The United States District Court for the Northern District of Indiana denied Fortress’ motion and granted Digger’s motion, holding the ’707 and ’290 patents invalid based on the omission of the co-inventor.

Attribution of inventorship based on the inventors’ underlying advancements and discoveries is a bedrock of the patent system. Proper naming of inventors is required. 35 USC § 115(a) (“An application for patent … shall include, or be amended to include, the name of the inventor for any invention claimed in the application.”) Patents that do not name all the contributing inventors can be held invalid and unenforceable. While there are mechanisms for the correction of inventorship, the holding of Fortress Iron, LP v. Digger Specialties, Inc., No. 2024-2313, 2026 WL 899158 (Fed. Cir. Apr. 2, 2026), a case of first impression, presents an example of the consequences of omitting a co-inventor in view of the unusual circumstances of the omitted co-inventor being unreachable and unable to be located to make the correction.

Background

Fortress owns U.S. Patents 9,790,707 (the ’707 patent) and 10,883,290 (the ’290 patent) for vertical cable railing panels. Fortress worked with a Chinese entity, Quan Zhou Yoddex Building Material Co. Ltd. (YD), on the invention that would ultimately issue as the ’707 and ’290 patents. YD assisted in producing a prototype and two YD employees provided suggestions and input to resolve issues related to cable tensioning in the prototype. The suggestions were implemented into the final design. Fortress subsequently filed the patent applications that led to the issuance of the ’707 and ’290 patents.

The ’707 and ’290 patents each named the Fortress employees involved in the conception of the vertical cable railing panels as co-inventors but did not name any of the YD employees whose suggestions were implemented into the final design. One of the YD employees ended his term of employment at YD in 2016 and did not provide his contact information to either YD or Fortress (hereinafter “omitted inventor”).

Fortress sued Digger alleging infringement of the ’707 and ’290 patents. During the course of litigation, Digger learned of the inventive contributions of the two YD employees in the ’707 and ’290 patents. Fortress acknowledged the YD employees as co-inventors and sought to correct inventorship and add them as prescribed under 35 USC § 256(a). While one of the two YD employees was located and added as a co-inventor, the omitted inventor could not be located and was unable to be added.

The parties filed cross motions for summary judgment. Fortress sought partial summary judgment to correct inventorship of the ’707 and ’290 patents by adding the omitted inventor as a co-inventor pursuant to 35 USC § 256(b). Digger moved for summary judgment of invalidity asserting that the ’707 and ’290 patents were invalid for the omission of an inventor.

The United States District Court for the Northern District of Indiana denied Fortress’ motion and granted Digger’s motion, holding the ’707 and ’290 patents invalid based on the omission of the co-inventor. Fortress appealed the denial of partial summary judgment to correct inventorship under 35 USC § 256(b) and the grant of summary judgement to Digger holding the ’707 and ’290 patents invalid to the United States Court of Appeals for the Federal Circuit.

The Federal Circuit’s Decision

The court reaffirmed 35 USC § 256 as a “savings provision” where the district court must correct the patent at issue to prevent it from being held invalid if the statutory requirements for correction of the patent can be satisfied. However, the district court may only proceed to correct inventorship of the patent “on notice and hearing of all parties concerned.” 35 USC § 256(b).

Fortress argued that the district court erred in denying partial summary judgment to correct inventorship under 35 USC § 256(b), namely the determination that the omitted inventor was a “party concerned” under Section 256(b) such that he should have had the opportunity to be heard prior to correction of inventorship. The court disagreed and relied on the holding of Chou v. University of Chicago, 254 F.3d 1347 (Fed. Cir. 2001), which clarified the right of an inventor to be heard pursuant to Section 256(b) despite having no ownership interest in the patent, to determine that the omitted inventor was a “party concerned” under Section 256(b) and should be given notice and the opportunity to be heard as to the correction of inventorship. Although Fortress asserted that the omitted inventor could not be reached or located, the court emphasized that the provisions of Section 256(b) represent “a prerequisite to relief, not a mere formality.” Fortress Iron, 2026 WL 899158, at *3. The omitted inventor thus needs to be afforded the opportunity to be noticed and heard, and Fortress’ failure to satisfy this requirement of Section 256(b) renders it unable to correct inventorship of the patent via this statutory provision.

Fortress raised several counterarguments, advancing that: (i) a “party concerned” should be construed under the statute as a party having economic interest in the patent who would be adversely impacted by the addition of the party as a co-inventor to the patent; (ii) the omitted inventor would not have constitutional standing himself to seek correction of inventorship under Section 256(b) such that he is not a “party concerned”; and (iii) the district court erred in its restrictive application of Section 256(b) despite it being a savings provision.

The court dismissed these counterarguments. It is not known to any party what the full economic effect would be via the addition of the omitted inventor as a co-inventor, and interpretation of a “party concerned” to mean a party having an economic interest in the patent that would be adversely impacted is tantamount to rewriting the statute. Regarding constitutional standing, the court distinguished between constitutional standing and a “party concerned” under Section 256(b), each of which relates to different issues having different requirements, and dismissed Fortress’ attempt to conflate the two concepts, as one may be a “party concerned” pursuant to Section 256(b) but would need to separately demonstrate constitutional standing to invoke the correction of inventorship. See id. at *4 (citing Chou, 254 F.3d at 1357). With respect to the district court’s application of Section 256(b), the Federal Circuit reiterated that Fortress had failed to satisfy the statutory prerequisites for the omitted inventor to be noticed and heard, thereby rendering any such savings provision inapplicable.

Regarding the district court’s summary judgment holding the ’707 and ’290 patents invalid, Fortress argued on appeal that only one true inventor needs to be named on the patents based on the language of 35 USC § 101 indicating that “[w]hoever invents … may obtain a patent thereof” and that there is no need for joinder of all inventors for a patent to be valid in view of the repeal of pre-America Invents Act (AIA) 35 USC § 102(f). 35 USC § 101. The court similarly disagreed with Fortress.

First, with respect to Fortress’ assertion that only one true inventor needs to be named to render a patent valid, the court noted that Fortress’ position would introduce surplusage to the statutory text and render Section 256(b), directed to the correction of “the error of omitting inventors,” meaningless because there would be no need for the statute if just one true or correct inventor was named. 35 USC § 256(b) (emphasis added). The term “inventor” is also defined within the patent statute as “the individual or, if a joint invention, the individuals collectively who invented or discovered the subject matter of the invention” such that inventions having multiple inventors must name all the inventors. 35 USC § 100(f). Thus, use of the term “inventor” contemplates all individuals involved in the conception of the underlying invention.

Turning to Fortress’ arguments that the repeal of pre-AIA 35 USC § 102(f) no longer requires joinder of all inventors for a patent to be valid, the court clarified that pre-AIA 35 USC § 102(f) merely prevented an individual from obtaining a patent on an invention that they did not invent. Pre-AIA 35 USC § 102(f) thus had nothing to do with the omission of true inventors of a patent such that its repeal with the enactment of the AIA did not abrogate the finding of a patent invalid due to an erroneous listing of inventors.

The Federal Circuit ultimately affirmed the district court’s denial of partial summary judgment to correct inventorship of the ’707 and ’290 patents and affirmed the grant of summary judgment of invalidity of the patents due to incorrect inventorship because Fortress was unable to make a correction pursuant to Section 256.

Conclusion and Practice Points

Fortress Iron, LP v. Digger Specialties, Inc. represents an extreme and unusual situation in which an invalid patent for incorrect inventorship remains invalid because an omitted inventor cannot be reached or located, meaning they could not be noticed and heard pursuant to Section 256(b). As discussed, Section 256 is a savings provision that serves as a backstop to prevent patents from being found invalid for incorrect inventorship. Thus, there are numerous safeguards that should be put into place that would have averted having to consider correction of inventorship via this savings provision in the first place.

The identities of all inventors should be ascertained as early as possible during the preparation of a patent application. It may also be helpful for practitioners to explain and distinguish between who is an inventor under U.S. patent law versus attribution as a co-author on a manuscript to be submitted to a peer-reviewed scientific journal in the initial stages of representation so that inventive contributions can be readily ascertained. While seemingly tedious and time consuming, a thorough review of the application claim by claim to attribute conception of each claim to a particular individual, who will be named as a co-inventor, would also be helpful. Such safeguards would have prevented the situation in Fortress Iron as the contributions of the omitted inventor would have been recognized at the onset.

However, the scope of a patent application’s claims often changes from the original based on amendments made in response to an examiner’s determination of patentability such that certain individuals may need to be added as inventors or others removed based on the evolving scope of the claims in prosecution. Applicants or other stakeholders of interest should implement means for retaining the contact information of former employees who have made inventive contributions to one or more patent applications to facilitate making any necessary changes to inventorship.

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