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Nautilus, Inc., v. Biosig Instruments, Inc.

United States Supreme Court
134 S. Ct. 2120 (2014)



Biosig Instruments, Inc. (Biosig) (plaintiff) owned a patent for a heart-rate monitor. The heart-rate monitor could be used on exercise equipment. The monitor consisted of a cylindrical bar that an exerciser had to grip with both hands. Two electrodes within the bar picked up the electrical signals from the user to provide information about the user’s heart rate. The patent’s claim stated that the two electrodes had to be mounted “in spaced relationship with each other.” Biosig shared this heart-monitor technology with StairMaster Sports Medical Products, Inc. (StairMaster). StairMaster began selling products incorporating the technology. Nautilus, Inc. (Nautilus) (defendant) acquired StairMaster and continued selling products using the heart-monitor technology. Biosig sued Nautilus for patent infringement. Nautilus argued that Biosig’s patent was invalid because Biosig’s claims lacked definiteness. Specifically, the patent’s description of the electrodes’ spacing was insufficiently definite. The district court granted Nautilus’s motion. Biosig appealed. The Federal Circuit Court of Appeals reversed, holding that a claim’s written description is indefinite only if it is not amenable to construction or insolubly ambiguous. Given other details supplied in Biosig’s patent’s specification, the proper spacing of the invention’s electrodes could be understood to be within certain parameters. Therefore, Biosig’s patent was not insolubly ambiguous. Nautilus petitioned the United States Supreme Court for certiorari. The dispute before the Supreme Court was about how imprecise a patent can be before it fails the definiteness requirement. Biosig claimed that as long as a patent’s claim provided notice of the invention, then that was sufficiently definite. Nautilus argued that if two people could read a claim differently, then the claim was ambiguous and indefinite and, therefore, invalid.

Rule of Law


Holding and Reasoning (Ginsburg, J.)

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