In yet another rejection of prevailing norms for determining patent validity, the U.S. Supreme Court refined the standard by which courts assess the clarity of patent claims.  Until now, a patent claim was deemed insufficiently clear, and therefore invalid for indefiniteness, only if a court found the claim language to be “insolubly ambiguous.”

In its June 2 decision in Nautilus, Inc. v. Biosig Instruments, Inc., the Court held that a patent is invalid for indefiniteness if its claims fail to define the scope of the invention with “reasonable certainty.”  This lower standard will make patent claims easier to invalidate and portends a surge of indefiniteness defenses in patent litigation.

A patent is a property right that allows the owner to exclude others from using an invention and, “like any property right, its boundaries should be clear.”  To that end, U.S. patent law requires that a patent include “claims particularly pointing out and distinctly claiming the subject matter” that the inventor regards as the invention.  A claim that does not meet these criteria fails to meet the law’s “public-notice function” because it fails to define the scope of the patent owner’s right to exclude, and is therefore invalid for being indefinite.

However, the courts have recognized that written language is an imperfect tool.  The limits of written language are sometimes evident in patent claims that, by definition, describe a new invention, something that has never previously been described.  Fittingly, courts have acknowledged that absolute precision in patent claims is unattainable.  The issue in Nautilus focused on “just how much imprecision [the law] tolerates.”

Biosig patented a monitor useful for measuring a person’s heart rate while exercising, for example, on a treadmill.  Such measurements are challenging because it is difficult to distinguish the electrical signal produced by the heart (an “ECG” signal) from electrical signals produced by other hard-working muscles (“EMG” signals).

Biosig realized that a user’s heart signal appears differently at the user’s left hand than at the user’s right hand, while muscle signals appear the same way at both hands.  Biosig capitalized on this discovery by developing a circuit that measures the heart and muscle signals at both hands using two pairs of electrodes – one pair for each of the user’s hands.  The patented Biosig circuit subtracts one of the measurements from the other to cancel out the muscle signals and leaves only the heart signal.

Biosig’s patent claims required that each pair of electrodes include a “live electrode” and a “common electrode” and that the live electrode and common electrode be “in a spaced relationship with each other.”

Biosig accused Nautilus, through its StairMaster line of exercise products, of infringing the Biosig patent.  But Nautilus convinced the trial court that the term “spaced relationship” was fatally indefinite because Biosig did not disclose “what precisely the space should be” or even provide parameters “for determining the appropriate spacing.”

The Court of Appeals for the Federal Circuit reversed the trial court’s decision.  That court had customarily held that a claim is indefinite only when it is “not amenable to construction” or is “insolubly ambiguous.”  The Federal Circuit upheld the validity of the Biosig claims because it found that the claims were not “insolubly ambiguous.”  Nautilus appealed to the U.S. Supreme Court.

The Supreme Court found fault in both the form and substance of the “insolubly ambiguous” standard.  In an ironic twist, the Supreme Court found that the phrase “insolubly ambiguous” is itself unacceptably indefinite.  Although the Court claims not to “micromanage” the Federal Circuit’s choice of words, it found that the lower court’s “terminology can leave courts and the patent bar at sea without a reliable compass.”

As for substance, the Court disparaged the “insolubly ambiguous” standard per se: “To tolerate imprecision just short of that rendering a claim ‘insolubly ambiguous’ would diminish the definiteness requirement’s public-notice function and foster the innovation-discouraging ‘zone of uncertainty’ against which this Court has warned.”

To its credit, Nautilus had convinced the Supreme Court that the Federal Circuit’s “insolubly ambiguous” standard failed to provide the courts with appropriate guidance in determining whether a patent claim is indefinite.

However, Nautilus failed to convince the Court to adopt a much lower standard whereby a claim would be indefinite and invalid merely if “readers could reasonably interpret the claim’s scope differently.”  Nautilus’s proposed threshold was simply too low for the Supreme Court, because “some modicum of uncertainty is the ‘price of ensuring the appropriate incentives for innovation.’”

Rather, the Court cited its 1902 decision in Carnegie Steel Co. v. Cambria Iron Co. for the proposition that “any description which is sufficient to apprise [steel manufacturers] in the language of the art of the definite feature of the invention, and to serve as a warning to others of what the patent claims as a monopoly, is sufficiently definite to sustain the patent.”

Ultimately, the Court held that “a patent is invalid for indefiniteness if its claims, read in light of the specification delineating the patent, and the prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.”

The Supreme Court declined to apply its revised standard to the facts in the Nautilus case, and instead remanded the case with instructions that the Federal Circuit reconsider whether the Biosig claims are indefinite.

Nevertheless, Nautilus should induce patent drafters to avoid drafting patent applications with vague claims–indeed, the court expressly says that “the patent drafter is in the best position to resolve the ambiguity”– and help the public understand the proper scope of an issued patent’s right to exclude.

As a practical matter, the decision reinforces the need for inventors to educate their patent attorneys about all pertinent aspects of their inventions.  Armed with that information, attorneys are better positioned to draft comprehensive patent applications that provide a solid foundation for broad claim scope.

For patent attorneys, Nautilus highlights the value of drafting a range of claims, from the broadest claims supported by the text and figures of the application, to narrower, more easily defendable claims.  The broadest claims provide the greatest scope of protection for the invention, and allow for broad assertion of infringement, while the narrower claims provide strong fallback positions. Taken together, these approaches operate to increase the value of the patent asset.