Future Of Means-Plus-Function Claim Interpretation Now Less Clear

The Federal Circuit has weakened the presumption against means-plus-function claim interpretation in its recent en banc decision in Williamson v. Citrix Online, LLC, issued on June 16.

Diverging from a line of precedent dating back to 2002, the majority opinion (written by Judge Richard Linn) held that there is no "strong" presumption that the term "means" is required in the claims to signal that a patent applicant intended interpretation under 35 U.S.C. 112(f) (35 U.S.C. 112 para six, prior to the America Invents Act). That line of Federal Circuit cases established a heightened bar to overcome the presumption against interpreting a functional claim element, which lacked the word "means," as a means-plus-function claim element.