Addressing the issue of de novo versus differential claim construction review post-Teva, the Supreme Court of the United States remanded back to the U.S. Court of Appeals for the Federal Circuit a case where de novo review was applied to a disputed claim term. CSR PLC v. Azure Networks, LLC, Case No. 14-976 (Supr. Ct., Apr. 20, 2015). 

In January 2015, the Supreme Court ruled in Teva v. Sandoz that the Federal Circuit must generally apply a “clear error” standard when reviewing a district court’s claim construction that is not based on intrinsic claim construction evidence.

In the present case, the plaintiff Azure Networks sued CSR, alleging that the defendant’s products infringed Azure’s patent on Bluetooth technology. After the district court construed the patent term “MAC address,” the district court entered judgment in favor of CSR, finding non-infringement of the Azure patent. Azure appealed, and the Federal Circuit, in a split panel decision issued just two months prior to the Teva ruling, reversed the district court’s construction and found in favor of Azure.

CSR filed a petition for writ of certiorari to the Supreme Court, arguing that the Federal Circuit reviewed the district court’s construction under the de novo standard of review, contrary to the Supreme Court’s Teva decision. The petition highlighted the Federal Circuit’s use of “dictionaries not in the record” as “extrinsic evidence,” now subject to a clear error review. Specifically, CSR argued that the Federal Circuit made “factual findings contrary to those of the district court without identifying clear error.”

The question presented was as follows:

Did the United States Court of Appeals for the Federal Circuit err in using a de novo standard of review instead of a “clear error” standard of review in reviewing the factual findings made by the . . . District Court while construing the term “MAC Address” . . . ?

The Supreme Court issued a one-page order, remanding the case back to the Federal Circuit for further consideration in light of Teva