In Inphi Corp. v. Netlist, Inc., Appeal No. 2015-1179, the Federal Circuit affirmed that a negative claim limitation satisfied the standard for written description because the specification included alternative features that were properly described.

Inphi filed for inter partes reexamination of Netlist’s patent directed to computer memory technologies.  During reexamination, Netlist narrowed the claims by adding a negative limitation that excluded certain signal types.  The narrowed claims issued, and Inphi appealed to the PTAB.  Inphi argued that the negative limitation did not satisfy the standard for written description because the patent did not disclose a reason for excluding the recited signal types.  The PTAB affirmed the examiner’s decision, finding that the specification contained sufficient support because it adequately distinguished between the signal types at issue.

The Federal Circuit affirmed the PTAB decision and confirmed that the specification contained sufficient description.  The Federal Circuit clarified its language from the case Santarus, Inc. v. Par Pharmaceutical, Inc., 694 F.3d 1344, 1351 (Fed. Cir. 2012), which states that “[n]egative claim limitations are adequately supported when the specification describes a reason to exclude the relevant limitation.” The Federal Circuit held that Santarus did not create a heightened written-description standard for negative claim limitations and that if alternative elements are positively recited in the specification, they may be explicitly excluded in the claims.