What Do You Mean? Nautilus Ruling Holds That a Patent Claim Must Convey with Reasonable Certainty the Scope of the Invention


On June 2, a unanimous U.S. Supreme Court held in Nautilus Inc. v. Biosig Instruments Inc. that a patent claim may be found indefinite if it fails to convey the scope of the invention “with reasonable certainty” to a person skilled in the art. No. 13-369, 2014 WL 2440536 (U.S. June 2, 2014). In doing so, the U.S. Supreme Court rejected the U.S. Court of Appeals for the Federal Circuit’s previous ruling that a patent claim is definite so long as the claim is “amenable to construction” and not “insolubly ambiguous.”

Assigned to Biosig, the patent at issue (U.S. Patent No. 5,337,753) involves a grip-activated heart-rate monitor used with exercise equipment. In particular, the patent describes a heart-rate monitor contained in a hollow cylindrical bar that a user grips with both hands, such that each hand comes into contact with two electrodes. Claim 1 of the patent includes the additional limitation that the electrodes are “mounted . . . in spaced relationship with each other.”

Biosig alleged that Nautilus sold exercise machines containing Biosig’s patented technology. The District Court, after conducting a hearing to determine the proper construction of the patent’s claims, granted Nautilus’ motion for summary judgment on the ground that the claim term “in spaced relationship with each other” was indefinite. Nautilus, 2014 WL 2440536, at *4. The Federal Circuit reversed and remanded, concluding that a patent claim is definite so long as the claim is “amenable to construction,” and the claim is not “insolubly ambiguous.” See Biosig Instruments, Inc. v. Nautilus, Inc., 715 F.3d 891, 898 (Fed. Cir. 2013). Under that standard, the Federal Circuit determined that the term “in spaced relationship” survived an indefiniteness review. Id.

The Supreme Court took issue with the Federal Circuit’s indefiniteness standard. Specifically, the Supreme Court noted that the Federal Circuit’s indefiniteness standard tolerates some ambiguous claims but not others. Nautilus, 2014 WL 2440536, at *8. The Supreme Court also noted that the current standard fosters uncertainty, which can leave courts and the patent bar at sea without a reliable compass. Id. In light these shortcomings, the Supreme Court went on to change the standard for determining indefiniteness, holding that a patent is invalid for indefiniteness if its claims, read in light of the patent’s specification and prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention. Id

In short, by lowering the standard for determining if a patent claim is indefinite, the U.S. Supreme Court’s decision in Nautilus Inc. v. Biosig Instruments Inc. makes it easier for alleged infringers to invalidate patents for being overly vague. The old standard incentivized patentees to inject ambiguity into their claims. The new standard should provide a brighter line to potential infringers on what is covered by a patent claim and what is not.


DISCLAIMER: Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations.

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