On June 16 2015 the Federal Circuit, in affirming the invalidity of certain patent claims as indefinite under 35 USC § 112(2), revised the law on construing means-plus-function claim limitations under 35 USC § 112(6) and provided guidance on what disclosure must be provided in the patent specification for performing the claimed functions. The decision in Williamson v Citrix Online, LLC is of particular significance because Part II.C.1 of the opinion, regarding the standard for means-plus-function claim limitations, was considered and decided by the court en banc, with the opinion of the court being written by Judge Linn. Judge Newman wrote a dissenting opinion regarding Part II.C.1.


Means-plus-function claiming is authorised by 35 USC § 112(6), which provides that an element in a patent claim for a combination may be expressed as a "means" of performing a specified function without the recital of supporting structure, material or acts, and that such a claim will be construed to cover the corresponding structure, material or acts described in the specification and equivalents thereof.

In determining whether a claim limitation is to be construed as a means-plus-function limitation under 35 USC § 112(6), the Federal Circuit has long recognised the importance of the presence or absence of the word 'means'. The Federal Circuit had previously stated in Personalized Media Communications, LLC v International Trade Commission(1) that the use of the word 'means' creates a rebuttable presumption that Section 112(6) applies, while the absence of the word 'means' similarly creates a rebuttable presumption that Section 112(6) does not apply.

The underlying subject matter of the patent at issue, US Patent 6,155,840 (the '''840 patent'), related to methods and systems for conducting "distributed learning" that utilise industry standard computer hardware and software linked to a network to provide a "virtual classroom" environment, allowing one or more presenters to connect with geographically remote audience members. Claim 8 thus was directed to a system for conducting distributed learning that included, among other features, a "distributed learning control module for...coordinating the operation" of a "streaming data module". Notably, the claim did not use the word 'means' in its language.

Where a functional claim limitation lacks the word 'means', the Federal Circuit has previously held that the presumption that Section 112(6) does not apply can nonetheless be overcome where the claim term fails to "recite[ ] sufficiently definite structure" or else recites "function without reciting sufficient structure for performing that function".(2)

However, the Federal Circuit has more recently established a heightened burden for overcoming the presumption that Section 112(6) does not apply to a limitation expressed in functional language that fails to use the word 'means'. In Lighting World, Inc v Birchwood Lighting, Inc(3) the Federal Circuit first applied a different standard, holding that "the presumption flowing from the absence of the term 'means' is a strong one that is not readily overcome". In Flo Healthcare Solutions, LLC v Kappos(4)the Federal Circuit raised the bar even further, declaring that:

"[w]hen the claim drafter has not signaled his intent to invoke § 112, ¶ 6 by using the term 'means,' we are unwilling to apply that provision without a showing that the limitation essentially is devoid of anything that can be construed as structure."

Williamson decision

In the en banc portion of Williamson v Citrix Online, LLC, the court overruled that portion of Flo Healthcare requiring "a showing that the limitation essentially is devoid of anything that can be construed as structure". The Federal Circuit held that such a heightened standard is improper and also expressly overruled the characterisation of the rebuttable presumption as "strong" that Section 112(6) does not apply in the case where a limitation lacks the word 'means'. According to the en bancdecision, when a claim term lacks the word 'means', the proper standard for overcoming the presumption that Section 112(6) does not apply is whether the claim term fails to "recite sufficiently definite structure" or else "recites function without reciting sufficient structure for performing that function". The converse presumption remains unaffected - that is, "use of the word 'means' creates a presumption that § 112, ¶ 6 applies".(5)

Applying this new standard, the Federal Circuit construed "distributed learning control module" as a means-plus-function claim limitation governed by 35 USC § 112(6), despite the absence of the word 'means', based on use of the nonce word 'module', finding that neither the term 'module' nor the prefix 'distributed learning control' imparts structure to the limitation.

Having found the presumption against means-plus-function claiming to have been rebutted and "distributed learning control module" subject to 35 USC § 112(6), the Federal Circuit next found that the specification did not disclose sufficient corresponding structure to perform the "coordinating function". Accordingly, the claims at issue were held to be indefinite. According to the court, the specification of the '840 patent made clear that the specialised function to be performed by the "distributed learning control module" must be implemented in a "special purpose computer" - which the court explained was "a general purpose computer programmed to perform particular functions pursuant to instructions from program software". The court stated that in cases involving means-plus-function claim limitations subject to Section 112(6) requiring implementation in a special purpose computer, the specification must disclose an algorithm for performing the claimed function. The court determined that no such algorithm was disclosed in the specification of the '840 patent corresponding to the claimed "coordinating function" of the "distributed learning control module"; thus the claims were held to be indefinite.

In his opinion, which concurred in part, dissented in part and provided additional comments, Judge Reyna concurred with the conclusions that the claim term "distributed learning control module" is governed by Section 112(6) and indefinite under Section 112(2). However, he questioned whether the majority opinion sidestepped underlying fundamental issues involving the development of functional claiming law and suggested the need to revisit the judicially created Section 112(6) presumptions.

In a dissent from the en banc ruling, Newman disagreed with elimination of the word 'means' as a statutory signal for a means-plus-function claim construction, believing that resorting to nonce words such as 'module' is inappropriate to confer means-plus-function status. According to Newman, the majority opinion will lead to additional uncertainty, confusion in claim interpretation, litigation and disincentive to patent-based innovation.

For further information on this topic please contact Diego Scambia or Daniel Apgar at Fitzpatrick, Cella, Harper & Scinto by telephone (+1 212 218 2100) or email ( or The Fitzpatrick, Cella, Harper & Scinto website can be accessed at


(1) 161 F 3d 696, 703-04 (Fed Cir 1998).

(2) Watts v XL Sys, Inc 232 F 3d 877, 880 (Fed Cir 2000).

(3) 382 F 3d 1354, 1358 (Fed Cir 2004).

(4) 697 F 3d 1367, 1374 (Fed Cir. 2012).

(5) Personalized Media, 161 F 3d at 703.

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