Biosig Instruments, Inc. v. Nautilus, Inc.

Biosig Instruments, Inc. (Biosig) (plaintiff) held a patent for a heart-rate monitor to be used on exercise equipment. The monitor calculated a user’s heart rate via electrodes on a cylindrical bar on which a user’s hands would be placed during exercise. The patent’s claims described the invention as requiring two pairs of electrodes, with each pair having a live electrode and a common electrode. The claims stated that the live electrode and the common electrode were to be “in spaced relationship” with each other. When Biosig sued Nautilus, Inc. (defendant) for patent infringement, Nautilus moved for summary judgment, arguing that the patent claims were invalid for indefiniteness because the term “spaced relationship” was not sufficiently particular to satisfy patent law’s definiteness requirement. Biosig argued that although the patent did not define the term “spaced relationship,” an ordinary person in the field would understand that the space between the live and common electrodes must not be infinitesimally small and must not be greater than the width of a user’s hand. Biosig also argued that such spacing was discernable from figures in the patent that showed the electrodes to be approximately hand’s-width apart. The district court granted summary judgment in Nautilus’s favor, finding the patent claims were invalid for indefiniteness. The Federal Circuit reversed, concluding that the patent claims were sufficiently definite because they were amenable to construction and were not insolubly ambiguous. The Supreme Court granted review and announced a different standard for assessing definiteness. It remanded the case to the Federal Circuit for application of that standard.