Patent Invalidity Due To Incorrect Inventorship

Inventorship is an often overlooked detail in patent law that is a statutory condition tied to validity, ownership, standing, and enforceability. The Federal Circuit’s recent decision in Fortress Iron, LP v. Digger Specialties, Inc., 171 F.4th 1310 (Fed. Cir. 2026), makes that point sharply: where a patent omits a true inventor and the error cannot be corrected under 35 U.S.C. § 256, the patent is invalid.

In Fortress, the patents initially named only Fortress’s owner and an employee as inventors. Fortress later acknowledged that two vendor-side employees, Alfonso Lin and Hua-Ping Huang, were coinventors. Although Fortress added Lin through the PTO process, it could not locate Huang and sought court-ordered correction under Section 256(b). The Federal Circuit affirmed summary judgment of invalidity because Huang was an omitted coinventor and Fortress could not satisfy Section 256(b)’s notice-and-hearing requirement.

The decision is important because the omitted inventor was not contesting inventorship; he simply could not be found. The court nevertheless held, as a matter of first impression, that an agreed-upon omitted coinventor is a “party concerned” under Section 256(b) and must receive notice and an opportunity to be heard before correction. As the court put it, “[i]nventors occupy the central role in the patent process” and “their explicit references in the statutory framework cannot be taken lightly.” Fortress Iron, 171 F.4th at 1314–15. Inventorship carries legal, financial, and ownership consequences, including the default rule that each joint owner may exploit the patent without accounting to the others. Id. at 1315. Because Fortress could not contact Huang, Section 256(b)’s notice requirement was “a prerequisite to relief, not a mere formality.” Id.

Inventorship Framework and Analysis
The broader framework begins with the principle that a patent must name the true inventors of the claimed subject matter. In Pannu v. Iolab Corp., 155 F.3d 1344 (Fed. Cir. 1998), the Federal Circuit explained that “if nonjoinder of an actual inventor is proved by clear and convincing evidence, a patent is rendered invalid,” but Section 256 operates as a “savings provision” if correction is available. Pannu, 155 F.3d at 1349–50. Thus, the court first asks whether clear and convincing evidence shows that an omitted person was a coinventor; if so, the patentee must obtain correction or face invalidity for failure to name the proper inventive entity.

An inventorship analysis under Section 256 is claim-centered. The court does not ask in the abstract who helped with the project; it asks who contributed to conception of the claimed invention. In Trovan Ltd. v. Sokymat SA, 299 F.3d 1292 (Fed. Cir. 2002), the Federal Circuit stated that inventorship is determined claim-by-claim, beginning with claim construction and then comparing the alleged contributions to the properly construed claims. Trovan, 299 F.3d at 1302–03. A joint inventor need not contribute to every claim or contribute equally, but each must make an inventive contribution, not merely exercise ordinary skill or explain the state of the art.

That inquiry also requires evidence. Because issued patents are presumed to name the correct inventors, misjoinder or nonjoinder must be proven by clear and convincing evidence. Trovan, 299 F.3d at 1301–03. The alleged inventor’s testimony generally must be corroborated under a “rule of reason,” with contemporaneous documents or physical records often carrying particular weight. Id. at 1302–03.

The remedy question is therefore binary but sequential. Section 256 allows correction of misjoinder and nonjoinder, including complete substitution of inventors where appropriate, and post-AIA § 256 no longer requires that nonjoinder have occurred “without deceptive intention.” Id. at 1301. But Fortress confirms that the error avoids invalidity only “if it can be corrected.” Fortress Iron, 171 F.4th at 1316. If the patentee cannot satisfy the statute’s conditions—there, notice and hearing for all “parties concerned”—the savings provision does not apply. The Federal Circuit therefore held that “a patent which incorrectly lists its inventor(s) and cannot be corrected according to law is invalid.” Id. at 1317.

Article III Standing
A plaintiff seeking correction must also establish Article III standing. Section 256 may create the cause of action, but federal jurisdiction still requires injury in fact, causation, and redressability. Larson v. Correct Craft, Inc., 569 F.3d 1319, 1326–27 (Fed. Cir. 2009). In Larson, the purported inventor lacked standing because he had already assigned away his patent rights, had no non-contingent financial interest in the patents, and alleged no reputational injury (leaving open the question “whether a purely reputational interest is sufficient to confer standing for a § 256 claim.”). Id. at 1327–28. Later, Shukh v. Seagate Technology, LLC held that a concrete and particularized reputational injury can support Article III standing in a Section 256 action. Shukh v. Seagate Technology, LLC, 803 F.3d 659, 663–67 (Fed. Cir. 2015). The court emphasized that “being considered an inventor of important subject matter is a mark of success in one’s field,” and found a triable issue because the omission could have harmed Shukh’s reputation as an inventor and affected his employment prospects. Id. at 663–67. Fortress adds an important distinction: constitutional standing and “party concerned” status under Section 256(b) are not the same thing, so an omitted coinventor may be entitled to notice and a hearing even if that person’s own standing to bring an affirmative Section 256 claim would be contested. Fortress, 171 F.4th at 1315.

Defensive Arguments
For a defendant, laches can be a defense to a Section 256 claim. In Hor v. Chu, 699 F.3d 1331 (Fed. Cir. 2012), the Federal Circuit explained that laches requires unreasonable, inexcusable delay plus material prejudice attributable to that delay. Hor, 699 F.3d at 1334. For Section 256 claims, a six-year delay after accrual creates a rebuttable presumption of laches. Id. The claim does not accrue before issuance, however, because Section 256 concerns issued patents; the period begins when the omitted inventor knew or should have known of the patent’s issuance. Id. at 1334–37.

Employment and consulting agreements add a layer of analysis to standing because inventorship and ownership are distinct. An inventor may be correctly named even after assigning away economic rights, and a company may own patent rights without changing who conceived the claimed invention. In DDB Technologies, L.L.C. v. MLB Advanced Media, L.P., 517 F.3d 1284 (Fed. Cir. 2008), the employee agreement stated that the employee “agrees to and does hereby grant and assign” rights in covered future inventions. The Federal Circuit held that this was an express assignment of future invention rights, so title transferred automatically when the invention came into being. DDB, 517 F.3d at 1290. The wording matters. Under DDB, language that expressly grants rights in future inventions—such as “does hereby grant and assign”—can create an automatic assignment, while a mere promise to assign may create equitable rights but not immediate legal title. With this in mind, a plaintiff who previously signed an automatic assignment would not have standing to later pursue a Section 256 claim.

Conclusionary Takeaways
As for the key takeaways, companies should use present-tense assignment language for employees and contractors who may invent—“hereby assigns” or equivalent wording—rather than relying only on a promise to assign later. They should also include invention-disclosure duties, prosecution and correction cooperation obligations, and current-contact-information requirements for inventors and key technical contributors. The problem in Fortress was that, by the time the issue mattered, one agreed-upon coinventor could not be located, and notice to him was a statutory prerequisite to correction.

Companies should also treat collaboration records as evidence, not administrative clutter. Meeting notes, prototype access logs, invention disclosures, NDA files, technical presentations, and contemporaneous emails can become decisive in showing who conceived what and when. The safest practice is to evaluate inventorship before filing, revisit it before issuance and continuation filings, and promptly correct errors while all parties concerned can still be reached.

Fortress is ultimately a cautionary case about timing and precision. Section 256 remains powerful, but it does not guarantee that every inventorship error can be fixed after the fact. When the true inventive entity cannot be established, or statutory correction requirements cannot be satisfied, incorrect inventorship can still be fatal. For patent owners, the best protection is front-end discipline: claim-by-claim inventorship review, robust assignment language, reliable inventor contact information, and documented collaborative contributions before any dispute reaches court.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.