On June 2, 2014, the U.S. Supreme Court issued an important decision regarding the standard to determine whether claims are indefinite. In Nautilus, Inc. v. Biosig Instruments, Inc., No. 13-369, the Court held that the current Federal Circuit threshold requiring only that a claim be “amenable to construction” and not “insolubly ambiguous” was insufficient to satisfy the definiteness requirement of 35 U.S.C. § 112. Rather, a “reasonable certainty” standard was articulated for claim definiteness: “In place of the ‘insolubly ambiguous’ standard, we hold that 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.” Nautilus, slip op. at 1. The Court’s holding has implications in analyzing whether an inventor has presented claims that particularly point out and distinctly claim the invention, as required by statute.

In the decision on review, the Federal Circuit had found that the challenged claims of U.S. Patent No. 5,337,753 (“the ’753 patent”) were not indefinite. The claims at issue were directed to a heart-rate monitor contained in a hollow cylindrical bar that a user could grasp during exercise, thereby contacting two electrodes. Id. at 4. Claim 1 contained a limitation describing the electrodes as being “mounted . . . in spaced relationship with each other.” Id. (citation omitted). According to Biosig, this “spaced relationship” referred to “the distance between the live electrode and the common electrode in each electrode pair.” Id. at 6. Nautilus maintained that the “spaced relationship” must be a distance “greater than the width of each electrode,” or else the claims would be open to multiple interpretations reflecting vastly different understandings of the ’753 patent’s scope. Id. (citation omitted). The majority opinion at the Federal Circuit held that a claim is indefinite “only when it is ‘not amenable to construction’ or ‘insolubly ambiguous.’” Biosig Instruments, Inc. v. Nautilus, Inc., 715 F.3d 891, 898 (Fed. Cir. 2013) (citation omitted). The Federal Circuit found that, under this standard, the claim was not indefinite. Id

Justice Ginsburg, writing for the unanimous court, noted several initial points that were not in dispute. First, definiteness is to be evaluated from the perspective of someone of ordinary skill in the art. Nautilus, slip op. at 8. This squares with the practice elsewhere under 35 U.S.C. § 112. See id. Second, claims are read in light of the specification and prosecution history. Id. And third, definiteness is measured at the time of filing. Id. at 9. Notwithstanding this common understanding, the disputed issue in the case was precisely how much imprecision in claiming does § 112, ¶ 2 (section 112(b) under the America Invents Act amendments) tolerate before a claim is rendered invalid.

The answer, according to the Court, requires a “delicate balance.” Id. On the one hand, the Court recognized that some degree of uncertainty was inevitable because of the inherent limitations of language. See id. But the public notice function of patents, on the other hand, requires clear notice of what is claimed and what is still open for use. See id. at 10. Tension between these two concepts led the Court to promulgate a flexible “reasonableness” test, as it has done elsewhere in the patent law:

Cognizant of the competing concerns, we read §112, ¶2 to require that a patent’s claims, viewed in light of the specification and prosecution history, inform those skilled in the art about the scope of the invention with reasonable certainty. The definiteness requirement, so understood, mandates clarity, while recognizing that absolute precision is unattainable.

Id. at 11 (quoting Minerals Separation, Ltd. v. Hyde, 242 U.S. 261, 270 (1916) (“[T]he certainty which the law requires in patents is not greater than is reasonable, having regard to their subject matter.”)). The ability to ascribe at least some meaning to a claim term, continued the Court, does not meet the statutory test for precision; rather, “the definiteness inquiry trains on the understanding of the skilled artisan at the time of the patent application . . . .” Id. at 12. 

The Supreme Court rejected the Federal Circuit’s formulation of the definiteness test as “breed[ing] lower court confusion.” Id. at 11-12. Although the Court acknowledged that the actual analysis performed by the Federal Circuit was actually closer to tracking the statute’s requirements than the “insolubly ambiguous” and “amenable to construction” shorthand suggested, the Court was nevertheless concerned that such loose terminology could leave the patent bar without adequate guidance on this issue. Id. at 12-13. The Supreme Court remanded the case for consideration of the claim term “spaced relationship” using a test consistent with its opinion.

Practitioners should be aware that the courts will now look through a new lens to determine definiteness. The Nautilus test for definiteness focuses on the perspective of one skilled in the art at the time of application to determine whether there is sufficiently distinct claiming to reasonably inform those skilled in the art about the scope of the invention. The Nautilus opinion was clearly concerned about preventing patent drafters from intentionally injecting ambiguity into claims. See id. at 10-11. Thus, patent applicants should carefully consider the Nautilus opinion when choosing claim language to define their inventions.