Technology & Information Law Blog by Charles Gideon Korrell

Tag: Indefiniteness

  • Enviro Tech v. Safe Foods: Federal Circuit Invalidates “About” pH Range Claims as Indefinite

    Enviro Tech v. Safe Foods: Federal Circuit Invalidates “About” pH Range Claims as Indefinite

    The Federal Circuit’s decision in Enviro Tech Chemical Services, Inc. v. Safe Foods Corp., Case No. 24-2160 (Fed. Cir May 4, 2026), adds another important chapter to the growing body of indefiniteness law applying Nautilus to “terms of approximation” such as “about,” “approximately,” and “substantially.” In a precedential opinion authored by Judge Lourie, the court affirmed invalidation of patent claims directed to poultry-processing methods because the patent failed to provide objective guidance regarding the permissible variance associated with the claimed pH range of “about 7.6 to about 10.”

    The decision is notable because the Federal Circuit did not hold that the word “about” is inherently indefinite. To the contrary, the panel reaffirmed decades of precedent recognizing that approximation language can be appropriate in patent claims. The problem for Enviro Tech was that its specification and prosecution history pointed in multiple directions, leaving a skilled artisan without reasonable certainty regarding the claim boundaries.

    For patent prosecutors and litigators, the opinion provides a practical warning: when a numerical range becomes important for patentability over prior art, vague approximation language may not survive scrutiny unless the intrinsic record clearly defines the permissible tolerance.

    Charles Gideon Korrell notes that the case is particularly important for chemical, pharmaceutical, and biotechnology patents, where words like “about” are frequently used to accommodate experimental variability and manufacturing tolerances.

    The Technology and Claimed Invention

    Enviro Tech’s U.S. Patent No. 10,912,321 concerned methods for treating poultry carcasses with peracetic acid during processing. The patent purported to improve poultry weight retention during processing by adjusting the pH of the antimicrobial solution to a more alkaline range.

    Representative claim 1 required adjusting the pH of the peracetic acid-containing water “to a pH of about 7.6 to about 10 by adding an alkaline source.”

    Safe Foods challenged the claims as indefinite under 35 U.S.C. § 112(b), arguing that the terms “about” and “an antimicrobial amount” failed to provide reasonable certainty regarding claim scope. The district court agreed as to both terms and invalidated the asserted claims.

    On appeal, the Federal Circuit affirmed based solely on the indefiniteness of “about,” declining to reach the separate issue concerning “antimicrobial amount.”

    The Federal Circuit’s Indefiniteness Framework

    The panel began with the familiar Nautilus standard, explaining that claims are indefinite if, when read in light of the specification and prosecution history, they fail to inform skilled artisans “with reasonable certainty” about the scope of the invention.

    The court relied heavily on prior Federal Circuit decisions addressing words of approximation, including:

    Those cases collectively establish that terms like “about” are not automatically valid or invalid. Instead, the acceptability of approximation language depends on whether the intrinsic and extrinsic evidence provide objective guidance regarding the range of acceptable deviation.

    The Federal Circuit emphasized that the permissible scope of “about” depends on the “technological facts of the particular case.”

    That principle has existed for decades, but Enviro Tech demonstrates that courts are increasingly willing to scrutinize whether the patent actually provides workable boundaries.

    The Claims Provided No Objective Guidance

    The panel first examined the claim language itself. Claim 1 required a pH “of about 7.6 to about 10,” but the claims never explained how far below 7.6 or above 10 the solution could deviate while still falling within the claim scope.

    Both parties agreed that “about” meant “approximately,” but the court concluded that substituting one vague term for another solved nothing. The opinion quoted Interval Licensing for the proposition that a claim remains indefinite if a skilled artisan cannot translate the language into “meaningfully precise claim scope.”

    This portion of the opinion reflects a broader post-Nautilus trend. Courts increasingly require objective anchors for subjective or approximation language. Merely invoking industry understanding or ordinary meaning is often insufficient unless the patent itself provides workable standards.

    The Specification Hurt More Than It Helped

    The specification proved especially damaging to Enviro Tech because it contained inconsistent examples regarding acceptable pH deviations.

    Many examples suggested that deviations of 0.3 pH units or less were acceptable. In several experiments, Enviro Tech adjusted the pH when the measured value differed from the target by more than 0.3.

    But the specification also included important exceptions. Some experiments continued despite deviations greater than 0.3.

    One particularly significant experiment involved processing 5.8 million chickens in a commercial poultry-processing plant while tolerating deviations between 0.35 and 0.5 pH units.

    The Federal Circuit considered that example highly informative because the patent’s objective was commercial-scale poultry processing. The large-scale industrial example therefore undermined any argument that 0.3 represented a meaningful boundary.

    The court ultimately concluded that the specification’s “conflicting guidance” failed to provide reasonable certainty regarding the meaning of “about.”

    Charles Gideon Korrell believes this aspect of the opinion is particularly important because it illustrates a recurring drafting problem: patentees often include numerous experimental examples without considering whether those examples establish conflicting implicit claim boundaries.

    In some circumstances, more examples improve enablement and written description support. But in Enviro Tech, the additional examples effectively created internal contradictions about the permissible tolerance range.

    The Prosecution History Was Equally Problematic

    The prosecution history also undermined Enviro Tech’s position.

    The Federal Circuit observed that Enviro Tech treated “about” inconsistently during prosecution. In one argument distinguishing prior art, Enviro Tech referred to “pH 7.6” without using “about.” Yet in another argument on the next page, it referred to “about 8 to about 9.”

    The court concluded that the applicant never explained what “about” meant and treated the term inconsistently throughout prosecution.

    Relying on Infinity Computer Products v. Oki Data Americas, the panel explained that inconsistent prosecution statements can contribute to indefiniteness when the claims and specification already leave uncertainty unresolved.

    Enviro Tech attempted to salvage the claims by arguing that its amendment from “about 7.3” to “about 7.6” implicitly established a 0.3-unit permissible variance.

    The court rejected that theory because the amendment was not accompanied by any explanatory remarks defining the scope of “about.”

    That discussion underscores another important prosecution lesson: if approximation language matters to patentability, practitioners should consider explicitly defining the intended tolerance during prosecution rather than relying on inference.

    The Prior Art Proximity Mattered

    Perhaps the most striking part of the opinion appears near the end, where the court explained that the proximity of the prior art heightened the need for precision.

    The panel noted that the prior art disclosed pH values as close as 7.0, while the claims were amended to require “about 7.6.”

    The court then delivered the opinion’s key takeaway:

    “The prior art is almost ‘about’ a pH of 7.6.”

    That sentence will likely appear in future indefiniteness briefing for years.

    The Federal Circuit effectively recognized a practical relationship between indefiniteness and patentability. When an applicant narrows a numerical range to avoid close prior art, approximation language cannot remain untethered and vague. The narrower the distinction over the prior art, the greater the need for objective claim boundaries.

    Charles Gideon Korrell notes that this reasoning may become increasingly important in crowded technology areas where patentability often turns on relatively small numerical differences.

    Relationship to Other Recent Federal Circuit Decisions

    The decision fits within a broader trend of Federal Circuit scrutiny toward subjective and flexible claim language.

    The court’s reasoning closely resembles recent cases requiring objective standards for terms of degree, including:

    What distinguishes Enviro Tech is the court’s detailed focus on internal inconsistencies within the specification itself. The patent did not fail because it lacked examples. It failed because the examples suggested multiple competing answers.

    That creates a difficult drafting tension for patent prosecutors. Rich experimental disclosures can strengthen enablement and written description support, but they can also unintentionally create ambiguity regarding claim scope.

    Practical Drafting Lessons

    The decision offers several practical lessons for prosecutors and litigators:

    1. Define Approximation Terms Explicitly

    If “about” is intended to permit a particular tolerance range, the specification should say so directly.

    2. Avoid Conflicting Experimental Standards

    Examples should consistently reflect the intended claim boundary. Multiple tolerance conventions may later be characterized as evidence of indefiniteness.

    3. Be Careful When Narrowing Around Prior Art

    Approximation language becomes more vulnerable when claims are amended to avoid closely neighboring prior art.

    4. Create a Clear Prosecution Record

    If approximation language matters, prosecution remarks should explain the intended scope and permissible variance.

    5. Consider Whether “About” Is Necessary

    In some situations, practitioners may be better served by reciting explicit tolerance ranges or measurement error margins instead of relying on open-ended approximation terms.

    Charles Gideon Korrell believes the opinion may encourage prosecutors to rely more heavily on expressly defined tolerances rather than generic modifiers like “about” or “approximately,” particularly in chemical and life sciences applications.

    Conclusion

    Enviro Tech v. Safe Foods reinforces that approximation language survives only when the intrinsic record provides objective guidance regarding claim scope. The Federal Circuit did not reject “about” categorically. Instead, it held that the patent’s claims, specification, and prosecution history collectively failed to establish a reasonably certain boundary.

    The decision also highlights a recurring post-Nautilus theme: ambiguity created during drafting and prosecution can become fatal when a patent later relies on flexible language to distinguish close prior art.

    For patent practitioners, the case serves as a reminder that words of approximation require careful support, consistent treatment, and clear objective boundaries. Otherwise, the effort to preserve flexibility may ultimately destroy enforceability altogether.

    By Charles Gideon Korrell

    Here is my coverage of the Nautilus case.

  • Gramm v. Deere: Reversal of Indefiniteness Finding for Means-Plus-Function Claim

    Gramm v. Deere: Reversal of Indefiniteness Finding for Means-Plus-Function Claim

    The Federal Circuit’s decision in Gramm v. Deere & Co., No. 24-1598 (Fed. Cir. Mar. 11, 2026) addresses a recurring issue in patent litigation: when a means-plus-function claim is sufficiently supported by corresponding structure in the specification. The case arises from agricultural technology used to maintain the proper height of a crop-harvesting header as the machine moves across uneven terrain. While the technology itself is specialized, the court’s reasoning has broader implications for how courts analyze indefiniteness under 35 U.S.C. § 112 when claims invoke § 112(f).

    The Federal Circuit ultimately reversed the district court’s ruling that the patent claims were indefinite. The opinion provides an instructive reminder that courts must identify the correct corresponding structure before concluding that a claim lacks sufficient disclosure.

    Background of the Dispute

    The patent at issue, U.S. Patent No. 6,202,395, is directed to an apparatus for maintaining a crop harvester’s header at a desired height above the soil. Maintaining consistent header height is critical in agricultural harvesting operations because uneven terrain can cause the header to either dig into the ground or miss portions of the crop.

    Richard Gramm is the inventor and owner of the ’395 patent, which is exclusively licensed to Reaper Solutions LLC (formerly Headsight). Reaper brought suit against Deere & Company alleging that Deere’s header sensor kits infringed the patent.

    The litigation has a long procedural history. Deere challenged the patent through inter partes review proceedings, after which only independent claim 12 and certain dependent claims remained in the case. The dispute then returned to district court, where the central issue became claim construction of the limitation “control means.”

    Both parties agreed that “control means” is a means-plus-function limitation governed by § 112(f). Under that provision, the claim is construed to cover the corresponding structure described in the specification and equivalents thereof.

    The dispute centered on whether the specification disclosed adequate structure for performing the claimed function.

    The District Court’s Indefiniteness Ruling

    The district court concluded that the claim was indefinite.

    In reaching that conclusion, the court first determined that the claimed function was performed by a general-purpose computer or controller. Under Federal Circuit precedent, when a means-plus-function limitation is implemented using a computer, the specification must typically disclose an algorithm for performing the claimed function.

    This principle stems from cases such as WMS Gaming Inc. v. International Game Technology, which held that a general-purpose computer is not sufficient structure unless the patent also discloses the algorithm that the computer performs. Similarly, the Federal Circuit’s en banc decision in Williamson v. Citrix Online, LLC reaffirmed that the absence of such disclosure can render a claim indefinite.

    Applying this framework, the district court held that the ’395 patent failed to disclose the required algorithm. As a result, the court determined that the “control means” limitation lacked sufficient corresponding structure and declared the claims indefinite under § 112(b).

    The district court entered judgment of invalidity in favor of Deere.

    The Federal Circuit’s Reversal

    The Federal Circuit reversed the indefiniteness ruling.

    Judge Reyna, writing for the panel, concluded that the district court had misidentified the relevant corresponding structure. Because that structural analysis was flawed, the indefiniteness determination could not stand.

    The Federal Circuit emphasized a key principle in means-plus-function analysis: the court must identify the structure disclosed in the specification that performs the claimed function. If at least one embodiment provides sufficient structure, the claim is not indefinite.

    This rule traces back to Cardiac Pacemakers, Inc. v. St. Jude Medical, Inc., where the Federal Circuit held that a claim remains valid even if only one disclosed embodiment provides the required corresponding structure.

    In Gramm, the specification referenced a system known as “Dial-A-Matic Version #1.” The Federal Circuit concluded that this system constituted the corresponding structure for the claimed “control means.”

    The district court had excluded Dial-A-Matic Version #1 from its structural analysis because the system lacked certain capabilities described elsewhere in the specification. Specifically, the district court believed the structure needed to perform additional functions beyond those recited in the claim.

    The Federal Circuit rejected that reasoning.

    The court explained that the corresponding structure must perform the claimed function—nothing more. If the specification describes additional capabilities or features, those extra functions should not disqualify the disclosed structure.

    By improperly narrowing the set of permissible structures, the district court had effectively eliminated the very embodiment that satisfied the means-plus-function requirement.

    Because Dial-A-Matic Version #1 was adequately disclosed and performed the claimed function, the Federal Circuit held that the “control means” limitation was not indefinite.

    The Algorithm Requirement in Context

    One of the more interesting aspects of the opinion is how it addresses the algorithm requirement for computer-implemented means-plus-function claims.

    In cases like WMS Gaming, the Federal Circuit held that a patent must disclose the algorithm executed by a computer performing the claimed function. Otherwise, the claim effectively covers any computer capable of performing the function, which would exceed the permissible scope of § 112(f).

    However, Gramm illustrates that the algorithm requirement does not apply rigidly in every situation. If the specification identifies a concrete physical system that performs the claimed function, that system itself may qualify as the corresponding structure.

    The key analytical step is determining whether the structure is merely a generic computer or whether it represents a specific system disclosed in the patent.

    Here, the Federal Circuit treated the Dial-A-Matic system as a sufficiently concrete structure to satisfy the statutory requirement.

    Standard of Review

    The court also reiterated the standards governing appellate review of claim construction and indefiniteness determinations.

    Questions involving intrinsic evidence—such as whether a claim invokes § 112(f) or whether the specification discloses corresponding structure—are reviewed de novo. However, underlying factual determinations based on extrinsic evidence are reviewed for clear error.

    This framework derives from the Supreme Court’s decision in Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., which established that subsidiary factual findings during claim construction receive deferential review.

    In this case, the Federal Circuit determined that the district court’s legal analysis of corresponding structure was incorrect, making reversal appropriate.

    Implications for Patent Drafting and Litigation

    The Gramm decision highlights several practical lessons for patent practitioners.

    First, the case underscores the continuing significance of means-plus-function claiming. Although many practitioners avoid § 112(f) language due to its structural limitations, such claims remain common in mechanical and control-system technologies.

    Second, the decision reinforces that the corresponding structure analysis must be anchored to the claimed function—not to broader descriptions in the specification.

    Third, the opinion illustrates the importance of clearly describing operational systems in the specification. Even when a patent does not explicitly recite an algorithm, identifying a concrete system that performs the function may suffice.

    As Charles Gideon Korrell observes, disputes over indefiniteness frequently arise not because the patent lacks technical disclosure, but because courts and litigants disagree about which portions of the specification qualify as corresponding structure.

    Charles Gideon Korrell notes that the Federal Circuit’s reasoning in Gramm reflects a broader pattern in recent decisions: appellate courts are often skeptical of invalidity rulings that stem from overly restrictive structural interpretations.

    Another takeaway is that litigants should carefully evaluate whether the accused infringer’s own arguments about claim construction implicitly identify the corresponding structure. In Gramm, Deere had previously pointed to Dial-A-Matic Version #1 as a relevant system during claim construction, a position that ultimately undermined the indefiniteness theory.

    As Charles Gideon Korrell explains, this type of litigation posture can be significant because statements made during claim construction frequently shape how courts later evaluate indefiniteness.

    Finally, the decision reinforces the Federal Circuit’s long-standing principle that claims should not be invalidated lightly when the specification discloses at least one workable embodiment.

    Conclusion

    The Federal Circuit’s ruling in Gramm v. Deere provides a careful clarification of the corresponding-structure requirement for means-plus-function claims. By reversing the district court’s indefiniteness determination, the court emphasized that the proper inquiry focuses on whether the specification discloses structure capable of performing the claimed function—not whether the structure includes additional features or capabilities.

    For practitioners, the case serves as another reminder that indefiniteness challenges under § 112 often turn on the precision of the structural analysis. When courts identify the correct embodiment in the specification, many purported indefiniteness problems disappear.

    Charles Gideon Korrell believes that the decision will likely be cited in future disputes involving control systems and legacy mechanical patents, where functional language is common but the disclosed structure may not resemble modern software-driven implementations.

    By Charles Gideon Korrell

  • Canatex Completion Sol’ns v. Wellmatics: When Judicial Claim Correction Saves Patent Claims from Indefiniteness

    Canatex Completion Sol’ns v. Wellmatics: When Judicial Claim Correction Saves Patent Claims from Indefiniteness

    The Federal Circuit’s November 12, 2025 decision in Canatex Completion Solutions, Inc. v. Wellmatics, LLC, No. 2024-1466, provides a clear and disciplined application of the court’s demanding doctrine of judicial claim correction. Reversing a district court’s finding of indefiniteness, the panel held that an obvious drafting error in a patent claim could and should be corrected through claim construction, notwithstanding the Patent Office’s refusal to issue a certificate of correction. The decision reinforces the narrow but vital role courts may play in preserving claim validity when intrinsic evidence leaves no reasonable doubt about the patentee’s intended meaning.

    The Patent and the Alleged Error

    Canatex owns U.S. Patent No. 10,794,122, which claims a releasable connection device used in oil and gas well operations. The device consists of two parts that lock together during normal operations but may be separated if the downhole portion becomes stuck. The claims consistently describe a “first part” positioned further downhole and a “second part” closer to the surface.

    Independent claims 1, 7, and 13 included language describing a locking piston that permits a “releasable engagement profile” to expand radially and “release the connection profile of the second part.” As written, that phrase lacked an antecedent basis and, more importantly, conflicted with the mechanical logic of the device described throughout the patent. Only the first part is described as having a “connection profile,” while the second part includes the engagement components that grip and release that profile.

    The district court concluded that this defect rendered the claims indefinite. In its view, the repeated use of the disputed phrase across the claims and specification suggested intentional drafting rather than a clerical error, and the court declined to correct the language through construction.

    The Federal Circuit’s Framework for Judicial Correction

    On appeal, the Federal Circuit applied the longstanding but exacting standard for judicial claim correction. That standard traces back to the Supreme Court’s decision in I.T.S. Rubber Co. v. Essex Rubber Co., 272 U.S. 429 (1926), which held that courts may correct obvious claim errors when doing so merely gives effect to the meaning intended by the applicant and understood by the examiner.

    Modern Federal Circuit cases have distilled that principle into a demanding test. Judicial correction is appropriate only where:
    (1) the error is evident from the face of the patent, as viewed by a skilled artisan;
    (2) the correction is not subject to reasonable debate based on the claims, specification, and prosecution history; and
    (3) the correction is limited to an obvious minor clerical or typographical error.

    The court emphasized that this doctrine is narrowly circumscribed to protect the public notice function of patent claims. Judicial correction determines what the claim has always meant, unlike PTO correction under 35 U.S.C. § 255, which operates prospectively and may alter claim scope.

    Error Evident on the Face of the Patent

    Applying the first prong, the panel found the error obvious. The claim language required release of a “connection profile,” yet nowhere introduced any such profile for the second part. Moreover, the notion that the second part’s engagement mechanism would release a component of the second part itself made no mechanical sense.

    The specification reinforced the conclusion. Figures consistently showed the connection profile on the first part, and one passage explicitly—but erroneously—referred to “connection profile 16 of second part 14,” even though the same paragraph and surrounding text identified that profile as belonging to the first part. To a skilled reader, this internal contradiction confirmed the presence of a drafting mistake rather than a substantive ambiguity.

    Only One Reasonable Correction

    The court also concluded that there was only one reasonable correction: replacing “second” with “first.” That change aligned the claims with the device’s structure, the specification’s descriptions, and the figures. Defendants’ proposed alternatives—such as inferring an undisclosed connection profile on the second part or altering other claim language to preserve the word “second”—were rejected as illogical or scope-altering.

    The court was particularly unpersuaded by arguments that the error was intentional because it appeared multiple times. Repetition, the panel explained, does not transform an obvious mistake into a deliberate choice, especially where the specification elsewhere makes the intended meaning unmistakable.

    PTO Denial Does Not Preclude Judicial Correction

    While the appeal was pending, Canatex sought a certificate of correction from the PTO. The Office denied the request, stating that the proposed correction would change claim scope. The Federal Circuit acknowledged the denial but found it irrelevant to the judicial correction analysis. The standards governing PTO correction and judicial construction are different, and the PTO’s refusal did not undermine the court’s conclusion that the claim language, properly understood, always meant “first part.”

    This aspect of the decision underscores an important practical point that Charles Gideon Korrell often emphasizes: the availability or denial of PTO correction does not foreclose judicial correction when intrinsic evidence compels a single interpretation. Courts remain the final arbiters of claim meaning in litigation.

    Distinguishing Chef America

    The panel carefully distinguished Chef America, Inc. v. Lamb-Weston, Inc., where the court refused to correct claims that required heating dough “to” a temperature that would burn it. In Chef America, the prosecution history suggested that the language might have been intentional, and multiple plausible interpretations existed. By contrast, the Canatex patent contained no prosecution history suggesting intent to distinguish between first and second parts in the manner defendants proposed.

    As Charles Gideon Korrell notes, Canatex narrows the reach of Chef America by reaffirming that hyperliteral claim construction gives way when intrinsic evidence leaves no room for reasonable debate about the patentee’s intent.

    Practical Implications

    The decision provides reassurance that patents will not be invalidated for indefiniteness where the error is mechanical rather than conceptual and where the intrinsic record speaks with one voice. At the same time, the court’s careful analysis preserves the high bar for judicial correction, ensuring that courts do not rewrite claims under the guise of interpretation.

    For litigants, Canatex highlights the importance of grounding correction arguments firmly in the claims, specification, and figures. For drafters, it is a reminder that even small drafting slips can invite expensive litigation, though not every mistake is fatal.

    Charles Gideon Korrell believes the case strikes an appropriate balance between protecting the public notice function of patents and avoiding forfeiture of valuable rights due to obvious clerical errors. Courts may correct, but only when correction is unavoidable.

    By Charles Gideon Korrell

  • Barrette Outdoor Living, Inc. v. Fortress Iron, LP: Prosecution Disclaimer in a Later Continuation Can Narrow an Entire Patent Family

    Barrette Outdoor Living, Inc. v. Fortress Iron, LP: Prosecution Disclaimer in a Later Continuation Can Narrow an Entire Patent Family

    On October 17, 2025, the Federal Circuit issued a detailed and consequential opinion in Barrette Outdoor Living, Inc. v. Fortress Iron, LP, affirming a judgment of non-infringement while also affirming the district court’s rejection of indefiniteness challenges. The case provides a clear reminder that arguments made during prosecution of a later-filed continuation application can narrow the scope of earlier-issued patents in the same family, even where those earlier patents were already granted and never amended.

    The decision is especially notable for its careful treatment of prosecution disclaimer across time, its distinction between examiner disagreement and applicant acquiescence, and its application of those principles to claim terms that appear, at least facially, to be broader than the disclaimed language. As Charles Gideon Korrell has observed in other contexts, this opinion underscores that prosecution arguments can be as dangerous as claim amendments, particularly in large patent families with overlapping claim language.

    Background and the Asserted Patents

    Barrette owns four related patents directed to fencing and railing assemblies that use sliding, pivoting connectors to attach pickets to rails. The patents share a common specification and trace back to a common parent application. The asserted patents include U.S. Patent Nos. 8,413,332; 8,413,965; 9,551,164; and 9,963,905. The claims generally recite connectors having “bosses,” “projections,” or similar protruding structures that engage holes in the pickets, allowing the pickets to pivot and slide relative to the rails.

    The accused products, Fortress’s Athens Residential fences, use connectors that employ non-integral fasteners. After claim construction, Barrette stipulated that it could not prove infringement under the district court’s construction, while Fortress stipulated that it could not prove indefiniteness. That procedural posture set the stage for a clean appeal on claim construction and indefiniteness.

    Claim Construction and the “Boss” Terms

    The central dispute on appeal concerned the meaning of “boss,” “projection,” and related terms. The district court construed these terms as limited to integral structures, and further concluded that they were fastener-less. Barrette challenged both aspects of that construction.

    The Federal Circuit agreed with Barrette on one point but not the other. First, the court rejected the district court’s conclusion that the specification clearly and unmistakably disclaimed bosses that use fasteners. Relying on Phillips v. AWH Corp., the court reiterated that patents often describe multiple advantages over the prior art and that claims should not automatically be limited to structures that achieve every disclosed advantage. Here, although the specification emphasized fast installation as one benefit of the invention, it also emphasized improved racking ability, which did not inherently require fastener-less connections. The intrinsic record did not support importing a fastener-less limitation into the claims.

    That conclusion, however, did not save Barrette’s infringement case.

    Prosecution Disclaimer and Integral Structures

    The decisive issue was prosecution disclaimer arising from statements made during prosecution of a later continuation application that issued as the ’075 patent. During that prosecution, the examiner rejected claims over the Sherstad reference, which disclosed a pivot pin assembly. In response, Barrette argued that Sherstad failed to disclose a “slip-together connection with the claimed integral boss,” distinguishing Sherstad’s use of a discrete pin member from Barrette’s claimed structure.

    The Federal Circuit held that this argument constituted a clear and unmistakable disclaimer of non-integral bosses. Importantly, the court rejected Barrette’s attempt to characterize the argument as ambiguous or ineffective simply because the examiner ultimately maintained the rejection and Barrette later canceled the claims. The focus of disclaimer analysis, the court emphasized, is what the applicant said, not whether the argument persuaded the examiner or was strictly necessary to secure allowance.

    The court distinguished Ecolab, Inc. v. FMC Corp. and Malvern Panalytical Inc. v. TA Instruments-Waters LLC, where examiner disagreement and applicant acquiescence rendered earlier narrowing arguments ambiguous. Here, the examiner did not disagree with Barrette’s characterization of its own claims. Rather, the examiner disagreed with Barrette’s characterization of the prior art. Nothing in the prosecution history suggested that Barrette’s description of its own invention was mistaken or withdrawn.

    As Charles Gideon Korrell notes, this distinction is critical. Examiner disagreement with claim scope may neutralize a disclaimer, but examiner disagreement with an applicant’s reading of the prior art does not.

    Temporal Reach of Disclaimer Across the Family

    Barrette also argued that statements made during prosecution of the later-filed ’075 patent could not limit the scope of earlier-issued patents such as the ’332 and ’965 patents. The Federal Circuit squarely rejected that argument, citing Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc. for the proposition that statements made during prosecution of related patents may be considered in construing common claim terms, regardless of whether the statements pre- or post-date issuance of the patent at issue.

    This aspect of the opinion reinforces a recurring theme in Federal Circuit jurisprudence: patent families rise and fall together when claim language and specifications are shared. Strategic arguments in one application can echo backward in time.

    Extending the Disclaimer to Related Terms

    Barrette attempted to limit the damage by arguing that even if “boss” was limited to integral structures, other claim terms—such as “projection,” “nub,” and “series of axles”—should retain broader meanings. The court was unpersuaded.

    As to “projection,” the court found forfeiture. Barrette had repeatedly argued before the district court that “boss” and “projection” were commensurate in scope, even characterizing “projection” limitations as “boss” terms in its Markman submissions. Having taken that position below, Barrette could not reverse course on appeal.

    With respect to “nub” and “series of axles,” the court acknowledged that these terms were narrower than “boss,” but concluded that narrowing did not help Barrette. If the broader term was limited to integral structures, then the narrower terms necessarily were as well. Thus, even assuming some error in the district court’s interchangeable-use analysis, the outcome remained the same.

    Indefiniteness: Sliding and “Causes”

    On cross-appeal, Fortress challenged the district court’s rejection of its indefiniteness arguments. Fortress contended that the “sliding” terms were functional and ambiguous, and that the claims failed to specify parameters such as force, friction, or degree of motion.

    The Federal Circuit disagreed. Applying Nautilus, Inc. v. Biosig Instruments, Inc. and Sonix Technology Co. v. Publications International, Ltd., the court emphasized that definiteness requires reasonable certainty, not mathematical precision. The claims and specification provided sufficient guidance by describing how pivoting of the pickets causes the connector to slide along the rail, and by illustrating those interactions in multiple figures.

    Similarly, the court rejected Fortress’s argument that the term “causes” was indefinite because not every act of pivoting necessarily resulted in sliding. The court held that Barrette’s explanation during prosecution merely clarified the causal relationship in context, and that a skilled artisan could ascertain the scope of the term with reasonable certainty.

    Practical Takeaways

    The Federal Circuit’s decision delivers several practical lessons.

    First, prosecution disclaimer remains a potent doctrine, and it applies with full force to arguments, not just amendments. Second, disclaimers can propagate across an entire patent family, even retroactively affecting earlier-issued patents. Third, examiner disagreement only matters if it clearly signals that the applicant’s narrowing characterization was incorrect and accepted as such by the applicant.

    Charles Gideon Korrell believes that this case will encourage applicants to think more carefully about whether an argument is truly worth making in a continuation application. In many cases, the safer course may be to amend claims explicitly or to draft continuation claims that clearly delineate different scopes, rather than relying on argumentative distinctions that may later become shackles.

    In the end, Barrette lost not because its invention lacked merit, but because its own words during prosecution narrowed its claims beyond repair. As patent families continue to grow larger and more complex, this decision serves as a sharp reminder: every prosecution argument is a potential legacy.

    By Charles Gideon Korrell

  • Fintiv, Inc. v. PayPal Holdings, Inc.: No Structure, No Claim — Payment Handler Terms Held Indefinite Under § 112 ¶ 6

    Fintiv, Inc. v. PayPal Holdings, Inc.: No Structure, No Claim — Payment Handler Terms Held Indefinite Under § 112 ¶ 6

    In Fintiv, Inc. v. PayPal Holdings, Inc., No. 23-2312 (Fed. Cir. Apr. 30, 2025), the Federal Circuit affirmed the Western District of Texas’s ruling that the asserted patent claims were invalid as indefinite. The decision underscores the court’s continued enforcement of 35 U.S.C. § 112 ¶ 6 for software-related terms that fail to recite sufficient structure, extending the line of cases exemplified by Williamson v. Citrix Online, LLC, 792 F.3d 1339 (Fed. Cir. 2015).

    Background

    Fintiv asserted four patents—U.S. Patent Nos. 9,892,386, 11,120,413, 9,208,488, and 10,438,196—relating to a cloud-based mobile transaction system. At issue were various claims referring to a “payment handler” or “payment handler service” that either (1) used APIs of various payment processors or (2) exposed a common API for interacting with them.

    The district court, applying § 112 ¶ 6, found the payment-handler terms to be means-plus-function limitations and held the claims indefinite for failure to disclose corresponding structure. Fintiv appealed.

    Key Holdings

    1. The Payment Handler Terms Invoke § 112 ¶ 6

    The Federal Circuit agreed with the district court that the “payment handler” and “payment handler service” terms were functional, lacked sufficient structural meaning, and thus invoked § 112 ¶ 6. Although these terms did not use the word “means,” the court found that the presumption against § 112 ¶ 6 was rebutted under Williamson, which allows application of § 112 ¶ 6 when a term “recites function without reciting sufficient structure for performing that function.”

    The panel emphasized that:

    • “Handler” is akin to “module,” a term previously found by the court to lack structural significance.
    • Appending the term “payment” did not supply structure but merely described a function.
    • Expert testimony indicated that a person of ordinary skill would not understand how to implement the recited functions based on the claim language alone.

    Fintiv’s reliance on Dyfan, LLC v. Target Corp., 28 F.4th 1360 (Fed. Cir. 2022), was unpersuasive. Unlike Dyfan, where unrebutted expert testimony supported structure, here neither party’s expert testified that “payment handler” connoted a definite structure.

    2. Lack of Corresponding Structure in the Specification

    Once § 112 ¶ 6 was triggered, the court found that the patents failed to disclose any algorithm or adequate structure for the “payment handler” functionality. Merely restating the claimed function—“wrap[ping] APIs” and “expos[ing] a common API”—did not meet the requirement.

    Citing Aristocrat Technologies Australia Pty Ltd. v. International Game Technology, 521 F.3d 1328 (Fed. Cir. 2008), and Rain Computing, Inc. v. Samsung Electronics America, Inc., 989 F.3d 1002 (Fed. Cir. 2021), the court reiterated that describing only a general-purpose computer without a specific algorithm is insufficient.

    Fintiv’s attempt to point to a supposed two-step algorithm was rejected as merely a restatement of the claim language. The court also dismissed the idea that the figures in the patents showed a structural implementation of the payment handler, noting a lack of clarity on how the functions were performed or how different APIs were integrated.

    Implications

    This decision adds to the growing body of Federal Circuit case law demanding structural specificity in software patent claims. Key takeaways include:

    • Terms that combine a generic function descriptor with a purpose (e.g., “payment handler”) are increasingly likely to be swept into § 112 ¶ 6 territory if not clearly supported by structural description.
    • Boilerplate specification language that simply mirrors claim terms without detailing implementation will not rescue functional claims.
    • Practitioners should be cautious in relying on software terms like “service,” “module,” or “handler” without anchoring them to known, sufficiently detailed structures or algorithms in the specification.

    Conclusion

    Fintiv v. PayPal reiterates that when it comes to software patents, claiming a function is not enough—patentees must disclose how the function is performed with sufficient specificity. This decision reinforces the Federal Circuit’s post-Williamson trajectory and continues the tightening of indefiniteness doctrine in the software space.

    By Charles Gideon Korrell

  • Patent Law and Drug Innovation: Federal Circuit Upholds Rejection of ImmunoGen’s Patent Application

    On March 6, 2025, the Federal Circuit issued its opinion in ImmunoGen, Inc. v. Stewart, affirming the district court’s ruling that denied ImmunoGen’s patent application for a dosing regimen of its antibody drug conjugate (ADC), IMGN853. The court’s decision, rooted in key principles of intellectual property law, particularly focused on the doctrines of indefiniteness and obviousness. This case highlights ongoing challenges in securing patents for pharmaceutical dosing regimens and underscores the high bar for patentability in the biotechnology sector.

    Background of the Case

    ImmunoGen sought a patent for a specific dosing regimen of IMGN853, a drug used to treat ovarian and peritoneal cancers. The key claim at issue involved administering IMGN853 at a dose of 6 milligrams per kilogram (mg/kg) of adjusted ideal body weight (AIBW). The U.S. Patent and Trademark Office (USPTO) rejected the application, a decision that was subsequently affirmed by the Patent Trial and Appeal Board (PTAB). ImmunoGen then pursued relief in the Eastern District of Virginia under 35 U.S.C. § 145, which allows applicants to challenge USPTO decisions in district court.

    Following a bench trial, the district court ruled against ImmunoGen, determining that the claimed invention was fatally indefinite, obvious in light of prior art, and unpatentable under the doctrine of obviousness-type double patenting. ImmunoGen appealed to the Federal Circuit, which affirmed the lower court’s ruling based on obviousness.

    Key Legal Issues

    1. Obviousness Under 35 U.S.C. § 103

    The Federal Circuit upheld the rejection of ImmunoGen’s patent claims on the grounds that they were obvious in light of prior art. The court applied the well-established Graham v. John Deere Co. framework, which requires assessing:

    • The scope and content of the prior art
    • Differences between the prior art and the claims at issue
    • The level of ordinary skill in the art
    • Any secondary considerations (such as commercial success or unexpected results)

    The court found that a person of ordinary skill in the art would have been motivated to try the claimed dosing regimen based on existing knowledge of ocular toxicity risks associated with ADCs, prior dosing methodologies, and available clinical data. The decision emphasized that AIBW was a known dosing methodology in the prior art, and adjusting dosage to reduce toxicity was a routine optimization.

    2. The Role of Prior Art in Determining Obviousness

    The court found that:

    • Existing literature disclosed IMGN853 and its dosing regimens based on total body weight (TBW).
    • Previous studies had explored adjusted dosing strategies (including AIBW) to reduce toxicity in related drug classes.
    • A person of ordinary skill in the art would have been able to transition from TBW to AIBW dosing as an obvious variation, especially since AIBW dosing had been previously used to reduce ocular toxicity for other drugs.

    Ultimately, because the claimed dose of 6 mg/kg AIBW was within the range of known effective doses, the court determined that the invention was a predictable result of routine experimentation rather than an unexpected innovation.

    3. Indefiniteness Under 35 U.S.C. § 112

    While the Federal Circuit did not rule on indefiniteness, the district court’s decision noted that the application failed to define AIBW adequately, leaving ambiguity in the claim’s scope. Courts require patent claims to be sufficiently clear so that a person of ordinary skill in the art can ascertain the precise bounds of the invention.

    The district court found that multiple formulas for AIBW existed, creating uncertainty about which formula applied to ImmunoGen’s claims. This contributed to the court’s ruling that the patent claims were fatally indefinite, making them unenforceable.

    4. Obviousness-Type Double Patenting

    The government also argued that the claims were unpatentable under the doctrine of obviousness-type double patenting, which prevents an inventor from obtaining multiple patents on obvious variations of the same invention. The district court found that ImmunoGen’s claims were largely duplicative of its previous patents, reinforcing the determination of obviousness. However, on appeal, both parties agreed that the double patenting issue rose and fell with the obviousness analysis, making further discussion unnecessary.

    Implications for the Biotechnology and Pharmaceutical Industries

    This decision underscores the high threshold for patentability in pharmaceutical dosing regimens. Courts have consistently ruled that dosing adjustments—particularly those based on well-known methodologies—are often seen as routine optimizations rather than true inventions. This presents significant challenges for drug developers seeking patent protection for new dosing strategies.

    Key takeaways from this case include:

    • Drug manufacturers must provide clear evidence of unexpected results to differentiate dosing regimen patents from routine experimentation.
    • Precision in claim drafting is critical to avoid indefiniteness challenges.
    • Applicants should consider alternative strategies, such as method-of-use claims tied to specific patient populations or therapeutic effects, to enhance patentability.

    Conclusion

    The Federal Circuit’s ruling in ImmunoGen, Inc. v. Stewart reinforces longstanding principles in patent law regarding obviousness and claim definiteness. While pharmaceutical innovators continue to seek patent protection for dosing regimens, this case demonstrates the difficulties of overcoming obviousness rejections, particularly where prior art provides clear guidance on dosage adjustments. Moving forward, companies seeking similar patents will need to present strong, non-obvious justifications to withstand legal scrutiny and secure valuable intellectual property protections.

    By Charles Gideon Korrell

  • Federal Circuit Overturns District Court’s Ruling on Indefiniteness in Teleflex v. Medtronic

    In a significant decision for medical device patent litigation, the Federal Circuit vacated and remanded a district court’s ruling that had invalidated key claims in a patent dispute between Teleflex and Medtronic. The case centered on guide extension catheter technology used in cardiovascular procedures, with the core issue being whether the term “substantially rigid portion/segment” was indefinite. The ruling provides important guidance on claim construction, functional limitations, and indefiniteness under patent law.

    Background of the Case

    Teleflex, along with its affiliates, sued Medtronic in the District of Minnesota for infringing seven patents related to guide extension catheters, which help deliver interventional devices into arteries. The patents describe a coaxial guide catheter with a substantially rigid portion that enables controlled movement within a standard guide catheter.

    The dispute boiled down to the meaning of “substantially rigid portion/segment”—a key term appearing in multiple claims across Teleflex’s patents. Medtronic argued that the term was indefinite because its boundaries varied across claims, making it impossible for a skilled artisan to determine its precise scope.

    The district court agreed with Medtronic, ruling that the inconsistency in claim boundaries made the term indefinite, effectively invalidating all asserted claims. Teleflex appealed, arguing that the court misapplied the law on claim construction and indefiniteness.

    Key Issues Addressed by the Federal Circuit

    1. Can the Boundary of a “Substantially Rigid Portion” Vary Across Claims?

    The district court ruled that all claims must define the substantially rigid portion in a consistent way, and since some claims included a side opening in the rigid portion while others placed it separately, the claims were “mutually exclusive” and thus indefinite.

    The Federal Circuit rejected this logic, clarifying that:

    • Independent claims do not need to define terms in exactly the same way across a patent.
    • Claim drafting often involves describing the same invention in different ways to cover variations in implementation.
    • The fact that some claims place the side opening within the rigid portion while others place it distal to it does not automatically create indefiniteness.

    2. Functional Claiming and the Meaning of “Substantially Rigid”

    Teleflex argued that “substantially rigid” should be interpreted as a functional limitation—meaning the portion of the catheter that is rigid enough to perform a specific function (i.e., advancing within the guide catheter).

    The Federal Circuit agreed, stating:

    • The term can be defined by its function rather than requiring an exact material or structural boundary.
    • Functional claiming is valid as long as it provides reasonable certainty about the claim’s scope.
    • The district court erred in insisting that all claims must define rigidity with the same fixed boundary.

    3. Role of Claim Construction in Indefiniteness Analysis

    The court emphasized that indefiniteness is a high standard and that:

    • A claim is only indefinite if it fails to inform skilled artisans with reasonable certainty about the scope of the invention (Nautilus, Inc. v. Biosig Instruments, Inc.).
    • Since experts and the Patent Trial and Appeal Board (PTAB) were able to interpret and apply the claims, the term could not be considered “insolubly ambiguous”.

    Thus, the Federal Circuit vacated the indefiniteness ruling, instructing the district court to reassess claim construction without treating the claims as inherently conflicting.

    Impact of the Decision

    This ruling has significant implications for medical device patents and functional claim drafting:

    • Claim Variability is Not Fatal: The decision reinforces that patent claims can define the same invention in different ways without necessarily being indefinite.
    • Functional Claiming Remains Viable: The court validated the use of functional limitations, allowing claims to describe components by what they do, rather than only by their structure.
    • Higher Bar for Indefiniteness: The ruling underscores that courts must apply a high standard before declaring a patent claim invalid due to indefiniteness.

    For patent litigators and medical device companies, this case serves as a reminder that precision in claim construction matters, but reasonable flexibility is allowed when defining key terms.

    By Charles Gideon Korrell

    Here’s a prior article written on the Nautilus case.