In Biosig Instruments, Inc. v. Nautilus, Inc., the Federal Circuit reversed a decision by the U.S. District Court for the Southern District of New York finding a patent invalid for indefiniteness, relying on intrinsic evidence. Biosig Instruments, Inc. (“Biosig”) is the assignee of U.S. Patent No. 5,337,753 (“the ’753 patent”). The ’753 patent is directed to a heart rate monitor for use with exercise equipment and exercise procedures. Biosig sued Nautilus, Inc. (“Nautilus”) for patent infringement alleging that claims 1 and 11 of the ’753 patent were infringed by Nautilus’s exercise equipment that has a mounted heart rate monitor.
In the late 1990s, Biosig was in negotiations with Stairmaster Company—Nautilus’s predecessor—regarding Biosig’s patented technology, but the companies failed to reach an agreement. Stairmaster, and eventually Nautilus, started to sell exercise equipment with mounted heart rate monitors. Biosig sued Nautilus in August 2004, alleging that the equipment infringed its patent. Following reexaminations and re-filed patent infringement suits, the District Court for the Southern District of New York eventually conducted a Markman hearing on the asserted claims of the ’753 patent in September 2011. Among the terms the court construed was the term “spaced relationship.” The district court construed the term to mean that “there is a defined relationship between the live electrode and the common electrode on one side of the cylindrical bar and the same or a different defined relationship between the live electrode and the common electrode on the other side of the cylindrical bar.” Following the district court’s claim construction, Nautilus moved for summary judgment of non-infringement and invalidity for indefiniteness.
In February 2012, the district court ruled on the summary judgment motions, denying the motion for summary judgment of non-infringement and granting the motion for invalidity based on indefiniteness. The district court’s holding of invalidity for indefiniteness was founded on the conclusion that the term “spaced relationship” was ambiguous, despite the fact that the court had construed the term in its Markman order. Biosig appealed the district court’s grant of summary judgment, with the sole issue on appeal being the indefiniteness of “spaced relationship.”
On appeal, the Federal Circuit’s analysis began with a summary of the standards of indefiniteness, stating “[a] claim is indefinite only when it is ‘not amenable to construction’ or ‘insolubly ambiguous.’” The Court went on to discuss words of degree, for which “the court must determine whether the patent provides ‘some standard for measuring that degree.’” In this instance, the Court concluded that the term was not indefinite, as it “was amenable to construction,” whereas “indefiniteness . . . would require a showing that a person of ordinary skill would find ‘spaced relationship’ to be insolubly ambiguous—that it fails to provide sufficient clarity delineating the bounds of the claim to one skilled in the art.” The Federal Circuit specifically relied on the intrinsic evidence that the district court used in construing the term in its Markman order. In doing so, the Federal Circuit noted that the specification described the “spaced relationship” of the electrodes in terms of their function, and cited the evidence submitted during the reexamination, including a declaration by the inventor, used to traverse a rejection by the USPTO. In light of the specification and intrinsic evidence, the Federal Circuit held that the term “spaced relationship” was not indefinite; and therefore, that the grant of summary judgment was in error. Accordingly, the Federal Circuit reversed the district court’s invalidity determination and remanded the case for further proceedings.