The Supreme Court recently decided a patent case involving a significant procedural issue.  In Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., 135 S.Ct. 831 (1/20/15), the question before the Court was whether the Federal Circuit Court of Appeals should review a district court’s factfindings in its claim construction decision under a de novo or a “clearly erroneous” standard.   The Court held that the proper standard of review, under Federal Rule of Civil Procedure 52(a)(6), is “clearly erroneous.”  The case establishes a two-part standard of review of a district court’s claim construction decision: a clearly erroneous standard for subsidiary facts and a de novo standard for the question of law.

The case involved Teva Pharmaceuticals’ patent for a method of making a drug to treat multiple sclerosis.  Sandoz began to sell a generic version of the drug.  Teva Pharmaceuticals sued Sandoz for patent infringement.  The claim at issue referred to a polymer having a specific molecular weight.  Sandoz argued that Teva Pharmaceuticals’ patent was invalid because the term “molecular weight” was indefinite.  Sandoz contended that there were three possible meanings of “molecular weight,” and that the patent did not explain which one was to be used.

The district court held that the patent was valid, based on expert testimony, finding that the term “molecular weight” was definite to a person skilled in the art.