Federal Circuit Relaxes Standard for Imposing Means-Plus-Function Limitations When the Term 'Means' Is Not Used

On June 16, 2015, the U.S. Court of Appeals for the Federal Circuit issued a partial en banc decision clarifying the standard to determine whether a patent claim limitation lacking the word "means" is in fact a means-plus-function limitation subject to the strictures of 35 U.S.C. § 112, para. 6 (now 35 U.S.C. § 112(f)). In Williamson v. Citrix Online, LLC, et al., No. 2013-1130, the Federal Circuit overruled its decade-old precedent that established a strong and not readily overcome presumption that a claim limitation expressed in functional language without use of the word "means" is not governed by Section 112, para. 6. This decision will implicate both patent prosecution and litigation—as prosecutors will find it harder to avoid drafting claims that do not invoke "means-plus-function" limitations, and defendants may find it easier to construe claims narrowly by arguing for such "means-plus-function" constructions, as well finding such claims invalid for lack of an enabling disclosure. 

The Federal Circuit in Williamson held that the applicable standard is "whether the words of the claim are understood by persons of ordinary skill in the art to have a sufficiently definite meaning as the name for structure." The Federal Circuit further explained that when the word "means" is not used, the presumption that Section 112, para. 6 does not apply can be overcome if it is demonstrated that the claim term fails to "recite sufficiently definite structure" or else recites "function without reciting sufficient structure for performing that function." 

Means-plus-function claiming permits a patentee to express a claim limitation in terms of a function to be performed. In doing so, specific constraints are placed on how the limitation will be construed. Specifically, claim scope will be restricted to only the structure, materials, or acts described in the patent specification that correspond to the claimed function and equivalents thereof. The governing statutory provision states:

An 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, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.

35 U.S.C. § 112, para. 6.

Because prior precedent can only be overruled by an en banc court, the particular portion of the opinion addressing the proper standard to determine whether a claim limitation lacking the word "means" is a means plus function limitation was decided en banc. In its en banc analysis, the Federal Circuit noted the importance of the presence or absence of the word "means" in a claim limitation when determining whether Section 112, para. 6 is invoked. When a claim limitation uses "means," there is a rebuttable presumption that the statute applies. Conversely, when "means" is not used, there is a rebuttable presumption that the statute does not apply. The Federal Circuit surveyed its relevant precedent over the past ten years and noted that it had elevated the evidentiary standard for overcoming the presumption that Section 112, para. 6 does not apply when "means" is not used in a claim limitation. In particular, the Federal Circuit had determined that the presumption is "a strong one that is not readily overcome," and found the statute inapplicable "without a showing that the limitation essentially is devoid of anything that can be construed as structure." The Federal Circuit reversed course, finding that any heightened burden to overcome the presumption is unjustified, and going forward will abandon characterizing the presumption as a strong one. The Federal Circuit noted that such a "characterization is unwarranted, is uncertain in meaning and application, and has the inappropriate practical effect of placing a thumb on what should otherwise be a balanced analytical scale." Furthermore, the Federal Circuit eliminated the requirement that there be "a showing that the limitation essentially is devoid of anything that can be construed as structure."

At issue were claims directed to distributed learning (e.g., remote instruction via a "virtual classroom") systems and methods, and in particular the claim term "distributed learning control module." The word "means" is not used in the claims at issue. In an earlier decision issued in November 2014, the Federal Circuit vacated the district court's determination of invalidity and concluded that the "strong" presumption that Section 112, para. 6 does not apply was not overcome. See 770 F.3d 1371 (Fed. Cir. 2014). The Federal Circuit withdrew that earlier decision and, based on its return to a traditional view of the applicable presumption when "means" is not used, held the "distributed learning control module" limitations to be means-plus-function and invalid as indefinite for failing to comply with Section 112, paras. 2 and 6.

The Federal Circuit noted that even with the absence of the word "means," the claim limitations were drafted in a format consistent with traditional means-plus-function limitations and the "distributed learning control module" term simply substituted the well-known "nonce" word "module" for "means." The Federal Circuit further noted that the term "module" does not provide any indication of structure corresponding to the recited functions ("receiving communications …"; "relaying the communications …"; and "coordinating the operation of the streaming data module"). The Federal Circuit concluded that the "distributed learning control module" limitation is written in means-plus-function format that requires the specification to disclose sufficient structure corresponding to the claimed functions. Regarding the "coordinating" function, the Federal Circuit agreed with the district court that adequate structure is not disclosed in the specification. Specifically, the Federal Circuit found, based on the patent's disclosure, that a special purpose computer is required to implement the distributed learning control module. Accordingly, disclosure of an algorithm for performing the claimed "coordinating" function was required, whether expressed as a mathematical formula, in prose, or as a flow chart, or in any other manner that provides sufficient structure. Finding no such disclosure in the specification, and rejecting the contention that extrinsic expert testimony was sufficient to create adequate disclosure, the Federal Circuit affirmed the district court's judgment of invalidity for indefiniteness for failure to comply with Section 112, paras. 2 and 6.

For patent prosecutors, no longer will the use of "nonce" words, such as "module," "device," or "unit" likely be sufficient to avoid finding the limitation to be in means plus function form. To avoid unintentionally invoking Section 112, para. 6, claim drafters should ensure to include sufficient structure in their patent claims and throughout any amendment process. As an added safety net, where function figures prominently in a claimed invention, the specification should be drafted with sufficient detail to ensure that adequate structure corresponding to the claimed functionality is clearly disclosed. At bottom, when a means-plus-function claim is not desired, patent prosecutors should be mindful of reviewing patent applications and amendments to ensure that the new threshold announced in Williamson for invoking Section 112, para. 6 is avoided.