Patent law has long recognized the need to claim an element in terms of the desired function of the element rather than any specific structure or material of the element itself. Congress codified this need stating that “[a]n element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof. . . .”1 Recognizing, however, that this could potentially lead to extraordinarily broad claim coverage, Congress limited the scope of such claims to “the corresponding structure, material, or acts described in the specification and equivalents thereof.”2
This particular method of patent claiming has become known as “means plus function” claiming, because courts have historically held that a presumption exists that this section applies when a claim uses the word “means” followed by a recitation of function.3 The Federal Circuit has held that when the claim does not use the word “means,” a rebuttable presumption exists that means plus function limitations do not apply.4 Moreover, for a long time, the Federal Circuit held “that the presumption flowing from the absence of the term ‘means’ is a strong one that is not readily overcome.”5 However, in Williamson v. Citrix Online, LLC, the Federal Circuit recently has taken a step back from their prior precedent on the issue of means plus function limitations.6 Specifically, the Court held that “[h]enceforth, we will apply the presumption as we have done prior to Lighting World, without requiring any heightened evidentiary showing and expressly overrule the characterization of that presumption as ‘strong.’”7
While the Federal Circuit intended to repudiate the idea that the form of a patent claim—whether or not the claim uses the word “means"—should trump the actual function or intent of the claim, the decision merely weakened the presumption instead of abolishing it entirely.8 The Court left it to the lower courts to decide when the presumption has been properly rebutted. As of the time of this article, district courts have had at least twenty-two opportunities to address whether or not the presumption against means plus function limitations not involving the word “means” had been properly rebutted. In nine instances, despite the lowered standard, the court found insufficient evidence to rebut the presumption. However, in eleven instances, the court found sufficient evidence that the claim language did, in fact, invoke the means plus function limitations of § 112(f). Furthermore, in two instances, the court analyzed multiple terms for the same patent using the reduced standard articulated in Williamson, and found that some terms invoked means plus function limitations while others did not.
District courts are attacking the issue by focusing on an analysis of the language of the claims in question as well as the corresponding specifications. Courts do not appear to focus on specific words or phrases alone to trigger whether or not means plus function limitations apply. Several courts looked at the term “processor”—a term specifically addressed inWilliamson as invoking means plus function limitations—and found that the term did not invoke § 112(f),9 but at least one court disagreed.10 In GoDaddy.com, LLC v. RPost Commc'ns Ltd., the U.S. District Court for the District of Arizona relied on Williamson to develop a two-pronged test to determine if the term “processor for associating” was a means plus function limitation: “whether the term ‘processor’ (1) fails to recite sufficiently definite structure or (2) recites function without reciting sufficient structure for performing that function.”11 The Court looked to the intrinsic record to find that although the term “processor” provides some measure of structure, the specification did “not convey to a skilled artisan anything about the internal components, structure, or specific operation of the processor.”12 Because the structure provided was not sufficient to perform the claimed function, the defendants successfully rebutted the presumption.13
Although the Federal Circuit weakened the presumption, however, does not mean that it is dead. In M2M Sols. LLC v. Sierra Wireless Am., Inc., the U.S. District Court for the District of Delaware addressed whether or not the term “processing module”—module being another means plus function term in Williamson—invokes § 112(f).14 The plaintiff provided expert testimony that the claim as a whole provided sufficient structure, and although the Court had some reservations, it noted that “Defendants do not establish by any evidence—let alone clear and convincing evidence—that the above claim limitation does not provide sufficient algorithmic structure.”15 Because the defendants failed to present sufficient evidence, the Court held that the presumption applied and, therefore, there was no means plus function limitation.16
While it is still too early to determine what exactly the impact of the reduced burden will be, it is clear that lower courts are attempting to apply the reduced standard for rebutting the presumption as articulated in Williamson by looking to substantive evidence provided by the parties. Although explicit means plus function claiming by the use of the term “means” has reduced in recent popularity, it appears likely that courts could continue to find means plus function limitations in other less explicit terms.