The recent trend of the U.S. Supreme Court overturning the nation’s patent appeal court continued with the Nautilus decision. In Nautilus, the Supreme Court threw out the Federal Circuit’s “insolubly ambiguous” standard for determining whether claims are invalid for indefiniteness.

Under 35 U.S.C. § 112 ¶ 2, patent claims must “particularly point[] out and distinctly claim[] the subject matter which the inventor or a joint inventor regards as the invention.” This is referred to as the “definiteness” standard. A claim that fails to satisfy the definiteness standard is invalid and may not be enforced.

The Federal Circuit has held that claims are indefinite under § 112 ¶ 2 when they are “not amenable to construction” or are “insolubly ambiguous.” In 2013, the Federal Circuit applied this standard in the case of Biosig Instruments, Inc. v. Nautilus, Inc.  The claim at issue in Nautilus concerned a heart rate monitor for exercise equipment that used two electrodes in a “spaced relationship” with each other. In prior ex parte reexamination proceedings, the patent owner argued that the “spaced relationship” was a key limitation that distinguished the claimed invention from dual-electrode monitors found in the prior art. In the District Court proceedings, however, the patent owner argued that a “spaced relationship” could be any “defined relationship” between the electrodes. Based on that construction, the U.S. District Court for the Southern District of New York found that the “spaced relationship” limitation was indefinite under § 112 ¶ 2 because it would not disclose the bounds of the claimed invention to someone of skill in the art. The Federal Circuit reversed, holding that it was possible to assign a meaning to “spaced relationship” and therefore the limitation was not indefinite. In particular, the Federal Circuit held that the “spaced relationship” would necessarily be close enough so that the electrodes could fit within a person’s hand. The Federal Circuit also noted that a person of skill in the art could perform testing to determine the ideal spaced relationship.

In a unanimous decision delivered by Justice Ginsburg, the Supreme Court rejected the “insolubly ambiguous” and “amenable to construction” tests that the Federal Circuit applied in Biosig. The Court noted that those standards “lack the precision that § 112 ¶ 2 demands” and therefore “can breed lower court confusion.” The Court also explained that “[i]t cannot be sufficient [under § 112 ¶ 2] that a court can ascribe some meaning to a patent’s claims.” Instead, the Court held that § 112 ¶ 2 “require[s] that a patent’s claims, viewed in light of the specification and prosecution history, inform those skilled in the art about the scope of the invention with reasonable certainty.”  The Court noted that this standard “mandates clarity, while recognizing that absolute precision is unattainable.”

The Supreme Court declined to determine whether the underlying “spaced relationship” limitation at issue in Nautilus satisfied the newly articulated standard. Instead, the Court remanded the case so that the Federal Circuit could determine whether a person of skill in the art would have understood the scope of the invention with “reasonable certainty.” Given the new standard, it is likely that patent defendants will more frequently seek to invalidate patents using the lower indefiniteness standard.