Inphi v. Netlist: Alternative Features Satisfy The Patent Written Description Requirement For A Negative Claim Limitation

It can be tricky to evaluate written description support under 35 U.S.C. § 112 for negative claim limitations since the support may amount to the absence of a feature from an invention that is described positively with respect to what it includes, as opposed to what it does not. The Court of Appeals of the Federal Circuit provided some clarity on this issue in Inphi Corp. v. Netlist, Inc., which is discussed below along with some practice tips in view of the decision.

The Federal Circuit held in Inphi Corp. v. Netlist, Inc. that describing alternative features, without identifying the comparative advantages or disadvantages of each feature, could constitute a "reason to exclude" to satisfy the written description requirement under 35 U.S.C. § 112 for a negative claim limitation under the Santarus standard, which states that "[n]egative claim limitations are adequately supported when the specification describes a reason to exclude the relevant limitation."