Prosecution History Estoppel Bars Infringement Claim Under Doctrine of Equivalents

| Marissa M. RosenbaumChristie Matthaei


Before Moore, Reyna, and Stoll. Appeal from the United States District Court for the District of Nevada.

Summary: Claims for infringement under the doctrine of equivalents will be barred by prosecution history estoppel where plaintiff had both: (i) amended their claims, surrendering the claim scope subsequently occupied by defendant and (ii) clearly and unambiguously disclaimed such claim scope in office action responses, in an apparent effort to achieve patentability.

Pharma Tech Solutions filed suit against LifeScan, for infringement of its patents under the doctrine of equivalents. The district court found that LifeScan had not infringed Pharma Tech’s patents based on both amendment and argument-based estoppel, which prevented Pharma Tech from recapturing matter surrendered during prosecution.

On appeal, the Federal Circuit affirmed the district court decision, agreeing that both amendment and argument-based estoppel barred Pharma Tech’s infringement claim under the doctrine of equivalents. Regarding amendment-based estoppel, the Federal Circuit determined that Pharma Tech’s asserted equivalent was within the territory that Pharma Tech surrendered in an effort to differentiate from prior art during prosecution. Regarding argument-based estoppel, the Federal Circuit cited to Pharma Tech’s responses to multiple office actions where Pharma Tech argued that its amendment narrowed its claims to systems utilizing a particular procedure for accuracy, not used in LifeScan’s technology.

Editor: Paul Stewart