Federal Circuit applies Nautilus reasonable certainty rule

Managing IP is part of Legal Benchmarking Limited, 1-2 Paris Gardens, London, SE1 8ND

Copyright © Legal Benchmarking Limited and its affiliated companies 2025

Accessibility | Terms of Use | Privacy Policy | Modern Slavery Statement

Federal Circuit applies Nautilus reasonable certainty rule

Biosig’s patent survives despite the earlier setback from the Supreme Court

Yesterday, the Federal Circuit found that Biosig’s patent for a heart rate monitor associated with exercise equipment was not invalid.

The defendant Nautilus had argued that the patent was invalid due to indefiniteness. The case reached the Supreme Court, which rejected the Federal Circuit’s “insolubly ambiguous” test. Justice Ginsburg’s written decision instead provided another test for indefiniteness, stating 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 held that Biosig’s patent was not indefinite even under the new test. Nautilus argued that the term used in the patent referring to “a spaced relationship” between electrodes in the invention is legally indefinite because “the original intrinsic evidence point[s] in two opposite directions, leaving the claims’ boundaries—and thus the potential avenues for follow-on innovation—fundamentally uncertain”.

The Federal Court disagreed. It noted that the Supreme Court’s Nautilus ruling did not hold that terms of degree such as “a spaced relationship” were by definition legally indefinite, just that the patent must provide some standard to measure that degree.

Specifically, it referred back to its previous decision in this case, noting that “an ordinarily skilled artisan would be able to determine this language requires the spaced relationship to be neither infinitesimally small nor greater than the width of a user’s hands”. Furthermore, it said that, looking at the prosecution history, a person skilled in the arts would understand that the spaced relationship “as pertaining to the function of substantially removing EMG signals”, an important part of the invention.

Not so new?

The Federal Circuit also found that despite the Supreme Court directing the lower courts to apply the reasonable certainty standard for indefiniteness, the test is in fact not new. Biosig actually made a similar argument in its briefs and that courts have long held terms such as the ones used in the patent in question to be sufficiently definite. In fact, some observers such as Jason Rantanen of the University of Iowa predicted last month on Patently-O that the test laid out by the Supreme Court in Nautilus would not have much practical effect.

Similarly, Biosig’s counsel argued after the Supreme Court decision that despite the order directing the Federal Circuit to reconsider its patent for indefiniteness, the Supreme Court actually adopted the test that Biosig had argued for.

Judges Newman, Schall, and Wallach sat on the case. Mark David Harris of Proskauer Rose argued for Biosig while John Vandenberg of Klarquist Sparkman represented Nautilus.

more from across site and SHARED ros bottom lb

More from across our site

With the US privacy landscape more fragmented and active than ever and federal legislation stalled, lawyers at Sheppard Mullin explain how states are taking bold steps to define their own regimes
Viji Krishnan of Corsearch unpicks the results of a survey that reveals almost 80% of trademark practitioners believe in a hybrid AI model for trademark clearance and searches
News of Via Licensing Alliance selling its HEVC/VCC pools and a $1.5 million win for Davis Polk were also among the top talking points
The winner of a high-profile bidding war for Warner Bros Discovery may gain a strategic advantage far greater than mere subscriber growth - IP licensing leverage
A vote to be held in 2026 could create Hogan Lovells Cadwalader, a $3.6bn giant with 3,100 lawyers across the Americas, EMEA and Asia Pacific
Varuni Paranavitane of Finnegan and IP counsel Lisa Ribes compare and contrast two recent AI copyright decisions from Germany and the UK
Exclusive in-house data uncovered by Managing IP reveals French firms underperform on providing value equivalent to billing costs and technology use
The new court has drastically changed the German legal market, and the Munich-based firm, with two recent partner hires, is among those responding
Consultation feedback on mediation and arbitration rules and hires for Marks & Clerk and Heuking were also among the major talking points
Nick Groombridge shares how an accidental turn into patent law informed his approach to building a practice based on flexibility and balancing client and practitioner needs
Gift this article