Today the Supreme Court unanimously lowered the bar for proving claim indefiniteness, lowering the barrier for defendants in patent infringement cases to challenge the validity of patent claims on this basis. In Nautilus, Inc. v. Biosig Instruments, Inc., (572 U.S. __) (June 2, 2014), the Court replaced the Federal Circuit’s “insoluble ambiguity” test with a “reasonable certainty” test. Specifically, the Court stated that “we read §112[(b)] to require 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.” Slip Op. at 11.

In seeking cert, petitioner Nautilus asked the Court to adopt a test that would hold a patent claim invalid when it is “ambiguous, such that readers could reasonably interpret the claim’s scope differently.” Id. at 9. Respondent Biosig and the U.S. Solicitor General argued that the claims need only “provide reasonable notice of the scope of the claimed invention.” Id. Ultimately, the Court’s adopted a standard somewhere in between the positions advocated by the parties.

In crafting this new test, the Court acknowledged that the definiteness requirement “must take into account the inherent limitations of language” but at the same time require enough precision “to afford clear notice of what is claimed, thereby apprising the public of what is still open to them.” Id. at 9–10 (internal quotations omitted). The “reasonable certainty” test is the Court’s attempt to “reconcile concerns that tug in opposite directions” and “mandate[] clarity, while recognizing that absolute precision is unattainable.” Id. at 11.

The Court reasoned that it was replacing the “insoluble ambiguity” test because it is imprecise in application, and serves to diminish the public-notice function of patents. The Court explained that claims upheld under the former test would “breed lower court confusion, for they lack the precision §112[(b)] demands.” Id. at 11–12. Further, “[t]o tolerate imprecision just short of that rending 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.” Id. at 12.

The Supreme Court’s opinion in Nautilus represents yet another effort by the Court to hold patent owners to a higher standard when seeking to enforce their rights. Practitioners should pay attention to how this new test plays out in the U.S. Patent Office and in the district courts, as the decision could affect both prosecution and litigation alike. The Federal Circuit is sure to provide some guidance, as the Supreme Court remanded this case for further consideration in light of the new standard.