On June 16, 2015, the U.S. Court of Appeals for the Federal Circuit issued an en banc decision in Williamson v. Citrix Online, LLC et al. that changes the way courts should analyze means-plus-function elements under 35 USC 112, Paragraph Six.

Section 112, Paragraph Six permits a claim element to be drafted as a means for performing a specified function:

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.

It is important to determine whether a claim element is governed by Section 112, Paragraph Six, because of the language in the section that states that the claim element shall be construed, i.e., limited to covering only the corresponding structure, material or acts described in the specification, and equivalents thereof. This may render the claim element narrower than may otherwise appear. In other words, if the claim element is governed by Section 112, Paragraph Six, the claim element may not cover all structure that is able to perform the recited function.

Prior to the Williamson decision, the Court had held that the use of the word “means” in a claim element creates a rebuttable presumption that Section 112, Paragraph Six, applies, and that the failure to use the word “means” also creates a rebuttable presumption that Section 112, Paragraph Six, does not apply. In fact, the previous cases held that “the presumption flowing from the absence of the term ‘means’ is a strong one that is not readily overcome.” (emphasis in original).

However, in the Williamson decision, the en banc panel of the Federal Circuit held that:

Our consideration of this case has led us to conclude that such a heightened burden is unjustified and that we should abandon characterizing as “strong” the presumption that a limitation lacking the word “means” is not subject to § 112, para. 6 (emphasis added).

The Court did make clear that this change does not affect the corollary position, i.e., the "use of the word 'means' creates a presumption that § 112, ¶ 6 applies."

The result is that going forward, it will be easier for a court to determine that a claim element is governed by Section 112, Paragraph Six.

In recent years, the courts and the U.S. Patent & Trademark Office have taken the position that words other than “means” can be used to introduce a means-plus-function element, especially if such words are “nonce” words. “Nonce” words is a term that the courts and the U.S. Patent & Trademark Office have used to describe generic terms such as “mechanism,” “element” and “device” that “typically do not connote sufficiently definite structure” to invoke Section 112, Paragraph Six.

In the Williamson decision, the Court confirmed that "module" is a well-known "nonce" word that can operate as a substitute for "means" in the context of Section 112, Paragraph Six.

As set forth above, Section 112, Paragraph Six, also requires that the claim language be “without the recital of structure, material or acts in support thereof.” Prior to the Williamson decision, the Court had previously held that for a claim element to be interpreted under Section 112, Paragraph Six, the claim element must be essentially devoid of anything that can be construed as structure. However, in the Williamson decision, the Court also backed off such a strict requirement and held that the new 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.”

Again, the end result is that it will now be easier to find that a claim element is governed by Section 112, Paragraph Six.

There are actually two significant consequences of this new standard. First, as set forth above, if the claim element is found to be governed by Section 112, Paragraph Six, the scope of the claim element will be limited to the structure described in the specification that corresponds to the claimed function and equivalents thereof. Thus, there may be some narrowing of the scope of the element.

Because the provisions of Section 112, Paragraph Six will narrow the scope of the claim element to the disclosed embodiments (and equivalents thereof), it will likely be advantageous to describe several embodiments of the invention in the specification.

Furthermore, a second consequence is that there is an increased likelihood that such a claim element may be invalid under Section 112, Paragraph two, which requires that claims be sufficiently definite. In cases where the specification does not provide a clear description of the structure that performs the recited function, a court should find that the scope of the claim element is indefinite since a person of ordinary skill in the art would not be able to identify the corresponding structure and, thus, interpret the scope of the claim. As stated in the Williamson decision:

Even if the specification discloses corresponding structure, the disclosure must be of “adequate” corresponding structure to achieve the claimed function. Id. at 1311–12 (citing In re Donaldson Co., 16 F.3d 1189, 1195 (Fed. Cir. 1994) (en banc)). Under 35 U.S.C. § 112, paras. two and six, therefore, if a person of ordinary skill in the art would be unable to recognize the structure in the specification and associate it with the corresponding function in the claim, a means-plus-function clause is indefinite. Id. at 1312 (citing AllVoice Computing PLC v. Nuance Commc’ns, Inc., 504 F.3d 1236, 1241 (Fed. Cir. 2007)).

This latter issue has become a common problem in software-oriented inventions when an adequate description of the software or hardware that performs the recited function is not provided. In particular, the courts have frequently found that sufficient description is lacking when the specification merely states that the corresponding structure is a general purpose computer without providing any details of the algorithm related to the recited function.

Accordingly, care should be taken when defining inventions with functional language. In particular, when claiming a software-oriented invention, it is recommended to include an algorithm in the specification which describes the function set forth in the means-plus-function claim element. The Court has held that the “algorithm may be expressed as a mathematical formula, in prose, or as a flow chart, or in any other manner that provides sufficient structure. Noah, 675 F.3d at 1312 (citing Finisar Corp. v. DirecTV Grp., Inc., 523 F.3d 1323, 1340 (Fed. Cir. 2008)).”