Biosig Instruments, Inc. v. Nautilus, Inc.

Addressing the issue of indefiniteness under 35 U.S.C. 112 ¶2, the U.S. Court of Appeals for the Federal Circuit reversed a summary judgment of indefiniteness regarding the claim term “spaced relationship” and remanded for further proceedings. Biosig Instruments, Inc. v. Nautilus, Inc., Case No. 12-1289 (Fed. Cir., Apr. 26, 2013) (Wallach, J.) (Schall, J., concurring).

Biosig owns a U.S. patent directed to an improved heart rate monitor associated with exercise machines. The patent claimed improvements in heart rate measurements attained by eliminating interfering signals given off by skeletal muscles during exercise (EMG signals). The patent described a cylindrical bar with sensors intended to be gripped by both hands to measure heart signals. The claim in issue recited a live electrode and a common electrode mounted on each end of the cylindrical bar, where the electrodes were in a “spaced relationship with each other.”

Under § 112 ¶2, the scope of the claims must be sufficiently definite to inform the public of the bounds of the protected invention. A claim is indefinite when it is “not amenable to construction” or “insolubly ambiguous.” The district court had construed the term “spaced relationship,” thus the Federal Circuit found that the term was amenable to construction and would be indefinite only if it was insolubly ambiguous.

The Federal Circuit decided a person of ordinary skill would not find the term “spaced relationship” insolubly ambiguous, because the claim language, specification and figures disclosed certain inherent parameters delineating the boundaries of the claim. The Court noted the maximum distance between the live and common electrodes cannot be greater than the width of a user’s hands because the patent required the live and common electrodes to independently detect electrical signals at two distinct points of a hand. Likewise, the distance cannot be so small so as to merge into a single electrode. The Court also faulted the district court’s inquiries into “the size of a user's hands, placement of fingers, and the composition of the handle” as possibly relevant to a enablement inquiry under § 112 ¶1, but not an indefiniteness analysis under § 112 ¶2.

The Federal Circuit found that a “whereby” clause contained in one of the claims described the function of substantially removing EMG signals was “highly relevant” in ascertaining the proper bounds of the claim term, noting the U.S. Patent and Trademark Office (USPTO) had found this function crucial to overcoming prior art during reexamination. When a claim limitation is defined in purely functional terms, determining whether the limitation is sufficiently definite is highly dependent on context. The Court cited evidence in the record showing that those skilled in the art could, with some experimentation, determine the “spaced relationship” between the electrodes that would result in removal of EMG signals.

The Court ultimately held the term “spaced relationship” was not indefinite because it was amenable to construction and because the patent provided inherent parameters sufficient for a skilled artisan to understand the boundaries of the term.

The concurring opinion agreed that the district court erred in its finding of indefiniteness, but faulted the majority analysis for presuming a functional linkage between the “spaced relationship” limitation and the removal of EMG signals.