The Court creates a hybrid standard of review.

On January 20, in Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc.,^[1] the U.S. Supreme Court altered the U.S. Court of Appeals for the Federal Circuit’s longstanding de novo standard of review for all claim construction in patent infringement cases. The Supreme Court instead instructed the Federal Circuit to use a hybrid approach: When reviewing a district court’s subsidiary factual findings that relate to extrinsic evidence, the Federal Circuit must now apply a “clear error” standard of review, but when reviewing a district court’s findings based on evidence intrinsic to the patent, the Federal Circuit will continue to apply de novo review.^[2] The ultimate question of construction will remain a legal question.^[3]

In 1996, in Markman v. Westview Instruments, Inc.,^[4] the Supreme Court announced that “the construction of a patent, including terms of art within its claim,” is not for a jury but “exclusively” for “the court” to determine. Post-Markman, the Federal Circuit began reviewing district court claim constructions de novo.^[5] The Federal Circuit recently revisited this issue en banc in Lighting Ballast Control v. Philips Electronics.^[6] Guided by the principle of stare decisis, a split Federal Circuit in Lighting Ballast held that it would continue to review district court claim construction de novo.

However, nearly 20 years after Markman, and just a few months afterLighting Ballast, the Supreme Court has shifted the legal framework and once again rejected the Federal Circuit’s approach. In a 7-2 decision, the Supreme Court relied heavily on Federal Rule of Civil Procedure 52(a)(6), which instructs courts of appeals that they “must not . . . set aside” a district court’s “[f]indings of fact” unless they are “clearly erroneous” and ruled that there was no reason to deviate from that rule when it comes to factual findings related to claim construction.^[7] The Court explained thatMarkman “neither created, nor argued for” an exception to Rule 52(a) and instead held only that the ultimate issue of the proper claim construction should be treated as a question of law.^[8]

In cases such as Teva, where the district court relied on extrinsic evidence to establish proper claim constructions, the Court concluded that “[t]his factual determination, like all other factual determinations, must be reviewed for clear error.”^[9] The Court noted that “[a] district court judge who has presided over, and listened to, the entirety of a proceeding has a comparatively greater opportunity to gain that familiarity than an appeals court judge who must read a written transcript or perhaps just those portions to which the parties have referred.”^[10]Although it may be simpler for an appellate court to review the entirety of the district court’s claim construction de novo rather than to apply two separate standards, the Court further pointed out that courts of appeals have long found it possible to separate factual matters from legal matters.^[11]

Finally, the Court addressed concerns that “clear error” review would result in less uniformity.^[12] It concluded that neither the Federal Circuit nor the involved parties had shown that divergent claim construction that stems from divergent findings of fact (on subsidiary matters) would occur more than occasionally. After all, the Court noted, the Federal Circuit will continue to review de novo the district court’s ultimate interpretation of the patent claims.^[13]

The dissent, authored by Justice Clarence Thomas and joined by Justice Samuel Alito, argued that claim construction does not involve findings of fact, so Rule 52(a)(6) should not apply.^[14] It noted that the subsidiary determinations about patent claims that the majority identified as factual do not concern historical facts, but rather concern “legal fictions,” such as how a skilled artisan would understand a given term or phrase at a given point in time. According to the dissent, the skilled artisan inquiry “more closely resembles determinations categorized as ‘conclusions of law.’”^[15] Finally, the dissent argued that the need for uniformity in claim construction also weighs heavily in favor of de novo review of subsidiary evidentiary determinations^.[16]

Teva will likely have a significant impact on patent litigation and patent appeals. Certainly, litigants should expect more disputes about whether a court’s ultimate claim construction was based on determinations regarding extrinsic or intrinsic evidence. On one hand, the “hybrid” standard may lead courts to defer claim construction, which potentially makes early resolution of cases more difficult. On the other hand, cases may be more likely to settle post-claim construction. Finally, whether the majority or the dissent is right about the threat of inconsistent rulings remains to be seen.