In Williamson v. Citrix Online, LLC, No. 2013-1130 (Fed. Cir., June 16, 2015), the Federal Circuit, sitting en banc, overruled earlier opinions and held that the absence of the word “means” does not justify a “strong” presumption that a claim limitation is not subject to section 112, para. 6. It also held that a party seeking to apply section 112, para. 6 was not required to demonstrate “that the limitation essentially is devoid of anything that can be construed as structure.” This decision is a significant change in the law, and should be taken into account in litigation and in patent application drafting.

The Williamson decision essentially reverts back to the standard adopted in Personalized Media Communications, LLC v. International Trade Commission, 161 F.3d 696, 703-04 (Fed. Cir. 1998). In that case, the court held that the use of the word “means” in a claim element creates a rebuttable presumption that section 112, para. 6 applies, and, conversely, that the failure to use the word “means” also creates a rebuttable presumption—this time that section 112, para. 6 does not apply.