In the case of Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., the Supreme Court ruled on how appellate courts should review district court determinations in patent cases. The dispute centered around a drug called Copaxone which is used to treat multiple sclerosis and was patented by Teva Pharmaceuticals. Sandoz sought approval for a generic version of this drug, leading to litigation where Teva claimed that Sandoz had infringed upon their patent rights. Initially, the District Court sided with Teva but this decision was reversed by the Federal Circuit who concluded that certain claims in Teva's patent were indefinite and thus invalid. The Supreme Court held that when reviewing a district court’s resolution of subsidiary factual matters made in the course of its construction of a patent claim, an appellate court must apply clear error standard rather than de novo review (which allows fresh consideration). This means they cannot overturn such findings unless they have "a definite and firm conviction" that an error has been committed. This ruling clarified how much deference appeals courts should give to trial courts' interpretations during disputes over patents’ meanings - emphasizing more respect for lower-court fact-finding while leaving legal interpretation open for broader scrutiny.

In the dissenting opinion for TEVA PHARMS. USA, INC. v. SANDOZ, INC., Justice Thomas argued that the majority's decision to allow appellate courts to review factual findings in patent claim construction cases for clear error was a departure from precedent and could lead to uncertainty and inconsistency in future cases. He contended that patent claims should be treated as purely legal instruments subject only to de novo review by appellate courts, without deference given to district court's factual findings underpinning those claims. This approach would ensure uniformity of interpretation across different jurisdictions and reduce potential confusion or conflict between lower courts' interpretations of patents.