Fortress Iron v. Digger Specialties — Federal Circuit Holds Patent Invalid When Omitted Co-Inventor Cannot Be Located for Correction

Background

Fortress Iron, LP designs and sells outdoor railing and fencing products. In 2013, its owner Matthew Sherstad conceived an idea for a vertical cable railing panel that could be sold pre-assembled, making installation easier. Fortress employee Kevin Burt sketched initial designs, and the team worked with two Chinese manufacturing partners — Hua-Ping Huang and Alfonso Lin of quality-control firm Yoddex — to resolve a prototype problem with cables rotating during tensioning. Huang and Lin’s suggestions fixed the issue and were incorporated into the final design. When Fortress filed patent applications, however, it named only Sherstad and Burt as inventors. U.S. Patent Nos. 9,790,707 and 10,883,290 issued without Huang or Lin on them.

In January 2021, Fortress sued Digger Specialties, Inc. (DSI) for patent infringement. During discovery, DSI uncovered evidence that Lin and Huang had contributed to the invention, and Fortress acknowledged they were co-inventors. Fortress located Lin and successfully added him to the patents using the standard inventorship correction procedure in 35 U.S.C. § 256(a), which requires consent and cooperation from all existing named inventors. Huang, however, had left the Chinese firm in 2016 and did not provide contact information to anyone — he was effectively unreachable.

Fortress then sought to add Huang under § 256(b), a separate provision that allows a court to order inventorship correction when proper proceedings have been had to notify all necessary parties. DSI moved for summary judgment of invalidity. The district court (N.D. Indiana) denied Fortress’s motion to correct and granted DSI’s invalidity motion. Fortress appealed.

The Court’s Holding

The Federal Circuit affirmed in a precedential opinion by Judge Lourie, holding that a patent which incorrectly lists its inventors and cannot be corrected under § 256 is invalid.

Section 256(b) requires notice and an opportunity to be heard — even for a missing inventor. Fortress argued it could correct inventorship under § 256(b) even though it could not locate Huang, contending that the “court” under § 256(b) could deem notice satisfied in a constructive sense. The Federal Circuit disagreed. Section 256(b) speaks of proceedings to “notify” parties and provide an opportunity to be “heard” — passive or constructive notice does not satisfy this requirement. Because Fortress could not actually give Huang notice of the correction proceeding, § 256(b)’s prerequisites could not be met, and the court was right to deny the motion.

Uncorrectable inventorship errors invalidate the patent. Section 256(b) contains an implicit invalidity rule: it states that errors of omitting inventors “shall not invalidate the patent . . . if it can be corrected.” The necessary implication is that omitting an inventor does invalidate the patent when the error cannot be corrected. Fortress argued that as long as at least one true inventor is named, a patent remains valid — but the Federal Circuit rejected this, holding it would render the § 256 savings provision meaningless. If omission of an inventor caused no invalidity risk, no “savings” would ever be needed.

The AIA repeal of § 102(f) did not change this. Fortress also argued that Congress’s repeal of pre-AIA § 102(f) (which had stated no patent may issue to someone who “did not himself invent” the subject matter) eliminated the invalidity consequence of incorrect inventorship. The Federal Circuit disagreed: § 102(f) merely confirmed that non-inventors cannot apply for patents; it was not the statutory basis for invalidity due to omitted inventors. Courts have long held that nonjoinder of a true inventor invalidates a patent, and that rule predates and survives the AIA.

Key Takeaways

• Any person who makes a genuine contribution to at least one patent claim is a co-inventor and must be named — omitting even one true inventor can sink the entire patent if the error cannot be fixed later.
• The § 256(b) escape hatch for correcting inventorship requires that every relevant party receive actual notice and an opportunity to participate — if a co-inventor is unreachable, this safety valve may not be available.
• The risk is asymmetric: a supplier, contractor, or vendor employee who suggests a design feature that solves a key technical problem can become a co-inventor, even if they are not employed by the patent applicant and even if the applicant never considered them an inventor.
• Companies should conduct thorough inventorship analysis before filing — and document the contributions of every person who worked on the invention, including outside collaborators and manufacturing partners — while those people are still reachable.

Why It Matters

This ruling is a cautionary tale for manufacturers who work with overseas suppliers and contract manufacturers during product development. When vendor employees or other third-party contributors weigh in on design decisions — especially those that solve key technical problems — they may legally become co-inventors. If their contributions go unrecognized at the time of filing and they cannot later be located to participate in a § 256(b) proceeding, the resulting patent may be permanently unenforceable.

The decision reinforces the importance of robust inventorship protocols early in the patent process: document who contributed what, collect contact information, and get any necessary inventor oaths at the outset. Attempting to correct inventorship during litigation — when a co-inventor may have long since moved on — is a high-risk strategy that can wipe out the entire patent portfolio. The Federal Circuit’s holding that § 256(b) requires actual notice (not constructive notice) to the missing inventor raises the bar further for patent owners who discover a problem late.

Surfaced via Law360 IP commentary on incorrect inventorship.