Federal Circuit Affirms District Court’s Invalidation of Patents Because Inventorship Could Not Be Corrected Without Giving All Inventors Notice and an Opportunity to Be Heard

In Fortress Iron, L.P. v. Digger Specialties, Inc, No. 24-2313, (Fed. Cir. Apr. 2, 2026), the Federal Circuit affirmed the United States District Court for the Northern District of Indiana’s invalidation of Fortress’ U.S. Patent Nos. 9,790,707 (“the ’707 patent”) and 10,883,290 (“the ’290 patent”) for incorrect inventorship.

The ’707 patent and ’290 patent name two Fortress employees as co-inventors. After it was sued for patent infringement, Digger Specialties uncovered, and Fortress acknowledged, that two additional employees from a third-party Fortress manufacturer were omitted as inventors on the asserted patents. Fortress added one of these employees as a coinventor but was unable to contact the other employee. The district court denied Fortress’s motion to correct the inventorship because, under 35 U.S.C. § 256, a patent can be corrected only “on notice and hearing of all parties concerned” and the absence of the second employee made that impossible. The district court thus held the patents invalid for omitting a co-inventor.

The Federal Circuit affirmed. It held the district court properly denied Fortress’s motion because an omitted inventor is a “concerned party,” and thus, must be afforded the opportunity to be heard under § 256(b). The Court emphasized the importance of § 256(b)’s procedural safeguards and determined that correction is barred if Fortress cannot satisfy the statutory requirements. Because the patents incorrectly omitted an inventor, and because Fortress cannot contact the omitted inventor, a prerequisite to § 256(b), the Court affirmed the district court's holding of invalidity. The Federal Circuit also affirmed the district court’s invalidation of incorrect inventorship under § 101 because the text of § 101 provides that “whoever invents . . . may obtain a patent thereof.” Reading § 100(f) in conjunction, the Federal Circuit held “‘[whoever]’ does not mean less than all” and that the repeal of pre-AIA § 102(f) did not eliminate invalidity due to an incorrect listing of inventors.