Maschoff Brennan



Is the Role of the Expert Witness in Claim Construction Changing?

April 1, 2016

The proper role of extrinsic evidence in claim construction, in particular expert witnesses, has long been a matter of some debate. The Federal Circuit has been fairly consistent in characterizing extrinsic evidence as less important than the intrinsic record (the patent and its prosecution history) when construing claim terms. However, because claim construction focuses on construing claim terms “as understood by one of ordinary skill in the art,” litigants, and courts, have been equally consistent turning to expert witnesses having “ordinary skill in the art” (or speaking for one having such skill).

Recent case law has arguably shed some light on what the proper role is for expert witnesses in claim construction going forward. The possible takeaways are that (1) experts can no longer offer their opinions as to the legal aspects of claim construction, e.g., the meaning compelled by the contextual analysis of the intrinsic record, and (2) expert testimony, even if limited to factual matters, will be irrelevant on appeal (and will not trigger the deferential “clear error” standard of review) if the intrinsic record is clear.

The Supreme Court in Teva Pharm. USA, Inc. v. Sandoz, Inc. (Teva II), 135 S. Ct 831 (2015), set out to resolve the standard of review for claim construction findings. The Court clarified that the meaning of claim language is a legal issue entitled to de novo review, but that subsidiary factual findings are reviewed under the “clearly erroneous” standard. The ultimate question of claim construction remains, however, a legal conclusion:

The district judge, after deciding the factual dispute, will then interpret the patent claim in light of the facts as he has found them. This ultimate interpretation is a legal conclusion. The appellate court can still review the district court’s ultimate construction of the claim de novo. But, to overturn the judge’s resolution of an underlying factual dispute, the Court of Appeals must find that the judge, in respect to those factual findings, has made a clear error

Teva II, 135 S. Ct. at 838–39. The Court premised its conclusion, at least in part, on the legal principle that “[e]xperts may be examined to explain terms of art, and the state of the art, at any given time, but they cannot be used to prove the proper or legal construction of any instrument of writing.” Id. at 841 (citations and internal quotation marks omitted).

In the wake of Teva II, the Federal Circuit has done two noteworthy things. First, it has embraced the Supreme Court’s observation regarding the proper role of experts and interpreting legal writings by emphasizing that “[e]xperts may explain terms of art and the state of the art at any given time, but they cannot be used to prove the legal construction of a writing.” Teva Pharm. USA, Inc. v. Sandoz, Inc. (Teva III), 789 F.3d 1335, 1339 (2015). Putting a finer point on the subject, “[a] party cannot transform into a factual matter the internal coherence and context assessment of the patent simply by having an expert offer an opinion on it.” Id. at 1342. The clear implication of this is that the Federal Circuit takes a dim view of efforts to invoke the clear error standard of review simply by citing an expert, because no fealty is owed an expert’s views on legal conclusions such as the ultimate issue of claim construction. Going forward, expert testimony regarding the legal meaning of claim language in light of the patent itself and its prosecution history may be vulnerable to attack.

The other thing the Federal Circuit has done following Teva II is to develop a line of cases supporting the view that, even if a district court made subsidiary factual findings on which it based its claim construction, the appellate court need not consider those findings on review if the intrinsic record itself is sufficient for determining a legal meaning of the claim language. See, e.g., Eidos Display LLC V. AU Optronics Corp., 779 F.3d 1360 (Fed. Cir. 2015). Thus, the Federal Circuit has limited the circumstances in which it will apply a clear error review in claim construction, consequently limiting the utility of extrinsic evidence in claim construction.

Based on the subsequent case law, examples of acceptable reliance on expert testimony in claim construction include:

  • “to explain terms of art, and the state of the art, at any given time,” Teva III, 789 F.3d at 1339;
  • to resolve factual disputes regarding technical words, such as the terms “microparticles” and “nanoparticles,” Cephalon, Inc. v. Abraxis Bioscience, LLC, 618 Fed. Appx. 663, 665-666 (Fed. Cir. 2015); or
  • to “shed useful light on the relevant art” to allow the court to understand the perspective that one skilled in the art brings to bear on the claimed invention, Shire Development, LLC v. Watson Pharmaceuticals, Inc., 787 F.3d 1359, 1364–65 (Fed. Cir. 2015).

An expert witness’s usefulness, or even admissibility, beyond these examples may be questionable. Indeed, an argument can be made that it is improper for an expert witness to give any contextual analysis of the intrinsic evidence or give ultimate conclusions as to how the court should interpret claim language. See, e.g., TomTom, Inc. v. Adolph, 790 F.3d 1315, 1326 (refusing to apply clear error review regarding an expert’s opinion on prior art distinctions made in the specification and prosecution history because “the prosecution history is part of the intrinsic evidence, which this court reviews de novo”).

Going forward, litigants should be aware of potential attacks against claim construction experts that stray too far towards providing a legal conclusion or ultimate construction of claim terms. It seems reasonably clear that experts can testify regarding the state of the art at the time of the invention, the meaning of relevant technical terms or language outside the context of the patent, and any other factual matters that help the court understand the perspective of one skilled in the art at the time of the invention. In this sense, experts still provide value to claim construction. A possible interpretation of the Federal Circuit’s application of Teva II, however, is that their role has been somewhat diminished.

R. Parrish Freeman

Taylor J. Wright