The Limits of Claim Differentiation

Abstract

The process of claim construction is the most important part of patent litigation. Courts employ a number of rules, or canons, to reach an understanding of what patent claims mean. Of these, the doctrine of claim differentiation has arguably had the most significant impact on claim construction. Understood most broadly, the claim differentiation doctrine provides that no two claims in the same patent should be interpreted to have the same scope. As a general matter, applying the doctrine of claim differentiation results in broader constructions of patent claims, because it is most commonly used to prevent defendants from limiting a broad genus claim to the range of embodiments actually disclosed or more explicitly recited in other claims. Sometimes this is the right result, because defendants are improperly seeking to limit broader genus claims to the preferred embodiments disclosed in the specification. But at other times it leads to problematic results by expanding claims to cover things the patentee never intended. In this Article, I conduct an empirical review of claim differentiation decisions in the Federal Circuit and in the district courts, and I suggest limiting