Williamson Decision Will Encourage Patent Defendants to Challenge Software Claims

In Williamson v. Citrix Online, announced on June 16, the Court of Appeals for the Federal Circuit ruled in a partially en banc opinion that claims expressed in terms of functionality can be subject to statutory requirements for means-plus-function claims, even if they do not use the word “means” and instead use phrases such as “a mechanism for” or “a device for.”

It has long been the case that for means-plus-function claim limitations implemented by a special-purpose computer, there must be an algorithm disclosed in the specification for performing the function, or the claim is indefinite.  Prior to Williamson, though, there was a “strong presumption” that if a claim did not use the words “means for” or “step for,” the claim was not considered a means-plus-function claim (i.e. not subject to § 112, ¶ 6) and the strict requirement of algorithm disclosure did not apply.  Williamson significantly weakened that presumption:

Our consideration of this case has led us to conclude that … we should abandon characterizing as “strong” the presumption that a limitation lacking the word “means” is not subject to § 112, ¶ 6.

Williamson; slip op. at 15.  With that change of law in place, the court found that the claim phrase “a distributed learning control module” was tantamount to “means for” performing a function, and calling it a “nonce word that reflect[s] nothing more than [a] verbal construct…”  Slip op. at 17.  The Court then went on to apply the doctrine of WMS Gaming-Aristocrat-Function Media to find that the claim was indefinite and invalid because the specification failed to disclose an algorithm for performing the claimed function.

What Will Change?

Williamson is an important development in defensive patent litigation practice.  Indefiniteness can be a silver-bullet defense with uniquely appealing strategic elements.  For example, many courts handle indefiniteness simultaneously with claim construction, making available an early dispositive ruling on claim validity in one step. 

Patent plaintiffs are aware of the WMS Gaming/Aristocrat/Function Media cases and typically avoid asserting only claims that are susceptible to such challenges.  But Williamson opens many more claims to scrutiny, and the case may be difficult to avoid for patents that include “functional” limitations across many claims.  Also, defendants in existing patent suits may want to consider whether they can introduce new indefiniteness positions on the basis of Williamson.

Williamson cannot be raised directly in inter partes review or ex parte reexamination proceedings, neither of which allows direct challenges of a patent under § 112.  However, inter partes review proceedings do require the Patent Trial and Appeal Board to construe the claims of a patent.  If the claim cannot be construed (e.g. if it is a means-plus-function term without algorithmic support) the PTAB may decline to review that claim, noting that the claim is indefinite.  While this would result in a denial of post-grant review, such an outcome might have a silver-lining if the written decision would be used to persuade the district court that the patent is indefinite.

For patents that are eligible for Covered Business Method Review, challenges under § 112 are available and Williamson expands their applicability.  CBM petitions do not often include indefiniteness arguments, but those arguments may become more frequent going forward.

The decision will also likely affect prosecution of new patent applications at the USPTO.  Practitioners will want to draft claims to avoid language that could be interpreted as functional, or they will want to include algorithmic support in the specification.  Alternately, practitioners could include some aspects of structure in otherwise functional claim language, to try to “tip the scales” away from finding that the claim is governed by § 112, ¶ 6.