In Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., 135 S. Ct. 831 (2015) (No. 13-854), the Supreme Court addressed the standard of review the Court of Appeals should apply when reviewing patent claim constructions that involve a district court’s resolution of an underlying factual dispute.  The Court abrogated prior Federal Circuit precedent and held that in such cases, the appellate court must apply a “clear error,” not a de novo, standard of review to factual determinations.  The Court reasoned that the “clear command” of FRCP 52(a)(6) – stating that a court of appeals must not set aside a district court’s factual findings unless they are clearly erroneous – must apply to reviews of a district court’s resolution of subsidiary factual matters made in the course of its construction of a patent claim.  The Court concluded that its prior patent rulings, including Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996), did not create or imply any exception to Rule 52(a), and even if exceptions to the rule were permitted, the Court found no convincing ground for creating such an exception here.  The Court clarified that the appellate courts can still review a district court’s ultimate claim construction de novo, as that ultimate interpretation is a legal conclusion; but, to overturn a judge’s resolution of an underlying factual dispute, a Court of Appeals must find that the judge, in respect to those factual findings, has made a clear error.