In Dow Chemical Co. v. NOVA Chemicals Corp. (Canada), Nos. 14-1431, -1462 (Fed. Cir. Aug. 28, 2015), the Federal Circuit held that NOVA could relitigate during an appeal regarding supplemental damages whether the claims of U.S. Patent Nos. 5,847,053 and 6,111,023 are indefinite, an issue decided in a prior Federal Circuit appeal in 2012, because of a subsequent change in the law of indefiniteness.  The Court explained that, although the doctrines of law of the case and issue preclusion generally prohibit a party from relitigating a previously decided issue, they did not prevent NOVA from relitigating indefiniteness because supplemental damages requires a showing of infringement and “necessarily implicates patent validity.”  The Federal Circuit’s prior determination that the claims were not indefinite relied on case law abrogated by the Supreme Court’s Nautilus decision, which thus provided an exception to the applicability of law of the case and issue preclusion. 

Applying the new Nautilus standard, the Court held that the claims of the ’053 and ’023 patents are indefinite.  Each claim requires “a slope of strain hardening coefficient greater than or equal to 1.3,” which the Court noted could vary depending on which of four measurement methods was used to measure the slope.  Since a key figure illustrating how to measure slope was left out of the patent, the Court found that the specification provided no guidance as to which method should be applied.  Therefore, the Court held that the patent record did not convey to one of ordinary skill with reasonable certainty the scope of the invention, which rendered the claims indefinite.