CAFC Affirms JMOL Post-Verdict Reversal and Claim Term Elaboration in Magnolia v. Kurin
Panel Addresses Structural Separability and § 112(f)
The intersection of patent claim construction and physical device design frequently generates intense litigation. The recent decision in Magnolia Medical Technologies, Inc. v. Kurin, Inc., 2024-2001 (Fed. Cir. Mar. 6, 2026), highlights the severe consequences of utilizing separate structural terms to describe a multi-functional component—an issue that is usually better articulated and disputed early in trial.
The United States Court of Appeals for the Federal Circuit addressed two distinct questions of claim interpretation. The first issue involved whether separately listed claim elements inherently demand separate physical components. The second issue focused on the application of means-plus-function claiming rules to generic terms lacking the word “means.”
Beyond the relatively mundane claim construction issues, the timing of the lower court’s ruling stands out as rather unique. The Federal Circuit affirmed the district court judgment—a JMOL decision that reversed a jury finding of infringement—and permitted an alleged late-game change in claim construction as an “elaborat[ion]” to the plain and ordinary meaning.
The appellate panel confirmed that separately recited limitations generally require distinct corresponding structures. The court agreed that the term “diverter” failed to supply sufficient structural definiteness, subjecting the claim to 35 U.S.C. § 112(f).
Background of the Dispute
The technology underlying this dispute addresses a persistent challenge in medical diagnostics. Medical practitioners routinely draw blood to test for pathogenic microbes. Skin microbes frequently dislodge during the initial needle insertion and contaminate the blood sample. Such contamination yields false-positive test results. Patients then receive unnecessary anti-microbial therapies.
To remedy this issue, inventors developed blood sequestration devices. These devices sequester the initial portion of the collected blood, keeping potential contaminants away from the primary testing sample (Slip Op., pp. 3-6).
Magnolia Medical Technologies, Inc. holds two patents covering such devices: U.S. Patent 10,039,483 (the ‘483 patent) and U.S. Patent 9,855,001 (the ‘001 patent). Claim 1 of the ‘483 patent describes a blood sequestration device featuring “a fluid reservoir... at least partially defined by a seal member” and “a vent... configured to allow air to exit the housing as blood enters the fluid reservoir” (p. 12). Claim 1 of the ‘001 patent claims an apparatus with “a diverter having an inlet, a first outlet... and a second outlet” (p. 15).
The accused product, the Kurin Lock, relies on pressure differences to divert the initial flow of blood. Blood enters the device and meets a junction leading to a sample channel and a U-shaped side channel. The U-shaped side channel features a “porous plug” made of absorbent material (p. 5). When dry, the porous plug permits air to escape into the atmosphere. The open pathway creates a path of least resistance for the incoming blood. The initial blood draw fills the U-shaped channel. Upon contact with the liquid blood, the porous plug expands. The expanded material shuts the pores and blocks further airflow. The path of least resistance shifts to the sample channel, directing the remaining, uncontaminated blood into a collection bottle (pp. 5, 6).
Magnolia sued Kurin in the United States District Court for the District of Delaware. For the ‘001 patent, the district court construed “diverter” as a means-plus-function term. The parties then stipulated to non-infringement on the ‘001 patent. The litigation on the ‘483 patent proceeded to a jury trial. The jury found infringement.
Kurin filed a post-trial motion for judgment as a matter of law (JMOL). The district court granted the motion. The district judge determined the Kurin Lock could not infringe as a matter of law. The district court reasoned that the ‘483 patent required separate structures for the “vent” and the “seal,” but the accused device relied on a single component to perform both roles. Magnolia appealed the ruling.
Delayed Claim Construction?
For the ‘483 patent, the central legal conflict involved the timing and substance of the district court’s claim construction. Magnolia argued the district judge adopted an untimely, new claim construction post-verdict by determining the “vent” and “seal” limitations required distinct physical structures.
At trial, the jury received instructions to apply the plain and ordinary meaning of the terms. The Federal Circuit addressed this timing argument directly, distinguishing between an impermissible new construction and a permissible clarification:
“We disagree. Indeed, Magnolia is correct that where parties agree that the plain and ordinary meaning of a claim term applies, it is improper for the district court to adopt a materially different claim construction at JMOL. See Hewlett-Packard Co. v. Mustek Sys., Inc., 340 F.3d 1314, 1321 (Fed. Cir. 2003) (‘It is too late at the JMOL stage to . . . adopt a new and more detailed interpretation of the claim language and test the jury verdict by that new and more detailed interpretation.’). But, it is permissible for a district court to ‘elaborate’ on its construction post-verdict when it ‘only clarifies what was inherent in the construction.’ Cordis Corp. v. Bos. Sci. Corp., 658 F.3d 1347, 1356 (Fed. Cir. 2011). We conclude that the district court engaged in such permissible clarification here” (p. 10).
Separate Structures
The Federal Circuit rejected the procedural argument presented by Magnolia. Relying on the precedent established in Becton, Dickinson & Co. v. Tyco Healthcare Group, LP, the appellate court affirmed that the district judge merely clarified the inherent plain meaning of the claim.
The panel pointed out the structural phrasing of claim 1 and that listing the two limitations separately, connected with the word “and,” implies separate structures. The specification supported this interpretation by describing the seal and vent as distinct physical components.
The appellate court concluded:
Here, claim 1 uses the transitional phrase “comprising,” and both the “vent” and “seal” limitations are preceded by the word “a,” see ’483 patent col. 20, ll. 52–57, meaning that one or more of each structure is required in the patented invention. Elkay 192 F.3d at 977; see also Becton, 616 F.3d at 1254 (separate-structure implication applied even though second structure not preceded by “a”).[]
Second, just as in Becton, the two limitations are connected by the word, “and,” suggesting that the “vent” structure is in addition to, i.e., separate, from the “seal” structure. ’483 patent col. 20, ll. 52–58. Nothing in the text of claim 1 is to the contrary. Becton, 616 F.3d at 1255 (“There is nothing in the asserted claims to suggest that the two separately listed limitations can be the same structure.”). (pp. 12-13).
The Kurin Lock apparently utilizes a single structure—the porous plug—to perform both the venting function and the sealing function. Prior to contact with the fluid, it acts as a vent. Following expansion, it acts as a seal (p. 6).
Upon the motion for judgment as a matter of law (JMOL), the court found that lack of two separate structures in the accused product precluded a finding of infringement by the jury.
Means-Plus-Function
Regarding the ’001 patent, the legal issue centered on overcoming the presumption against means-plus-function claiming. The term “diverter” does not contain the word “means.” The law dictates a challenger must demonstrate the term fails to recite sufficiently definite structure to invoke 35 U.S.C. § 112(f). The parties agreed the function of the diverter was to direct bodily fluid down one of two paths.
The court analyzed the structural recitations in claim 1. The claim describes an inlet and two outlets. The appellate panel determined these elements operate passively. They receive and facilitate fluid flow. They do not actively direct the fluid down one path or the other. The structural elements alone proved insufficient to perform the stated function without additional mechanisms.
The Federal Circuit found strong support for this conclusion in the testimony of Magnolia’s own expert. The expert stated a person of ordinary skill would understand a diverter to include “at least one inlet and two outlets branches” (p. 18).
The court interpreted this statement as a fatal admission. The testimony confirmed “diverter” acts as a generic term capturing any structure performing the function, rather than a definite structural name. The panel affirmed the application of 35 U.S.C. § 112(f). The court stated:
“The ‘essential inquiry is not merely the presence or absence of the word “means” but whether the words of the claim are understood by persons of ordinary skill in the art to have a sufficiently definite meaning as the name for structure.’” (p. 17).
Key Takeaways and Practical Implications
This decision carries some weight for patent practitioners drafting and litigating device claims. The ruling reinforces the doctrine of structural separability. Drafting attorneys must approach the listing of claim elements with extreme care. Separating functional roles into distinct structural nouns—like “a vent” and “a seal”—creates a strong legal presumption.
The law will presume the invention requires distinct physical components. When a single physical component serves multiple functions, patent claims should explicitly describe that single-component embodiment. Relying on generic transitional phrases will not save a claim from the separability doctrine.
Litigators must evaluate their infringement theories early in the process. Relying on the “plain and ordinary meaning” of a claim carries inherent risks. A trial judge retains the authority to clarify the inherent structural requirements of a claim even after a jury verdict.
Litigants planning to argue that a single accused component meets multiple separately listed claim limitations should request an explicit claim construction prior to trial. Waiting for the JMOL stage leaves the verdict highly vulnerable.
The requirement to define distinct structural components presents a significant hurdle during the drafting phase. Attorneys often attempt to capture broad subject matter by using expansive, functional language. The Magnolia decision illustrates the vulnerability of this approach. An over-reliance on functional outcomes without detailing the corresponding physical architecture creates immediate risk during enforcement.
For businesses managing intellectual property portfolios, this appellate decision necessitates a thorough review of existing assets. Claims previously considered broad enough to cover competing products might require reassessment.
A competitor adopting a streamlined, single-component design might successfully avoid infringement of a patent claiming multiple separate components. Securing durable patent protection demands a rigorous alignment between the drafted claim language and the physical realities of the mechanical design. Using continuation applications to cover alternative embodiments and plug design-around-gaps is a must.
The treatment of the ‘001 patent serves as a another warning regarding functional claiming. Patent drafters frequently use generic nouns like “diverter,” “mechanism,” or “element” to describe mechanical actions. The Federal Circuit continues to strictly apply the Williamson standard. Naming passive components, such as inlets and outlets, fails to provide sufficient structure for an active function. Practitioners must describe the physical mechanism performing the action within the claim text.
Failing to provide structural details invites a § 112(f) construction. Such a construction limits the claim scope exclusively to the specific embodiments described in the specification, making it exceedingly difficult to capture competing designs achieving the same result through different physical methods.
Conclusion
Magnolia Medical Technologies, Inc. v. Kurin, Inc. provides a solid examination of claim drafting mechanics, but it also offers a sobering lesson in litigation strategy.
It is one thing to say that the court knows better what the “plain and ordinary” meaning of a claim term is, e.g., at the Markman stage. It is another thing to withhold such information from the parties and jury until the end. That does not feel like justice. If there are more facts, the panel
Unless there is a much deeper record—as there often is in litigation—the procedural facts as relayed from the panel suggest that the precise infringement narrative and the corresponding structural arguments must not have fully crystallized for the participants until late in the trial process. The alternative might mean the court purposely sandbagged the parties with a secret “elaborate” claim construction knowing that the vent and seal had to be distinct elements. That’s not an efficient use of the justice system.
More importantly, the dismissal of a jury verdict serves as a frightening reminder of the inherent volatility of patent litigation. Even assuming the district judge arrived at the correct legal conclusion regarding structural separability, the timing of that realization is unsettling.
This procedural unpredictability forces patent owners to ask a difficult question: at what point is a settlement appropriate, even when a plaintiff appears to be winning before a jury?
The Federal Circuit demonstrated strict adherence to the structural implications of claim text organization, highlighting the boundaries of plain meaning and the persistent vulnerability of functional claim language.
Patent prosecution strategies must adapt to these stringent structural requirements, as the tension between functional claiming, structural separation, and procedural timing remains a defining—and highly risky—characteristic of intellectual property law.
Still, no one will be surprised when an examiner points to a single element of a prior art reference as anticipating two elements (e.g., a vent and a seal) in the near future, even if such practice is precluded for infringement.
Disclaimer: This is provided for informational purposes only and does not constitute legal or financial advice. To the extent there are any opinions in this article, they are the author’s alone and do not represent the beliefs of his firm or clients. The strategies expressed are purely speculation based on publicly available information. The information expressed is subject to change at any time and should be checked for completeness, accuracy and current applicability. For advice, consult a suitably licensed attorney and/or patent professional.