By: Diana Faust and Benton Williams
In early 2015, the Supreme Court of the United States announced its opinion in Teva Pharms. USA, Inc. v. Sandoz, Inc. There, the Supreme Court affirmed the general rule that a district court’s construction of claim limitations remains a legal question reviewed de novo. The Supreme Court explained that district courts may consider extrinsic evidence, such as expert testimony and other external sources, and that any subsidiary factual findings that underlie the district court’s claim construction are reviewed for clear error. The court made clear that experts 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. Thus, if a district court resolves a dispute between experts and makes a factual finding that, in general, a certain term of art had a particular meaning to a person of ordinary skill in the art at the time of the invention, the district court must then conduct a legal analysis: whether a skilled artisan would ascribe that same meaning to that term in the context of the specific patent claim under review.
Early this year, the U.S. Court of Appeals for the Federal Circuit issued opinions in a number of patent appeals addressing and applying the proper scope and construction of disputed claim limitations. In Akzo Nobel Coatings, Inc. v. Dow Chem. Co., the court affirmed summary judgment of noninfringement of a patent pertaining to an extrusion process generating low viscosity dispersions. Relying on the import of the word “collection” in the disputed claim limitation “pressurized collection vessel,” the court affirmed the district court’s construction as requiring a “buildup or accumulation of material.” The court explained that construing “collection” to mean “receive,” as Akzo proposed, would render the claim term “collection” superfluous. The Federal Circuit next considered expert testimony proffered to create a genuine issue of material fact as to literal infringement, but concluded that such testimony failed to raise a fact issue where the expert’s opinions were ambiguous on the issue of whether dispersion “accumulates” in the heat exchangers. Thus, the court affirmed the district court’s judgment where Akzo failed to raise a genuine issue of material fact as to Dow’s alleged infringement because the material in Dow’s process did not accumulate, but rather flowed continuously to an un-pressurized collection vessel.
Subsequent to Akzo, the Federal Circuit addressed its review of the construction and scope of disputed claim limitations by district courts in Eon Corp. IP Holdings, LLC v. Silver Spring Networks, Inc. The parties in Eon disputed the meaning of several claim terms, including “portable” and “mobile.” The district court determined during claim construction that the disputed terms should be given their plain and ordinary meaning. The parties continued to dispute the construction of the disputed terms throughout trial and presented conflicting expert testimony as to the proper construction of “portable” and “mobile.” Eon’s experts testified that “portable” simply meant something that was “capable of being easily moved . . . but not that it actually has to move.”  They opined that the terms would include anything that was movable, which could include a house. Rejecting the expert testimony and interpretations of Eon’s experts and entering a judgment of no infringement, the Federal Circuit held that Eon’s expert opinions were completely untethered to the context of the invention in the case. The court expressed that “[u]nder no permissible construction of the terms “portable” and “mobile”—given their ordinary meaning in the context of the [patents at issue]—could a reasonable jury have found [infringement].”
Applying Teva, these recent opinions demonstrate the proper use of expert testimony in patent claim construction: to explain terms of art and the state of the art at any given time. The Federal Circuit, on review, is not hesitant to adopt a district court’s determination that expert testimony is ambiguous or not credible, and it will not consider expert testimony when used to prove the legal construction of a writing.
 ___ U.S. ___, 135 S.Ct. 831 (2015).
 Id. 841-42.
 Id. at 841.
 811 F.3d 1334 (Fed. Cir. 2016).
 Id. at 1341, 1343.
 Id. at 1340.
 Id. at 1339.
 Id. at 1341.
 No. 2015-1237, ___ F.3d ___, 2016 WL 766661 (Fed. Cir. Feb. 29, 2016).
 Id. at *6.
 Id. at *6.