In a major patent infringement decision, the U.S. Supreme Court has limited ability to the U.S. Court of Appeals for the Federal Circuit's ability to second-guess trial courts when making crucial claims construction decisions.

The high court's 7-2 decision in Teva Pharmaceuticals USA Inc. v. Sandoz Inc. finds that the appellate court charged with hearing the nation's patent infringement cases can no longer use a “de novo” review standard when assessing the factual determinations a trial judge makes when determining the key words in patent claim. Instead, the Federal Circuit can only review such fact-based rulings under a “clear error” standard.

The high court established in 1996's Markman v. Westview Instruments that claims construction claim questions are matters of law for a judge—not a jury to decide—and such rulings will be reviewed de novo at the Federal Circuit.