Phillips v. AWH Corp.
In Phillips v. AWH Corp., the U.S. Court of Appeals for the Federal Circuit clarified en banc that the proper approach to claim construction in challenges to the validity of patents, and the Court established guiding principles for determining the hierarchy and weight of the definitional sources that give a patent its meaning.
Specifically, the Court held that a patent term should be construed to be "the meaning that the term would have to a person of ordinary skill in the art in question at the time of ... the effective filing date of the patent application." Phillips, 415 F.3d 1303, 1313 (Fed. Cir. 2005).
In litigation, courts thereby seek to understand "the words of the claims themselves, the remainder of the specification, the prosecution history, and extrinsic evidence concerning relevant scientific principles, the meaning of technical terms, and the state of the art." Id. at 1314 (quoting Innova/Pure Water, Inc. v. Safari Water Filtration Sys., Inc., 381 F.3d 1111, 1116 (Fed. Cir. 2004)).
This is an approach more favorable to patent-holders than the "Broadest Reasonable Interpretation" standard that was used by the Patent and Trademark Office until October 2018, when it was replaced by the PTO with this Phillips standard.