In an opinion addressing the standard for indefiniteness in view of the Supreme Court of the United States’ 2014 “reasonable certainty” test, the U.S. Court of Appeals for the Federal Circuit maintained its reversal of the district court’s determination that the asserted claims were indefinite. Biosig Instruments, Inc. v. Nautilus, Inc., Case No. 12-1289 (Fed. Cir., Apr. 27, 2015) (Wallach, J.)

Biosig sued Nautilus for patent infringement. The asserted patent is directed to a heart rate monitor that processes signals from which electromyogram (EMG) signals are substantially removed. Notably, certain asserted claims recite common and live electrodes being in “spaced relationship” with each other. The district court granted Nautilus’s motion for summary judgment, holding the “spaced relationship” term indefinite as a matter of law. Biosig appealed.

On appeal, the Federal Circuit reversed and remanded. The majority, relying on a standard articulated in the 2005 Datamize case, stated that a claim is indefinite “only when it is ‘not amenable to construction’ or ‘insolubly ambiguous.’” The Federal Circuit panel majority found that the claims at issue were not indefinite because the claim language, specification and figures disclosed certain inherent parameters delineating the boundaries of the claims.

The Supreme Court granted certiorari , and vacated and remanded. In so doing, the Supreme Court rejected the Federal Circuit’s “not amenable to construction or insolubly ambiguous” standard, and articulated a new standard to be applied: “[W]e 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.”

On remand, the Federal Circuit first addressed whether the Supreme Court had raised the standard for indefiniteness or had simply clarified the existing standard. The Federal Circuit noted that the Supreme Court had reframed the inquiry as an affirmative search for “reasonable certainty” rather than a rejection of insolubly ambiguous claims or those not amenable to construction. 

Using the modified standard, the Federal Circuit found that the “spaced relationship” claim language informed skilled artisans with reasonable certainty regarding its scope. The Federal Circuit reaffirmed that the intrinsic evidence allowed a skilled artisan to determine the parameters of the claims. First, the common and live electrodes need to be separated from one another, and yet the distance between the two cannot be wider than the width of a user’s hands. Second, the claims include a whereby clause describing the spared electrode structure as functioning to substantially remove EMG signals. In the Federal Circuit’s view, the recitation of this function proved crucial, as a skilled artisan would understand the boundaries of the “spaced relationship” between the common and live electrodes based on the substantial removal of the EMG signals.