The Role of Intrinsic Evidence in Construing Means-Plus-Function After Williamson

Under 35 U.S.C. § 112(f) (or pre- AIA § 112 ¶ 6), claims can be written in a “means-plus-function” format. In a typical case, means-plus-function claims recite a “means for [performing some function]” and cover only those structures in the patent’s specification capable of performing that function. Limitations that do not use the word “means” can still be treated as means-plus-function limitations if they do not “recite sufficiently definite structure.” This can be a problem if the patent drafter did not intend its claim terms to be treated as “means-plus-function” and failed to disclose the necessary structure in the specification. In such cases, a means-plus-function construction can be fatal. Until 2015, there was a “strong presumption” that claim limitations, which did not expressly recite the word “means” or “step” should not invoke means-plus-function treatment under § 112(f). But in the face of increasingly functional software claiming, an en-banc Federal Circuit in Williamson v. Citrix Online, LLC removed the heightened evidentiary showing. Under Williamson, “the presumption can be overcome and § 112, ¶ 6 will apply if the challenger demonstrates that the claim term fails to ‘recite sufficiently definite structure’ or else recites ‘function without reciting sufficient structure for performing that function.’” In the immediate aftermath of Williamson, some practitioners noted the court’s holding may “affect the scope and validity of claims for tens of thousands of patents in a way unintended by the drafters of those claims.” Now five years later, various cases have relied on Williamson and applied Williamson’s standards to specific fact patterns. In this article, Finnegan attorneys Dan Cooley and Alex Harding explore the nuances of two such cases where the Federal Circuit analyzed the intrinsic record—the claim language, specification, and prosecution history—to reach different conclusions under 35 U.S.C. § 112(f). Read the full article here.