## Facts

- Biosig Instruments owned U.S. Patent No. 5,337,753, claiming a heart-rate monitor for exercise equipment designed to reduce noise from skeletal muscle signals while detecting ECG signals.
- The disputed claim language described electrodes “mounted . . . in spaced relationship with each other” on an exercise-machine bar.
- Biosig sued Nautilus for infringing claims 1 and 11 of the patent.
- The district court granted summary judgment to Nautilus, holding the claims invalid for indefiniteness because the spacing term did not specify parameters that would set clear claim boundaries.
- The Federal Circuit reversed, applying its “amenable to construction” / “insolubly ambiguous” standard and concluding the spacing limitation could be understood in context.
- The Supreme Court granted certiorari to determine the correct indefiniteness standard under 35 U.S.C. § 112 ¶ 2.

## Issues

1. What is the proper standard for invalidating a patent claim as “indefinite” under 35 U.S.C. § 112 ¶ 2’s requirement that claims “particularly point[] out and distinctly claim[]” the invention?
2. Whether the Federal Circuit’s “insolubly ambiguous” approach is consistent with § 112 ¶ 2’s definiteness requirement.

## Decision

- The Supreme Court unanimously rejected the Federal Circuit’s “insolubly ambiguous” formulation as too permissive.
- The Court held that a claim is invalid for indefiniteness if, read in light of the specification and prosecution history, it fails to inform those skilled in the art of the invention’s scope with reasonable certainty.
- The Court vacated the Federal Circuit’s judgment and remanded for reconsideration under the “reasonable certainty” standard.
- The Court did not decide whether the specific claims at issue were definite under the new standard.

## Legal Principles

- Definiteness under § 112 ¶ 2 requires that claims, considered with the intrinsic record, provide reasonably certain notice of the scope of the invention to persons skilled in the art at the time of filing.
- The definiteness requirement serves a public-notice function by enabling competitors to determine what is protected, avoid infringement, and design around the patent.
- Absolute precision is not required, but tolerating imprecision up to the point of “insoluble ambiguity” creates an impermissible zone of uncertainty.
- The presumption of validity does not lower the substantive definiteness standard; it concerns the evidentiary burden for proving invalidity.

## Conclusion

The Supreme Court tightened the indefiniteness standard, holding that patent claims must, in view of the specification and prosecution history, inform skilled artisans with reasonable certainty about the invention’s scope, and it remanded for application of that standard to the disputed claims.


Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898 (2014)