## Facts

- U.S. Patent No. 4,128,357 (the “Barth patent”) claims a concrete paving stone of a specified shape and proportions intended to provide interlocking strength while producing a visually symmetric surface pattern from an individual stone that is not itself symmetric.
- Demaco Corporation manufactured and sold paving products that led to a dispute with F. Von Langsdorff Licensing Limited and F. Von Langsdorff Bauverfahren GmbH (together, “Langsdorff”), who asserted rights under the Barth patent.
- Demaco filed a declaratory-judgment action in the Middle District of Florida seeking declarations of noninfringement and invalidity and challenging enforceability; Langsdorff asserted infringement by counterclaim and involved certain Demaco customers/distributors.
- The district court held claims 9, 13, and 29–33 invalid for obviousness under 35 U.S.C. § 103, found all claims unenforceable for inequitable conduct during prosecution, and entered a judgment of no infringement based on those rulings.
- On obviousness, the district court characterized the claimed stone as a simple design and found no clear structural advantage over prior paving-stone configurations.
- Langsdorff presented objective evidence bearing on nonobviousness, including commercial success and marketplace acceptance of stones practicing the patent; the dispute included whether that evidence was sufficiently connected to the claimed features rather than to other causes.
- On inequitable conduct, the district court found misconduct based on alleged failures in disclosure and/or characterization of prior art during prosecution; the appeal focused on whether the record supported both materiality and a specific intent to mislead the USPTO.
- Langsdorff appealed to the Federal Circuit from the adverse judgment.

## Issues

1. Whether the district court erred in holding claims 9, 13, and 29–33 of the Barth patent invalid as obvious under 35 U.S.C. § 103 in view of the prior art and the objective evidence of nonobviousness.
2. Whether the district court erred in holding all claims unenforceable for inequitable conduct absent clear and convincing proof of both materiality and specific intent to deceive the USPTO.
3. Whether the resulting judgment of no infringement could stand after review of the invalidity and unenforceability rulings.

## Decision

- The Federal Circuit reversed the district court’s judgment that claims 9, 13, and 29–33 were invalid for obviousness.
- The Federal Circuit reversed the finding of inequitable conduct and the resulting ruling that the patent was unenforceable.
- Because the district court’s no-infringement judgment rested on the invalidity and unenforceability determinations, the Federal Circuit reversed that disposition and remanded for further proceedings consistent with its opinion.

## Legal Principles

- Obviousness under § 103 is assessed under the Graham framework: the scope and content of the prior art, differences between the prior art and the claims, level of ordinary skill, and objective evidence bearing on nonobviousness.
- Objective evidence such as commercial success, copying, and industry acceptance is part of the obviousness analysis and must be considered on the record; obviousness is not established merely by labeling the invention “simple” in hindsight.
- Commercial success has probative value only when there is a legally sufficient connection (nexus) between the claimed invention and the success shown.
- A patentee may obtain a rebuttable presumption of nexus when it shows that the evidence of commercial success is tied to a specific product and that the product is essentially the invention disclosed and claimed (i.e., substantially coextensive with the claim).
- Once a prima facie case of nexus is shown (including by the presumption where applicable), the opposing party may rebut by showing the success is due to other causes such as unclaimed features, advertising, market power, or other external factors.
- Inequitable conduct requires clear and convincing evidence of both (a) materiality and (b) specific intent to mislead or deceive the USPTO; a finding cannot rest on materiality alone or on speculation about intent.

## Conclusion

The Federal Circuit reversed the district court’s rulings that the Barth patent claims were obvious and that the patent was unenforceable for inequitable conduct, holding that objective evidence like commercial success must be weighed when a proper nexus to the claimed invention is shown and that unenforceability demands clear and convincing proof of a deliberate intent to mislead the USPTO; the court therefore reversed the dependent no-infringement disposition and remanded.


Demaco Corp. v. F. Von Langsdorff Licensing Ltd., 851 F.2d 1387, 7 U.S.P.Q.2d 1222 (1988)