit panel decision, a majority opinion written by Judge Lourie agreed with HemCon who argued that Marine Polymer had amended its claims at least by argument during the reexamination, thus giving HemCon intervening rights. Judge Dyk dissented. Marine Polymer petitioned for en banc rehearing by the entire Federal Circuit, which was granted.

In the en banc decision, Judges Lourie and Dyk flipped positions between majority and dissent, so the en banc decision was the reverse of the panel decision. The Lourie majority found that the plain and unambiguous wording of the statute does not allow an interpretation of “amended” as meaning anything other than literally changed in some way. Because Marine Polymer never amended the actual claims at issue, this threshold requirement was not met, and intervening rights were not created. Dyk’s dissent argued that “amended” should not be interpreted so narrowly, but rather should extend to arguments raised in reexamination.

Because the 10 judges on the en banc decision split 5-5 on the issue of the District Court’s judgment, the majority opinion’s affirmance of the District Court does not have any binding or persuasive effect outside of this case. On intervening rights, the vote was 6-4, with Judge Linn providing the swing vote. But because the reexamination was not concluded at the time the District Court rendered its final judgment, the portions of the opinions on intervening rights are not binding precedent.

Nevertheless, since this is the best guidance we have on how the Federal Circuit judges see this issue, district courts are likelier to see the majority’s position as persuasive. Of course, later decisions by the Federal Circuit may change the landscape again.


This case supports the strategy many patentees already take in reexaminations: never amend the original claims, just try to argue their patentability, and save adding any narrowing limitations to try to get around the prior art for new claims. While this is often the best strategy, it may of course not work. The prior art may read on the original claims despite the patentee’s best arguments.

In addition, file history estoppel and claim scope disclaimer can still affect claim interpretation in reexaminations. So, even if arguments get the original claims through reexamination, their scope may still be narrowed so as to prevent infringement (though no intervening rights would be triggered).

This guidance on intervening rights applies to reexaminations only; a reissue does not have the same threshold issue that comes from the language in the reexamination part of the statute.

The America Invents Act passed last September is unlikely to change the outcome of this case in the future, as the relevant statutory language for post grant and inter partes review is the same. What may change the outcome in the future, however, is the sharp division between the judges on this issue, and the lack of clear precedential effect for this case.