In a recent memorandum opinion, Judge Leonard P. Stark found that plaintiff did not overcome its presumption of prosecution history estoppel and therefore entered judgment in favor of defendant on plaintiff’s claims of infringement under the doctrine of equivalents for claims 1, 3, and 6 of U.S. Patent No. 5,865,866 (“the ‘866 Patent”), and claim 2 of U.S. Patent No. 5,873,862 (“the ‘862 Patent”). ICU Medical, Inc. v. Rymed Technologies, Inc., C.A. No. 07-468-LPS (D. Del. Sept. 30, 2013). This opinion comes after a May 2012 bench trial, where Judge Stark considered “the viability of the jury’s verdict of infringement under the doctrine of equivalents, in light of prosecution history estoppel.” Id. at 1.The parties were in agreement that “the presumption of prosecution history estoppel applies, and further agree[d] that [plaintiff had] an opportunity to attempt to rebut that presumption by showing that the rationale for the amendment bore no more than a tangential relation to the equivalent in question.” Id. at 7.
First, Judge Stark found that plaintiff failed to carry its burden in establishing that the amendments 1, 3, and 6 of the ‘866 Patent “bore no more than a tangential relation to the equivalent in question.” Id. at 7, 20. Judge Stark noted, among other things, that “[t]he prosecution history is silent as to why [plaintiff] followed the Examiner’s recommendation and added the configuration limitations and not just the O-ring elements limitation that [plaintiff] believed was necessary to overcome the prior art rejection. Simply following the Examiner’s unexplained suggestion, without any explanation from [plaintiff], does not, on this prosecution history, suffice to satisfy the tangentiality exception.” Id. at 14. Judge Stark also noted “the Court is unable to conclude, on the record before it, that the PTO necessarily would have allowed an amended claim 1” without the limitations that plaintiff claimed were tangential to patentability (i.e., configuration limitations). Id. at 16.
Judge Stark similarly found that plaintiff failed to carry its burden in overcoming the presumption of prosecution history estoppel with respect to claim 2 of the ‘862 Patent. Id. at 20. Judge Stark noted that with respect to claim 2, plaintiff had a “stronger argument that there is an objectively discemable reason for the amendment, an amendment which added the O-ring elements but no additional limitations relating to their configuration.” Id. at 19-20. However, “the Court [was] uncertain whether “the ‘equivalent in question’ [was] the O-ring elements.” Id. at 20. As Judge Stark explained, the finding of infringement of equivalence may have been predicated on a finding of the presence of O-ring elements only by equivalence, yet the existence of O-ring elements was not tangential to the claim amendment.” Id.