Claim construction is central to virtually every patent case. The patent claims define the limits of the invention. Often, the meaning of terms in a patent claim determines whether the accused infringer’s product or process infringes the patent. Typically, a patent owner wants a broad meaning in order to capture the accused infringer’s product, while the accused infringer wants a narrower meaning that excludes its product. Interpreting the meaning of a patent claim may seem a straightforward exercise but, more often than not, that is simply not the case.

The meaning of patent claims usually rests on the “intrinsic evidence.” Intrinsic evidence consists of the claim language, the written description in the patent, and the prosecution history, which includes all communications with the Patent Office made during the patent application process. The prosecution history may include statements by the patent applicant as to what his or her invention does or does not cover. Because of the high cost of patent litigation and the future of a business potentially at stake, parties often also attempt to rely on “extrinsic evidence” in hopes of persuading a court to adopt their view of the intrinsic evidence. Extrinsic evidence commonly consists of testimony or affidavits by experts in the field of the invention about what the words of the patent claims would mean to a person of ordinary skill in the art. Although courts find extrinsic evidence of lesser significance than intrinsic evidence and do not permit extrinsic evidence to contradict intrinsic evidence, judges may still rely on extrinsic evidence in their claim construction analyses.

Until recently, review of a district court’s patent claim construction was conducted by the U.S. Court of Appeals for the Federal Circuit “de novo,” making its own interpretation and giving no deference to the lower court’s determinations. However, on January 20, 2015, the Supreme Court decided Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., somewhat altering this standard of review. The Supreme Court held that, while the ultimate determinations on claim construction are issues of law and, therefore, are reviewed de novo, underlying factual issues resolved by the district court should be given deference and are instead subject to a “clear error” standard of review. For example, a district court judge’s consideration of testimony by expert witnesses, and the judge’s decision on the weight to be given such testimony, are now entitled to deference on appeal.

Whether in practice the holding of Teva ends up substantially changing the law of claim construction remains to be seen. In the handful of claim construction cases reviewed by the Federal Circuit since Teva, the court has made note of Teva, but found that, because the district court judge did not rely on extrinsic evidence to construe the patent claims, review of the district court’s claim construction remained de novo.

In its first post-Teva decision, In re Papst Licensing Digital Camera Patent Litig., the Federal Circuit avoided a deference inquiry. The parties disputed whether the district court judge had relied on expert testimony in its decision or not. The Federal Circuit found that “the district court relied only on the intrinsic record, not on any testimony about skilled artisans’ understandings of claim terms in the relevant field….”  In so doing, the Federal Circuit avoided the issue of deference, and treated the entire claim construction question de novo. Similarly, in other post-Teva Federal Circuit cases involving claim construction, the Federal Circuit found that the district court did not rely on extrinsic evidence in arriving at its claim construction and, therefore, conducted its review de novo. See Fenner Investments, Ltd. v. Cellco Partnership; Lexington Luminance LLC v.Amazon. com Inc.; and FenF, LLC, v. Smartthingz, Inc.

The Federal Circuit’s post-Teva cases expose some open issues. Although the Supreme Court made clear that claim construction is de novo when a district court has not relied on extrinsic evidence, and that factual findings resolving a dispute between experts are reviewed for clear error, other scenarios are less clear. How will the Federal Circuit treat the situation where the district court did rely on extrinsic evidence as part of its claim construction determination, but such reliance was improper because the intrinsic evidence fully resolved the construction issue? For example, what if a district court judge relies on expert testimony, but the Federal Circuit decides that it was unnecessary to have gone beyond the intrinsic evidence to construe the claims? The impact of Teva in such a situation remains to be seen.

Sources: Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., 135 S. Ct. 831, 841 (2015); In re Papst Licensing Digital Camera Patent Litig., No. 2014-1110 (Fed.Cir. Feb. 3, 2015); Fenner Investments, Ltd. v. Cellco Partnership, No. 2013-1640 (Fed. Cir. Feb. 12, 2015); Lexington Luminance LLC v. Inc., No. 2014-1384 (Fed. Cir. Feb. 9, 2015); FenF, LLC, v. Smartthingz, Inc., 2014-1490 (Fed. Cir. Feb. 6, 2015).