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Supreme Court Sets Forth New Standard for Indefiniteness, Requiring Greater Precision in Claim Terms than the Standard Long Used by Federal Circuit

For over a decade, to show that a claim term is invalid as indefinite under 35 U.S.C. §112, ¶2, the Federal Circuit has required that such terms be “not amenable to construction” or “insolubly ambiguous.” The Supreme Court in Nautilus, Inc. v. Biosig Instruments, Inc. has rejected that standard on the grounds that it tolerates too much imprecision. Under the new standard, a claim term is indefinite if it, instead, fails to define “the scope of the invention with reasonable certainty.”

The patent at issue, assigned to Biosig Instruments, Inc. (“Biosig”), involves a heart-rate monitor used with exercise equipment. Prior heart-rate monitors, the patent asserts, were often inaccurate in measuring the electrical signals accompanying each heartbeat (electrocardiograph or ECG signals) because of the presence of other electrical signals (electromyogram or EMG signals) generated by the user’s skeletal muscles. The invention claims to improve on prior art by detecting and processing ECG signals in a way that filters out the EMG interference.

Claim 1 of the patent, which contains the limitations critical to the case, recites a “heart rate monitor for use by a user in association with exercise apparatus and/or exercise procedures.” The claim comprises, among other elements, a cylindrical bar with a “live” electrode and a “common” electrode “mounted . . . in spaced relationship with each other.” Biosig filed the underlying patent infringement suit, alleging that Nautilus, Inc. (“Nautilus”) infringed on its patented claims by selling exercise machines containing Biosig’s patented technology.

After conducting a claim construction hearing, the district court granted Nautilus’s motion for summary judgment on the ground that the claim term “in spaced relationship with each other” failed the definiteness requirement. The Federal Circuit reversed and remanded, concluding that a patent claim passes the §112, ¶2 threshold so long as the claim is “amenable to construction,” and the claim, as construed, is not “insolubly ambiguous.” Under that standard, the court determined, the ‘753 patent survived indefiniteness review.

The Supreme Court disagreed and rejected the Federal Circuit’s test for indefiniteness. According to the Supreme Court, a proper reading of §112, ¶2 requires that a patent be held invalid for indefiniteness if its claims, read in light of the patent’s specification and prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.

The Court began its analysis by setting forth the aspects of the §112, ¶2 inquiry on which all parties agreed. The parties agreed that definiteness is to be evaluated from the perspective of a person skilled in the relevant art, that claims are to be read in light of the patent’s specification and prosecution history, and that definiteness is to be measured as of the time of the patent application.

The parties disagreed, however, as to how much imprecision §112, ¶2 tolerates. That issue, the Court admitted, is a delicate one. According to the Court, the definiteness requirement must take into account the inherent limitations of language. On the one hand, some modicum of uncertainty is the “price of ensuring the appropriate incentives for innovation.” On the other hand, a patent must be precise enough to afford clear notice of what is claimed, thereby apprising the public of what is still open to them in a manner that avoids a “zone of uncertainty which enterprise and experimentation may enter only at the risk of infringement claims.” In the Court’s view, the standard adopted by the Court mandates clarity, while recognizing that absolute precision is unattainable.

The Federal Circuit’s standard, on the other hand, lacks the precision §112, ¶2 demands. To tolerate imprecision just short of that rendering a claim “insolubly ambiguous” would diminish the definiteness requirement’s public-notice function and foster the innovation-discouraging “zone of uncertainty.” More specifically, the expressions “insolubly ambiguous” and “amenable to construction,” which permeate the Federal Circuit’s recent decisions concerning §112, ¶2, can leave courts and the patent bar at sea without a reliable compass. While some of the Federal Circuit’s fuller explications of the term “insolubly ambiguous” may come closer to tracking the statutory prescription, the Court held that it must set forth the correct standard to ensure that the Federal Circuit’s test is at least “probative of the essential inquiry.”