The patent laws require that the claims of a patent (which define the boundaries of what the patent owner can protect) “particularly point out and distinctly claim the subject matter … of the invention.”  35 U.S.C. §112, ¶2.  This requirement is referred to as “definiteness.”  A patent that fails to satisfy this requirement may be found to be invalid for indefiniteness.

The purpose of the definiteness requirement is to provide the public with notice of what the patent owner owns, and what would be an infringement of the patent.  Thus, the definiteness requirement serves to encourage innovation by providing certainty as to what the patent protects.

This year, the United States Supreme Court vacated a Federal Circuit Court of Appeals decision on the grounds that the Federal Circuit’s test for indefiniteness was not precise enough and would result in confusion in the district courts.  The case is Nautilus, Inc. v. Biosig Instruments, Inc., 189 L.Ed. 2d 37 (June 2, 2014).

In 2004, the patent owner, Biosig, sued Nautilus for infringement of a patent covering a heart-rate monitor used in exercise.  Biosig’s heart monitor was different from existing heart monitors in that it was more accurate because it did not measure both electrical signals from the user’s heart and from the muscles.  The Biosig heart monitor used two pairs of electrodes, one pair for each hand of the user.  Biosig alleged that Nautilus, who owned the StairMaster brand of exercise machine, used the patented heart monitor in StairMaster machines.
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