In Dow Chemical Co. v. Nova Chemicals Corp., 803 F.3d 620 (Fed. Cir. 2015), the Federal Circuit directly acknowledged that the Supreme Court’s recent ruling in Nautilus, Inc. v. Biosig Instruments, Inc., 134 S. Ct. 2120 (2014) changed its standard for definiteness under 35 U.S.C. 112. This decision is important because it distinguishes a prior suggestion in Biosig v. Nautilus, 783 F.3d 1374 (Fed. Cir. 2015) that Nautilus had no practical effect, but just reworded a “familiar standard.”[1] This decision continues a trend towards stricter requirements for definite claim scope.

The Federal Circuit panel stated, in no uncertain terms, that “there can be no serious question that Nautilus changed the law of indefiniteness.”[2] The Supreme Court held that the prior standard for indefiniteness—whether a claim is amenable for construction or insolubly ambiguous—was contrary to the requirements of 35 U.S.C. 112. Under the new standard, “a patent is invalid for indefiniteness if its claims, read in light of the specification delineating the patent, and the prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.”[3]

The Court pointed out that that under the old standard, the claims were definite.[4] Under the Nautilus standard, they are now indefinite.[5] Nautilus amounts an “intervening change in law.”[6]

The claims in Dow required measuring a slope of strain hardening coefficient, but three methods existed to determine the maximum slope.[7] Each method was “simply a different way of determining the maximum slope.”[8] The patentee’s expert developed a fourth method that was used to analyze the accused product. All four methods could produce different coefficients. And the “claims, specification, and prosecution history” provided no guidance on which method must be used.[9] “[T]he existence of multiple methods lead[s] to different results without guidance in the patent or the prosecution history as to which method should be used renders the claims indefinite.”[10]

Practitioners should take note of a trend that is breathing new life into the definiteness requirements 35 U.S.C. 112. The Dow decision reemphasized that a claim term is indefinite under 112(b) if it “leave[s] the skilled artisan to consult the ‘unpredictable vagaries of any one person’s opinion’” to determine claim scope.[11] In Williamson v. Citrix, 792 F.3d 1339 (2015), the Federal Circuit reemphasized that the restrictions of 112(f) may apply even when “means” or “step” is not used when claiming in functional, rather than structural, terms. The trend exhibited by Dow and Williamson may have particular impact on software patents, where ill-defined, coined claim terms and functional claiming for intangible concepts have appeared over the past two decades with increasing frequency.