Hospira, Inc. v. Eli Lilly and Company

This Court has long recognized the doctrine of prosecution history estoppel, which provides that when a patentee narrows a claim during patent prosecution for a “substantial reason related to patentability,” “the court should presume that the patentee surrendered all subject matter between the broader and the narrower language,” and therefore may not reclaim that subject matter under the doctrine of equivalents. Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 740 (2002). In Festo, this Court held that “[t]here are some cases, however, where the amendment cannot reasonably be viewed as surrendering a particular equivalent.” Id. at 740. One such scenario arises when “the rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question.” Id. The Court then went on to hold that “[t]he patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent.” Id. at 741. The question presented is: Whether a patentee may recapture subject matter via the doctrine of equivalents under the “tangential relation” exception by arguing that it surrendered more than it needed to during prosecution to avoid a prior art rejection, even if a claim could reasonably have been drafted that would literally have encompassed the alleged equivalent.