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Chill out: Numerical claim terms properly limited by industry standards

by | May 21, 2026 |

The US Court of Appeals for the Federal Circuit affirmed a noninfringement finding, concluding that a claim limitation reciting a pH range having only a lower limit referred to pH measured at standard temperature in the art. The Court also found that prosecution history estoppel and the disclosure-dedication rule foreclosed reliance on the doctrine of equivalents to capture a pH below the express lower limit. Actelion Pharms. Ltd. v. Mylan Pharms. Inc., Case No. 24-1641 (Fed. Cir. May 13, 2026) (Reyna, Taranto, Stoll, JJ.)

Actelion owns patents covering lyophilized epoprostenol formulations used to treat cardiovascular disease. Epoprostenol is unstable in water because acidic conditions catalyze its degradation. The patents sought to improve stability by manufacturing highly basic bulk solutions, thereby producing freeze-dried formulations that remained stable after reconstitution in typical intravenous fluid. The asserted claims recite bulk solutions having a pH “of 13 or higher” or “greater than 13.”

Mylan sought approval to market a generic version of Actelion’s Veletri® product and was sued under 35 U.S.C. § 271(e)(2). The district court construed “a pH of 13 or higher” to mean “a pH of 12.98 or higher.”

It was undisputed that Mylan’s bulk solution measured below a pH of 12.98 at standard temperature (25±2°C). Actelion nevertheless contended that infringement existed because the solution exceeded pH 13 at lower temperatures during refrigerated manufacturing.

The district court disagreed, finding that the claim term “a pH of 13 or higher” referred to a pH measured at a temperature standard in the field, and that therefore Mylan did not literally infringe. The district court further ruled that Actelion was barred from asserting and had not proved infringement under the doctrine of equivalents. Actelion appealed.

The Federal Circuit agreed with the district court that a person of ordinary skill would interpret the claimed pH values as measurements taken at standard temperature, absent an express indication otherwise. Although the claims did not specify measurement conditions, the specification consistently treated pH values as standard-temperature measurements. The Court emphasized that the specification compared results across pH levels without suggesting temperature-dependent variation and described an “alkaline environment” as “pH > 7,” a statement accurate only at standard temperature.

The Federal Circuit found that extrinsic evidence reinforced that understanding. The United States Pharmacopeia and expert testimony established that, in pharmaceutical formulations, pH is ordinarily measured at 25±2°C unless otherwise specified. The Court found no clear error in the district court’s factual findings on industry practice.

Because Mylan’s product failed to meet the pH limitation under that standard, the Federal Circuit affirmed the finding of no literal infringement.

The Federal Circuit also rejected Actelion’s doctrine of equivalents theory. During prosecution, Actelion amended the claims from “greater than 12” to “a pH of 13 or higher” after the examiner recognized unexpected results at pH 13 but not at pH 12. The Court found that this narrowing amendment gave rise to prosecution history estoppel, barring Actelion from recapturing lower pH values through equivalence.

Separately, the Federal Circuit applied the disclosure-dedication rule. The patents [...]

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Appellate deference: Reinforcing limits on reweighing evidence

by | May 21, 2026 |

Clarifying the proper scope of appellate review, the US Court of Appeals for the Federal Circuit affirmed an International Trade Commission final determination in full. The Court upheld the scope of the exclusion of only certain accused products and permitted importation of redesigned versions, concluding that the Commission correctly viewed the evidence and claim terms. Bissell, Inc. v. ITC, Case No. 24-1509 (Fed. Cir. May 11, 2026) (Moore, Taranto, Stoll, JJ.)

Bissell initiated a Section 337 investigation alleging that Tineco Intelligent imported wet/dry surface-cleaning devices that infringed Bissell’s patents. Following an evidentiary hearing, the administrative law judge (ALJ) found infringement of Tineco’s original products and recommended exclusion but concluded that Tineco’s redesigned products did not infringe and therefore fell outside the scope of relief.

The Commission affirmed the ALJ’s determination, which resulted in a limited exclusion order directed to the infringing products only. Both parties appealed.

Bissell challenged the finding that Tineco’s redesigned products did not literally infringe a limitation requiring that “the battery charging circuit is disabled” during the “self-cleaning mode . . . and remains disabled during the . . . cleanout cycle.” Tineco modified its products so that some battery charging did occur during a “self-cleaning mode,” but battery charging was disabled for most of the cleaning cycle. Before the ALJ, Bissell’s expert opined that infringement of this claim essentially only required a period in which self-cleaning occurred and while the battery charger was disabled. The ALJ rejected Bissell’s theory, determining that the claim required the battery charger to “remain[] disabled during the . . . cleanout cycle.”

According to Bissell, the ALJ’s conclusion amounted to improper claim construction. The Federal Circuit disagreed, finding that the ALJ had merely applied the plain and ordinary meaning of the claim term. As Bissell had not disputed that the ALJ’s findings were supported by substantial evidence, the Federal Circuit affirmed these findings.

Tineco cross-appealed the ALJ’s determination that Bissell’s domestic industry products satisfied the disabled battery limitation. According to Tineco, the evidence was inadequate to support the ALJ’s determination because the source code that Bissell’s expert relied on was never produced during the Commission trial.

The Federal Circuit found that Bissell’s expert testimony was sufficient under Federal Rule of Evidence 703, which permits experts to rely on facts or data they have been made aware of or personally observed, even if those materials are not themselves admissible, as long as they are of a type reasonably relied upon in the field. The Court emphasized that neither party disputed that experts in this context routinely rely on source code to assess infringement. The Court further concluded that substantial evidence supported the ALJ’s determination, highlighting that:

  • The source code had been produced during discovery.
  • The expert’s opinions were not conclusory.
  • Tineco did not meaningfully test the testimony through cross-examination or offer competing expert analysis.
  • The ALJ’s findings were independently corroborated by a Bissell internal document admitted at trial.

Practice note: Where the Commission uses the “face of the claim to [...]

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Words of approximation require more precision after narrowing amendments

by | May 14, 2026 |

The US Court of Appeals for the Federal Circuit affirmed a judgment of indefiniteness, concluding that the use of the term “about” to define a critical pH limitation failed to inform skilled artisans of claim scope with reasonable certainty under 35 U.S.C. § 112. Enviro Tech Chemical Services, Inc. v. Safe Foods Corp., Case No. 24-2106 (Fed. Cir. May 4, 2026) (Lourie, Prost, Burroughs, JJ.)

Enviro Tech owns a patent that claims a method for treating poultry during processing to increase the weight of the poultry by using peracetic acid. Each claim in the patent requires the step of altering the pH of the peracetic-acid-containing water to “a pH of about 7.6 to about 10” by adding an alkaline source.

During claim construction, the district court concluded that the term “about” was indefinite, finding that the intrinsic evidence did not inform a skilled artisan as to the scope of the term “about” with reasonable certainty. Enviro Tech appealed.

The Federal Circuit has long held that words such as “about” and “approximately” may be appropriately used to avoid a strict numerical boundary to the specified parameter. However, when a word of approximation is used, the parameter’s range must be reasonably certain based on the “technological facts of the particular case” and considering the claims, specification, prosecution history, and extrinsic evidence.

Starting with the claims, the Federal Circuit found that they failed to provide meaningful guidance on how far below a pH of 7.6 or above a pH of 10 the peracetic-acid-containing water could fall and still satisfy the limitation. Although the parties agreed that “about” ordinarily means “approximately,” the Court concluded that substituting one term for the other does not clarify the permissible deviation from the claimed range or otherwise inform a skilled artisan of the scope of the claims.

The Federal Circuit next turned to the specification, finding that it also failed to define the scope of “about” with reasonable certainty because it provided inconsistent guidance on acceptable pH deviations. Although the specification disclosed experiments where Enviro Tech only proceeded when the measured pH was within 0.3 of the target, the specification also described instances where Enviro Tech continued experiments despite larger deviations, including a large scale poultry processing test with pH variances of up to 0.5. Given these unexplained exceptions (particularly in a commercially significant real world setting) the Court found that the 0.3 threshold could not be treated as a reliable boundary for “about.” Thus, the Court found that the specification’s conflicting examples left skilled artisans without clear notice of the claimed scope.

Turning to the prosecution history, the Federal Circuit found that Enviro Tech treated the term “about” inconsistently. For instance, in one office action response, Enviro Tech argued that “a peracetic acid solution at the lower end of the claimed range, pH 7.6,” would not have been obvious over the prior art, notably omitting the word “about.” Yet on the very next page, Enviro Tech asserted that “a step of adjusting the pH to the range [...]

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Lost in the constellation: Result-oriented claims miss the mark under § 101

by | May 7, 2026 |

Addressing issues related to patent eligibility, infringement, and damages, the US Court of Appeals for the Federal Circuit vacated in part, affirmed in part, and remanded, finding that certain result-oriented claims were directed to an abstract idea, lacked an inventive concept, and were therefore not patent eligible. Constellation Designs, LLC v. LG Electronics Inc., et al., Case No. 24-1822 (Fed. Cir. Apr. 28, 2026) (Lourie, Stoll, Oetken, JJ.)

Constellation sued LG for infringing its patents directed to communication systems employing non-uniform constellations, which are signal configurations designed to improve data transmission capacity compared to conventional uniform constellations. The accused products were LG televisions compliant with the ATSC 3.0 broadcast standard.

Constellation successfully moved for summary judgment in its favor on patent eligibility under 35 U.S.C. § 101. At trial, Constellation asserted nine claims across four patents, which the parties grouped into two categories: “optimization claims,” which recited constellations optimized for capacity, and “constellation claims,” which recited specific non-uniform constellation configurations. A jury found willful infringement and awarded damages. The district court denied LG’s motions for judgment as a matter of law (JMOL) of noninfringement and no damages. LG appealed.

On the patent eligibility issue, the Federal Circuit applied the two-step Alice framework and vacated the district court’s ruling as to the optimization claims. At step one, the Court found those claims directed to the abstract idea of optimizing a constellation for parallel decoding capacity. The Court emphasized that the claims were written in a result-oriented manner, reciting a constellation “optimized” for capacity without specifying how that optimization was achieved. Although the claims did not cover every possible optimization technique, they were broad enough to encompass all ways of optimizing a constellation for parallel decoding capacity. The Court rejected Constellation’s reliance on technical details in the specification and reiterated that the § 101 inquiry focuses on the claim language, not unclaimed implementation details. At step two, the Court found no inventive concept, explaining that Constellation’s alleged innovation was the abstract idea itself and that arguments based on novelty or nonobviousness do not satisfy § 101.

In contrast, the Federal Circuit affirmed the district court’s eligibility determination for the constellation claims. The Court explained that representative claims recited specific, concrete configurations (such as unequally spaced constellation points, distinct labeling, and overlapping point locations) amounting to a particular technological solution to a defined problem. Because those claims were not directed to an abstract idea, the Court did not proceed to step two.

On infringement, the Federal Circuit affirmed the denial of JMOL. The Court clarified that a patentee may rely on industry standard compliance to prove some claim limitations while using product-specific evidence for others, as long as the standard is sufficiently specific and either mandatory or shown to be implemented in the accused products. Applying that framework, the Court found that substantial evidence supported the jury’s verdict.

As for damages, the Federal Circuit affirmed the denial of LG’s JMOL motion and its challenge to the admissibility of Constellation’s damages expert. The Court [...]

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Missed delivery: Institution decision statutorily unreviewable

by | May 7, 2026 | ,

Addressing the scope of appellate review under the America Invents Act, the US Court of Appeals for the Federal Circuit determined that challenges grounded in 35 U.S.C. § 312(a)(2)’s real-party-in-interest requirement are unreviewable where they are closely tied to the Patent Trial & Appeal Board’s institution decision. Fed. Express Corp. v. Qualcomm Inc., Case No. 24-1236 (Fed. Cir. Apr. 29, 2026) (Hughes, Cunningham, Stark, JJ.)

FedEx owns a patent related to sensor-based logistics systems that provide shipment information and allow customized access controls. After FedEx sued Roambee for infringement in district court, Qualcomm (although not a party to that litigation) filed inter partes review (IPR) petitions challenging the FedEx patent. Qualcomm identified the Roambee litigation as a related matter but did not list Roambee as a real party in interest.

FedEx opposed institution, arguing that Qualcomm’s failure to identify all real parties in interest violated § 312(a)(2), which requires that a petition identify all such parties before it may be considered. The Board instituted review and later denied FedEx’s motion to terminate, explaining that it would not decide the real-party-in-interest issue because doing so was unnecessary to resolve the proceeding absent a time-bar or estoppel concern. In its final written decision, the Board declined to revisit the issue and held the challenged claims unpatentable as obvious. FedEx appealed.

On appeal, the Federal Circuit declined to review FedEx’s real-party-in-interest challenges. Relying on Supreme Court precedent and its own case law, the Federal Circuit explained that § 312(a)(2) is a statutory prerequisite “closely tied” to institution because a petition may be considered only if it identifies all real parties in interest. Thus, challenges asserting that the Board failed to properly apply § 312(a)(2) necessarily attack the institution decision itself and fall within § 314(d)’s bar on appellate review.

The Federal Circuit rejected FedEx’s attempt to reframe its arguments as a challenge to the Board’s post-institution conduct, including the denial of FedEx’s motion to terminate. The Court explained that even when raised later in the proceeding, such arguments “boil down” to whether the Board should have instituted IPR in the first place. Because § 312(a)(2) operates as a prerequisite to institution, those challenges remain unreviewable.

Turning to the merits, the Federal Circuit vacated the Board’s obviousness determination as to several claims. The Board had found those claims obvious based on a combination of prior art because it believed FedEx had not contested that ground. Both parties agreed on appeal that this premise was incorrect: FedEx had in fact disputed the combination. Because the Board’s analysis rested on a mistaken understanding of the record and failed to address FedEx’s arguments or fully evaluate the prior art, the Court concluded that meaningful appellate review was not possible and vacated the Board’s obviousness determination.

The Federal Circuit declined FedEx’s request for outright reversal of the Board. The Court explained that reversal is appropriate only where the record supports a single outcome, but here unresolved factual issues remained, including whether the prior art satisfied the relevant claim [...]

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Patent disclosure erases trade secret protection

by | Apr 30, 2026 | ,

Addressing the boundary between patent disclosures and trade secret protection, the US Court of Appeals for the Federal Circuit reversed a jury’s findings of trade secret misappropriation, breach of contract, and improper inventorship, concluding that the asserted “trade secrets” were generally known and therefore not protectable under California law. The Court affirmed, however, a $1 million statutory damages award for trademark counterfeiting. International Medical Devices, Inc. v. Cornell, Case Nos. 25 1580; 1605 (Fed. Cir. Apr. 17, 2026) (Dyk, Reyna, Taranto, JJ.)

International Medical Devices, Menova International, and Dr. James Elist (collectively, the plaintiffs) manufacture and sell the Penuma® cosmetic penile implant. The plaintiffs sued Dr. Robert Cornell and associated individuals and entities after Cornell attended a Penuma® surgical training session under a nondisclosure agreement (NDA) and later helped develop a competing implant. The plaintiffs asserted claims for misappropriation of trade secrets, breach of the NDA, trademark counterfeiting based on unauthorized use of the Penuma® mark, and invalidity of two cosmetic implant patents for failure to name Elist as an inventor.

A jury found for the plaintiffs on all claims. After a bench trial on remedies, the district court awarded more than $17 million in trade secret and exemplary damages, entered a permanent injunction, and awarded $1 million in statutory damages for counterfeiting. Cornell appealed.

The Federal Circuit reversed the trade secret verdict in its entirety, concluding that none of the asserted trade secrets were protectable under California law. The Court concluded that the alleged technical trade secrets were disclosed in publicly available patents and thus were “generally known” as a matter of law.

In doing so, the Federal Circuit reaffirmed the long-standing principle that “that which is disclosed in a patent cannot be a trade secret.” Once information enters the public domain through patent disclosures, it cannot later be reclaimed as confidential business information through trade secret law.

The plaintiffs’ remaining alleged trade secret (a list of surgical instruments) fared no better. The Federal Circuit found that the list had been emailed to the defendants without any confidentiality designation or obligation, defeating any claim that reasonable measures were taken to maintain its secrecy.

Because the plaintiffs failed to identify any confidential information beyond the alleged trade secrets, the Federal Circuit also reversed the breach of contract verdict. The NDA expressly excluded information that was “generally available to the public,” and the Court found that an NDA cannot transform public domain information into protected confidential material.

The Federal Circuit reached a different conclusion on trademark counterfeiting, however, and affirmed the jury’s finding and the $1 million statutory damages award. The Court explained that the evidence showed that Cornell had advertised and offered Penuma® implants without authorization. Cornell argued that the Penuma® mark was registered only for goods, not services, and therefore could not support a counterfeiting claim tied to surgical procedures. The Court rejected that argument, concluding there was sufficient evidence that Cornell offered the Penuma® implant itself as a good, not merely a medical service.

Finally, the Federal Circuit [...]

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Public use, even without explicit public disclosure, is patent bar under pre-AIA § 102(b)

by | Apr 23, 2026 |

The US Court of Appeals for the Federal Circuit affirmed summary judgment of invalidity under the pre-America Invents Act (AIA) on sale bar, holding that a third party sale to the public of a product embodying a patented method and apparatus can trigger invalidity even where details of the invention were not expressly disclosed. Definitive Holdings v. Powerteq, Case No. 24-1761 (Fed. Cir. Apr. 14, 2026) (Moore, Dyk, Cunningham, JJ.)

Definitive Holdings sued Powerteq alleging infringement of a patent directed to methods and systems for reprogramming engine controllers. With a priority date of March 30, 2001, the patent was subject to pre-AIA law. Powerteq moved for summary judgment of invalidity under pre-AIA 35 U.S.C. § 102(b), arguing that a nonparty, Hypertech, had sold a product (the PP3) that embodied all limitations of the asserted claims more than one year before the patent’s priority date.

Rather than disputing the underlying facts, Definitive challenged the admissibility of the evidence on which Powerteq relied. Definitive argued that the deposition testimony of Hypertech’s Rule 30(b)(6) witness, the PP3 source code, and expert testimony relying on that source code were inadmissible. The district court rejected those arguments and granted summary judgment of invalidity, concluding that the third party sales triggered the on sale bar. Definitive appealed.

The Federal Circuit reviewed the summary judgment ruling de novo, applying Tenth Circuit law.

Definitive first argued that the district court improperly relied on testimony from Hypertech’s Rule 30(b)(6) witness, Hypertech CEO and owner Jay Ramsay. The Federal Circuit disagreed, finding that Ramsay’s testimony was based on his personal knowledge and thus was sufficient to authenticate Hypertech’s sales records and establish that Powerteq’s expert analyzed source code from the PP3 product.

The Court explained that a reasonable juror could conclude that Ramsay had personal knowledge of Hypertech’s recordkeeping practices and sales activities. Because those portions of the testimony were sufficient to support summary judgment, the Court declined to address whether other portions of the 30(b)(6) testimony were properly considered and how the Tenth Circuit generally treats Rule 30(b)(6) testimony at summary judgment.

Definitive next argued that the PP3 source code and related expert testimony constituted inadmissible hearsay. The Federal Circuit disagreed. The Court explained that while comments or annotations in source code could, in some circumstances, qualify as hearsay statements, the operative source code itself functions as a set of commands or instructions. As such, it is not offered for the truth of any assertion. The Court therefore found that the district court did not abuse its discretion in considering expert testimony describing the functioning of the source code when granting summary judgment.

Finally, Definitive contended that the on sale bar did not apply because Hypertech’s sales of the PP3 did not publicly disclose how to perform the patented method, even if the PP3 embodied all claim limitations and was sold more than one year before the priority date.

The Federal Circuit rejected Definitive’s argument, emphasizing that Hypertech’s sales directly conveyed to the public the ability to practice the [...]

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Article III standing: Claims of future injury must be sufficiently tied to the claim limitations at issue

by | Apr 16, 2026 |

The US Court of Appeals for the Federal Circuit dismissed an appeal of a post-grant review (PGR) for lack of Article III jurisdiction, finding that the appellant failed to meet its burden to prove it would likely suffer an injury in fact. ironSource Ltd. v. Digital Turbine, Inc., Case No. 2024-1831 (Fed. Cir. Apr. 7, 2026) (Moore, Lourie, Reyna J.J.)

Mobile advertising company Digital Turbine has a patent related to streamlined background processes for downloading and installing mobile applications. That patent is a continuation an earlier related patent which was invalidated during a prior PGR proceeding. Mobile advertising and app monetization platform ironSource once had a product on the market called Aura, which included “Click to Install” features. When faced with what it referred to as “veiled threats” of liability for infringement of the earlier patent, ironSource modified its Aura product – eventually removing it from the market – and petitioned the Patent Trial & Appeal Board for a PGR of the continuation patent’s claims 1 – 22.

During the PGR, the Board held that claims 1 – 22 were all unpatentable pursuant to its earlier decision in the earlier PGR but allowed Digital Turbine to amend the claims. In so doing, Digital Turbine included, among other changes, two narrowing limitations to the claims. The Board concluded that ironSource had not carried its burden of proving that the newly amended claims were unpatentable or ineligible for patent protection. ironSource appealed.

On appeal, the Federal Circuit explained that while Article III standing is not required before the Board, it is required to sustain an appeal of the Board’s decisions. The burden is on the appellant to prove it meets the requirements for standing under federal law at the time of filing. Federal law requires an appellant to prove it has “(1) suffered an injury in fact, (2) that is fairly traceable to the challenged conduct of the [appellee], and (3) that is likely to be redressed by a favorable judicial decision.” Spokeo. Specific to patent cases, the appellant must show concrete evidence of its intended future actions that pose a substantial risk of infringement or an assertion of infringement.

To meet this obligation, ironSource submitted a declaration by one of its senior directors. The declarant discussed past changes and concessions to the Aura product that ironSource had made in light of Digital Turbine’s patent rights. It also stated that ironSource intended to reintroduce the Aura product to the market. Nevertheless, the Federal Circuit held that ironSource failed to meet its burden of tying that potential product’s features to the patent’s amended claims. Instead, ironSource focused on the claims of the original, alleging that they were “substantially identical” to the continuation patent’s claims, i.e., the claims Digital Turbine had previously “threatened” against the company. The Court emphasized, however, that ironSource failed to account for the narrowing limitations in the amended claims and thus failed to prove a likely injury in fact from infringement of the substituted claims.

Finally, the Federal Circuit distinguished [...]

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“X” marks the spot: A single DuPont factor may be dispositive

by | Apr 16, 2026 |

The US Court of Appeals for the Federal Circuit affirmed dismissal of a trademark opposition, concluding that a single DuPont factor may be sufficient on its own to support a finding of no likelihood of confusion. Fuente Mktg. Ltd. v. Vaporous Techs., LLC, Case No. 24-1460 (Fed. Cir. April 8, 2026) (Prost, Taranto, Hughes, JJ.)

Fuente Marketing and Vaporous Technologies both sell smoking related products. Fuente owns two standard character trademark registrations for the letter “X,” used in connection with cigars and related accessories. Vaporous sought to register a highly stylized design mark for use with its vaping products. The parties stipulated that Vaporous’ mark consisted of “an abstract stick figure consisting of two diagonal intersecting lines in the shape of a wide stylized letter ‘X’ with a shaded circle above.”

Fuente opposed the application at the Trademark Trial and Appeal Board (TTAB), arguing that Vaporous’ mark was likely to cause confusion with Fuente’s “X” marks. Applying the DuPont factors, the Trademark Trial & Appeal Board dismissed the opposition, concluding that there was no likelihood of confusion. Fuente appealed.

The Federal Circuit reviewed the Board’s factual findings for substantial evidence and its ultimate likelihood of confusion determination de novo. Fuente challenged the Board’s analysis of two DuPont factors and argued that the Board improperly weighed the factors as a whole.

The Federal Circuit focused on the first DuPont factor, which evaluates the similarity or dissimilarity of the marks in their entireties as to appearance, sound, connotation, and commercial impression. The court found that substantial evidence supported the Board’s finding that this factor weighed heavily against a likelihood of confusion. The Federal Circuit agreed that consumers were more likely to perceive Vaporous’ mark as a stylized stick figure rather than the letter “X.” Unlike Fuente’s standard character mark, Vaporous’ design mark did not sound like the letter “X” as it had no pronunciation, and it incorporated prominent visual features – including a shaded circle comprising roughly one fifth of the mark – that were “not a minor or unnoticeable feature.”

Although the Board found that the remaining DuPont factors were neutral or favored Fuente, the Federal Circuit explained that it could “discern the Board’s path to dismissal” and affirmed the conclusion that in a case like this one DuPont factor was sufficient to establish dissimilarity between the marks. The Court emphasized that a likelihood of confusion analysis is a balancing test, and no minimum number of factors must favor one party.

Practice note: This decision reinforces that a single DuPont factor, particularly the dissimilarity of the marks, may be dispositive of likelihood of confusion. Parties should not assume that favorable findings on other factors can overcome a clear lack of similarity in appearance, sound, connotation, or commercial impression.



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Where’s Waldo? Inventorship error fatal when omitted coinventor cannot be found

by | Apr 16, 2026 |

Addressing the limits of correcting inventorship, the US Court of Appeals for the Federal Circuit affirmed an invalidity determination where an omitted coinventor could not be added because statutory notice requirements could not be satisfied. Fortress Iron, LP v. Digger Specialties, Inc., Case No. 24-2313 (Fed. Cir. Apr. 2, 2026) (Lourie, Hughes, Kleeh, JJ.)

Building products manufacturer Fortress Iron sued competitor Digger Specialties for infringement of two patents directed to pre assembled vertical cable railing panels. The inventions resulted from collaboration among Fortress’ owner and an employee, as well as two employees of its quality control liaison, Hua Ping Huang and Alfonso Lin, who proposed design changes to address cable tensioning issues. The issued patents, however, named only Fortress personnel and omitted Lin and Huang as coinventors.

During the litigation, Fortress acknowledged that Lin and Huang were coinventors. Fortress successfully added Lin under 35 U.S.C. § 256(a) but was unable to locate Huang, who had left the liaison company years earlier without providing contact information. The parties filed cross motions for summary judgment, with Fortress seeking correction of inventorship and Digger seeking invalidity. The district court denied Fortress’ motion and held the patents invalid for incorrect inventorship. Fortress appealed.

Fortress argued that Huang was not a “party concerned” under § 256(b) and therefore was not entitled to notice and a hearing. The Federal Circuit rejected that argument, explaining that an omitted inventor qualifies as a “party concerned” regardless of whether the inventor has a demonstrated economic interest in the patent. The Court explained that inventorship carries legal, financial, and ownership consequences that an inventor has a right to contest, and § 256(b)’s notice and hearing requirements cannot be bypassed. The Court further clarified that standing and “party concerned” status under § 256(b) are distinct legal concepts with different requirements.

The Federal Circuit also rejected Fortress’ characterization of § 256(b) as a broadly permissive “savings provision,” explaining that the statute only operates to save patents once its procedural prerequisites of notice and an opportunity to be heard are satisfied.

Turning to Fortress’ second argument, the Federal Circuit concluded that a patent that incorrectly lists its inventors and cannot be corrected under § 256 has a clear statutory basis for invalidity. Reading § 256(b) together with §§ 101 and 100(f), the Court concluded that when an invention has multiple inventors, all must be named. Allowing a patent to survive with only some inventors listed would render § 256’s corrective framework meaningless.

Practice note: The decision underscores the importance of accurate inventorship determinations and the practical risk that patents may be rendered invalid if an omitted inventor cannot be located and statutory correction requirements cannot be met.



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