International Medical Devices, Inc. v. Cornell, No. 2025-1580 (Fed. Cir. Apr. 17, 2026)

The Federal Circuit reversed a substantial jury verdict and bench-trial damages award against a group of Texas urologists and their affiliates who were found to have misappropriated four trade secrets embodied in the Penuma cosmetic penile implant. Writing for a unanimous panel, Judge Dyk held that three of the asserted trade secrets (internal pockets to soften silicone, distal mesh tabs to promote tissue ingrowth, and absorbable sutures paired with mesh tabs) were generally known under California law because each had been disclosed in prior patents; that the fourth (the Penuma instrument list) had lost any secrecy when it was emailed to third parties without confidentiality restrictions; and that the same ideas that failed to qualify as trade secrets also failed to sustain a claim that plaintiff Dr. James Elist was a co-inventor of the defendants’ two patents. The court vacated roughly $17 million in reasonable-royalty and exemplary damages and a five-year permanent injunction, while affirming a $1 million statutory counterfeiting judgment tied to Dr. Cornell’s unauthorized use of the Penuma trademark.

The opinion is a useful teaching vehicle on the patent/trade-secret interface. It reinforces the familiar rule that ideas placed in the public domain through a patent disclosure cannot be reclaimed as trade secrets. It also articulates something of an obviousness rule for trade secrets: “no protectable trade secret results from translating a generally known concept from one environment to another environment where both environments present the same problem that is solved by the same solution.”

In most jurisdictions, the trade secrecy definition is limited to information “not being generally known to, and not being readily ascertainable through proper means by, another person …” 18 U.S.C. § 1839(3). But, California law – the law of this case – omits the “readily ascertainable” language its statutory definition of a trade secret.  Here, though the court found that the “generally known” standard absorbs much of the functional load.

The inventorship holding, grounded in Board of Education ex rel. Board of Trustees of Florida State University v. American Bioscience, Inc., 333 F.3d 1330 (Fed. Cir. 2003), illustrates how a finding that information is in the public domain for trade-secret purposes can ripple into patent validity by defeating a claim of inventive contribution.

Factual background. Dr. Elist, a Beverly Hills urologist, developed the Penuma, a silicone sleeve placed subcutaneously between the skin and Buck’s fascia. In 2018, the Penuma was the only commercially available cosmetic penile implant. Dr. Robert Cornell attended a Penuma surgical training on March 30, 2018, signed a non-disclosure agreement, and watched Dr. Elist perform several implant surgeries. At the training, Dr. Elist described three concepts for improving the implant: internal cavities within the silicone body to increase softness and elasticity; mesh tabs near the distal tip for tissue ingrowth; and absorbable sutures paired with the mesh tabs to hold the implant temporarily while ingrowth occurs. Shortly after the training, Dr. Cornell requested and received the Penuma instrument and supply list. Within months, Dr. Cornell and two colleagues filed patent applications that eventually matured into U.S. Patent Nos. 10,413,413 and 10,980,639, claiming cosmetic implant designs incorporating the three Elist-identified features. None named Dr. Elist as an inventor. Defendants launched a competing implant called Augmenta.

The jury found liability on all claims. After a bench trial, Senior Judge Consuelo Marshall awarded $5.77 million in reasonable royalties, $11.54 million in exemplary damages for willful and malicious misappropriation, $1 million in statutory counterfeiting damages under the Lanham Act, and a five-year permanent injunction. JMOL was denied.

The “generally known” analysis.  Generally information disclosed in a patent or published application cannot be a trade secret.  This case though focused on a slightly more nuanced question — what if the information was disclosed, but in a different framework or setting.  Here, several of the alleged trade secrets were disclosed in patents for therapeutic devices for treating erectile disfunction whereas the product here is a somewhat different field of aesthetic devices. The opinion rejected the distinction. The court first noted that “generally known” inquiry is “less granular” than the patent-law obviousness standard and serves the California policy of promoting and rewarding innovation.  Ultimately, the court reached the following rule:

No protectable trade secret results from translating a generally known concept from one environment to another environment where both environments present the same problem that is solved by the same solution.

In this case, it did not matter that the prior art patent disclosure had never been implemented in a commercial product. Likewise, there is no requirement that any party know if the existence of the prior art prior to litigation.

In DTSA cases, I would have thought of a published patent as “readily ascertainable.”  But the California statute does not have that provision and so the court was forced to decide whether a patent is “generally known” to persons in the field.  California plaintiffs have sometimes leveraged the narrower statutory definition to argue that published information may remain “not generally known” within a specific field.  Here though Judge Dyk’s use of adjunct-environments tells folks how to draw the line.  A patent disclosing a feature in a related field is likely to be treated as public-domain prior art against a trade-secret claim, even without a formal obviousness analysis.  Notably, this is much like the analogous arts test for patent law.

The instrument list. The fourth asserted trade secret failed was an ingredient list.  But, the plaintiff’s president conceded that the list had been emailed to a third-party surgical center without confidentiality markings, and the email to Dr. Cornell contained only generic boilerplate without specifically designating the list as confidential. The operative NDA contained no general provision covering all communications between the parties. Under these facts, no reasonable jury could find the list derived independent economic value from secrecy.  This holding follows the general rule across trade secret doctrine that unrestricted disclosure to third parties extinguish trade-secret status.

What about inventorship. The inventorship analysis required no new fact-finding. Plaintiffs argued Dr. Elist was a co-inventor of the ‘413 and ‘639 patents because he contributed the same three ideas asserted as trade secrets. Under BJ Services Co. v. Halliburton Energy Services, Inc., 338 F.3d 1368 (Fed. Cir. 2003), “each joint inventor must contribute in some significant manner to the conception of the invention.” A person who contributes only what is already known in the prior art does not contribute to conception. Eli Lilly & Co. v. Aradigm Corp., 376 F.3d 1352 (Fed. Cir. 2004). The same finding that defeated trade-secret protection defeated inventorship.

As part of the analysis here, the court noted particularly that the patent applicant had contributed a differential-hardness feature that the examiner recited as the patentable contribution of the invention. Dr. Elist had no role in adding that feature and so was unable to claim a significant contribution to what was ultimately claimed.  This case reinforces the idea that correct inventorship — especially in team environments — will depend upon what is eventually claimed.

The companion opinion, International Medical Devices, Inc. v. Cornell, Nos. 2025-1843 (Fed. Cir. Apr. 17, 2026) (nonprecedential), vacates the district court’s $589,343 costs award and dismisses plaintiffs’ cross-appeal for attorneys’ fees under Cal. Civ. Code § 3426.4 as moot in light of the reversal of the trade-secret judgment.

Director Squires signed an Official Gazette Notice on April 1, 2026, creating a new procedure that allows patent owners to file a 30-page paper arguing against the existence of a substantial new question of patentability (SNQ) before the USPTO decides whether to order ex parte reexamination. The procedure, effective for requests filed on or after April 5, 2026, gives patent owners a 30-day window after service of the reexamination request to submit their arguments, with no petition or fee required. Third-party requesters may respond only in limited circumstances, by petition (and fee), with a 10-page cap.

The Notice is the USPTO’s response to what it describes as a “recent increased volume of ex parte reexamination requests.” That volume increase is itself a direct consequence of Director Squires’ restriction of inter partes review, which has driven challengers toward ex parte reexamination as an alternative path.  And, as recently as March 25, 2025, Dir Squires testified to Congress that “there’s always reexamination” as a substitute for the reduced availability of IPR and PRG procedures.

As a practical matter, the new procedure is welcome for patent owners. It gives them a front-end opportunity to persuade the Office that a reexamination request should be denied before it becomes a proceeding. Under prior practice, the patent owner’s first opportunity to respond came only after the Office had already found an SNQ and ordered reexamination. The pre-order paper lets patent owners frame the SNQ issue at the threshold, which is far less costly than defending through a full reexamination.

Sidebar: Ex Parte Reexamination Basics. Under 35 U.S.C. 302, any person may request reexamination of a patent based on prior art patents or printed publications. The USPTO Director must determine within three months whether the request raises a "substantial new question of patentability" (SNQ) under 35 U.S.C. 303(a). If an SNQ is found, reexamination is ordered, and the patent owner may file a statement under 37 CFR 1.530. The proceeding then continues as an examination between the patent owner and the USPTO, with the third-party requester having no further participation beyond a single reply to the patent owner's statement.

But there is a doctrinal problem with how the USPTO is implementing this change. It is well established that agencies are bound by their own regulations until those regulations are properly amended. See, e.g., Accardi v. Shaughnessy, 347 U.S. 260 (1954); Service v. Dulles, 354 U.S. 363 (1957). The usual path for changing a regulation is notice-and-comment rulemaking under the Administrative Procedure Act. 5 U.S.C. 553.

Two existing regulations stand directly in the way of the new procedure. 37 CFR 1.530(a) states that “no statement or other response by the patent owner in an ex parte reexamination proceeding shall be filed prior to” the SNQ determination, and directs that any premature filing “will not be acknowledged or considered in making the determination, and it will be returned or discarded.” 37 CFR 1.540 likewise provides that no submissions beyond those specified in the post-order sequence “will be considered prior to examination.”

Rather than amending these rules through notice-and-comment rulemaking, the Director is waiving them under 37 CFR 1.183, which permits the Director to suspend or waive regulatory requirements “in an extraordinary situation, when justice requires.” The Notice identifies the extraordinary situation as the increased volume of reexamination requests. The Notice then states that “[s]hould the pre-order papers prove helpful, the Office will consider revisions to the rules.” That concession suggests the Office recognizes the waiver is a stopgap rather than a permanent legal foundation.

Obviousness is the most litigated doctrine in patent law, but I have always seen the analytical framework as having a hole in the middle. The Supreme Court’s 1966 decision in Graham v. John Deere Co., 383 U.S. 1 (1966), directs courts and examiners to evaluate four sets of facts when deciding whether a claimed invention would have been obvious under 35 U.S.C. § 103: (1) the scope and content of the prior art; (2) the differences between the prior art and the claims at issue; (3) the level of ordinary skill in the pertinent art; and (4) secondary considerations such as commercial success, long-felt need, and failure of others. These four factors have governed every obviousness determination for nearly sixty years. According to Graham, the next step after considering those factors is to make the final determination. Is the invention obvious or not. But after working through the factors, a conscientious examiner or judge will often find that the hardest part of the analysis remains undone. The factors tell you what evidence to gather. They do not tell you how to get from that evidence to the legal conclusion.

That gap is not a product of changing times or increasing technological complexity. It was apparent from the beginning. Graham itself involved the combination of a host of prior art. The lower courts found that the prior art “as a whole in one form or another contains all of the mechanical elements” of the patent at issue. The Court could identify what the art contained, how the claims differed, and what a skilled plow mechanic would have known. Yet the four factors alone did not resolve the question. The Court still had to make an inferential leap: given all of this, would a person of ordinary skill have found the claimed rearrangement of shank and hinge plate obvious? Graham supplied no structured method for making that leap.

Over the following decades, the PTO and courts developed a set of structured analytical inquiries that serve as a second layer of doctrine, connecting Graham‘s evidentiary foundation to the ultimate legal conclusion. These doctrines are now so central to practice that it is easy to forget they appear nowhere in Section 103 and nowhere in Graham. They are: motivation to combine (would a person of ordinary skill have had a reason to put these references together?); reasonable expectation of success (would such a person have believed the combination would work?); teaching away (does the prior art point in the opposite direction?); and obvious to try (was the claimed solution among a finite set of predictable options a skilled artisan would have pursued?). Understanding where each of these fits within the Graham architecture is essential to understanding how obviousness actually works. I see these as bridges connecting the fundamental evidence to the conclusion of obviousness. They create a scaffold of reasoning that offers a pathway to what is otherwise an analytic leap.

What makes these bridging doctrines work is that they draw on all four Graham factors simultaneously, synthesizing the evidence into a structured inquiry that Graham itself does not provide. None of these sub-doctrines belongs exclusively to any single factor. Each pulls from wherever the relevant evidence lies, whether that is the prior art itself, the gap between the art and the claims, the skill level of the ordinary artisan, or the real-world evidence captured by secondary considerations. The discussion below examines each bridging doctrine and its role in connecting Graham‘s evidentiary inputs to the ultimate legal conclusion.

The PHOSITA: The "person having ordinary skill in the art" (PHOSITA) is a legal fiction central to patent law. This hypothetical person is presumed to know everything in the relevant prior art, to have ordinary creativity (but not inventive genius), and to work within the knowledge and capabilities typical of practitioners in the field. The PHOSITA standard appears in 35 U.S.C. § 103 and governs the obviousness inquiry. In KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), the Supreme Court emphasized that the PHOSITA is "a person of ordinary creativity, not an automaton," capable of drawing inferences and applying common sense beyond what is explicitly stated in the prior art.

Motivation to Combine

The motivation-to-combine inquiry asks whether a person of ordinary skill would have had a reason to combine the teachings of the cited prior art references. The doctrine’s origin traces to Application of Bergel, 292 F.2d 955 (CCPA 1961), where the Court of Customs and Patent Appeals held that the mere possibility of combining two disclosures does not render the combination obvious “unless the art also contains something to suggest the desirability of the proposed combination.” When the Supreme Court addressed motivation to combine in KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398 (2007), it acknowledged that Bergel “captured a helpful insight.” The Court did not eliminate the requirement but rejected the Federal Circuit’s “rigid and mandatory” application of what had become known as the teaching-suggestion-motivation (TSM) test. See Dennis Crouch, Today’s Obviousness Key: Motivation to Combine, Patently-O (Mar. 28, 2024).

The motivation inquiry bridges Graham‘s evidence by asking a synthetic question that no single factor answers on its own: given what the art discloses, what problems the field faces, what the ordinary artisan knows, and what the marketplace demands, would there have been a reason to make the claimed combination? The prior art (Factor 1) supplies much of the raw material: explicit suggestions in references, common approaches in the field, and problems identified in the literature. The level of ordinary skill (Factor 3) determines how the artisan would process that information, what inferences she would draw, and whether common sense or routine design practice would point toward the combination. But motivation can also emerge from secondary considerations (Factor 4).  KSR made this broad evidentiary base explicit: any “need or problem known in the field of endeavor at the time of invention and addressed by the patent can provide a reason for combining the elements in the manner claimed.”

The Federal Circuit’s decision in In re Kahn, 441 F.3d 977 (Fed. Cir. 2006), offered one of the more explicit judicial statements about where motivation fits within Graham, grounding it in “both the ‘scope and content of the prior art’ and ‘level of ordinary skill in the pertinent art’ aspects of the Graham test.” DyStar Textilfarben GmbH & Co. Deutschland KG v. C.H. Patrick Co., 464 F.3d 1356 (Fed. Cir. 2006), reinforced this, noting that motivation to combine is “also inextricably linked to the level of ordinary skill.” But neither Kahn nor DyStar acknowledged the role of secondary considerations as an independent source of motivation, even though the logic of KSR‘s market-pressure rationale plainly reaches Factor 4 evidence. What KSR changed was not the existence of the motivation requirement but the range of evidence that can satisfy it. Before KSR, the Federal Circuit had often demanded a specific teaching, suggestion, or motivation found in the references themselves. After KSR, the inquiry became more flexible, with motivation permissibly drawn from the full body of evidence that Graham assembles. But the Kahn requirement that there be “articulated reasoning with some rational underpinning” survived intact. The Federal Circuit continues to reverse the PTAB for failures of articulation.

The TSM Test Before and After KSR

Before KSR, the Federal Circuit required evidence of a "teaching, suggestion, or motivation" (TSM) to combine prior art references, and often demanded that this evidence be found in the references themselves or in the knowledge of a person of ordinary skill. Critics argued the test was applied too rigidly, making it difficult to invalidate patents on combinations of known elements. In KSR, the Supreme Court held that the TSM test was not wrong in principle but could not be applied as a "rigid and mandatory formula." Courts must consider the full range of reasons a skilled artisan might combine references, including common sense, market demand, and design incentives.

Reasonable Expectation of Success

If motivation to combine asks why a skilled artisan would put two references together, reasonable expectation of success asks whether that artisan would have reasonably believed the combination would work. The Federal Circuit has called the two inquiries “related but distinct.” Eli Lilly & Co. v. Teva Pharms. Int’l GmbH, 8 F.4th 1331 (Fed. Cir. 2021). The distinction is that a strong motivation to try a particular combination may coexist with genuine uncertainty about whether it will succeed, and in such cases, the absence of a reasonable expectation of success defeats obviousness even when motivation is present. Whether these two inquiries are truly independent in practice is debatable. In predictable technologies, motivation and expectation tend to rise and fall together: if a mechanical engineer has a reason to combine two components, she almost invariably expects the combination to work. It is principally in the unpredictable arts, as discussed below, that the two inquiries diverge in any meaningful way. But the case law treats them as separately required elements, and a party asserting obviousness must establish both.

This inquiry bridges Graham‘s evidence to the legal conclusion by asking whether the gap between the known art and the claimed invention is one that the PHOSITA could cross with a rational basis for believing the result would follow. The analysis draws on all of the Graham inputs. The differences between the prior art and the claims (Factor 2) define the size of the gap. The scope of the prior art (Factor 1) establishes what was known about how the relevant technology behaves. The level of ordinary skill (Factor 3) determines whether the artisan would view the gap as bridgeable or daunting. And secondary considerations (Factor 4) can cut in both directions: evidence of failure of others, for instance, may demonstrate that skilled artisans tried and failed to achieve what the patent claims, undermining any finding that a reasonable expectation of success existed. The standard is calibrated: “only a reasonable expectation of success, not absolute predictability, is necessary.” In re Longi, 759 F.2d 887, 897 (Fed. Cir. 1985). But “mere hope or desire” is not enough; there must be a factual basis for expecting the combination to succeed.

This is where the technology-specific calibration happens. In mechanical and electrical arts, where the behavior of components is generally predictable, the expectation of success often follows almost automatically once motivation is established. If a skilled engineer has reason to attach component A to component B, she usually has reason to believe it will work. But in pharmaceutical and biotechnology cases, the unpredictability of biological systems drives a wedge between motivation and expectation. A medicinal chemist may have ample reason to try combining two known compounds, but the unpredictability of drug-drug interactions, pharmacokinetics, or receptor binding may leave the outcome genuinely uncertain.  The result here is that the same doctrinal framework produces different outcomes across technological domains because the factual predicates for expectation of success differ.

Teaching Away

Teaching away is often presented as a separate bridging doctrine, but it is better understood as a feeder into the motivation-to-combine or expectation of success inquiries. If the prior art criticizes, discredits, or discourages the claimed combination, that is a reason the PHOSITA would not have been motivated to make it. A reference “teaches away” when it “criticize[s], discredit[s], or otherwise discourage[s]” the claimed combination. In re Fulton, 391 F.3d 1195, 1201 (Fed. Cir. 2004). The decisionmaker must weigh the evidence that would have pushed the artisan toward the combination against the evidence that would have pushed her away from it.

Like motivation, teaching away draws on multiple Graham inputs. Its most obvious source is the prior art itself (Factor 1): explicit statements in references that a combination would not work, or that a particular approach is disfavored or dangerous. But teaching away can also emerge from secondary considerations (Factor 4). Evidence that others in the field tried the approach and failed, or that industry practice moved in a different direction despite awareness of the components, can establish that the art as a whole pointed away from the combination. The level of ordinary skill (Factor 3) matters too: whether a particular cautionary statement in the prior art would actually dissuade a practitioner depends on how a person of that skill level would interpret it.

The doctrine has a hard edge and a soft edge. The hard edge is formal teaching away: an explicit statement in the prior art that the combination would not work, or would produce undesirable results. This is relatively straightforward to identify and, when present, is powerful evidence against obviousness. The soft edge is more interesting and more contested. In Laboratory Corp. of America Holdings v. Ravgen, Inc., No. 2023-1342 (Fed. Cir. Jan. 6, 2025), the Federal Circuit addressed evidence that fell short of formal teaching away but would nonetheless have “dissuaded” a person of ordinary skill from pursuing the combination. See Dennis Crouch, Not Quite Teaching Away: Federal Circuit Clarifies Evidence Needed to Defeat Motivation to Combine, Patently-O (Jan. 6, 2025). This intermediate category acknowledges that the prior art’s influence on the PHOSITA is not binary. A reference need not explicitly condemn a combination to reduce the likelihood that a skilled artisan would pursue it.

Obvious to Try: The Unifying Doctrine

The “obvious to try” doctrine, rehabilitated by KSR after decades of disfavor, provides the most explicit bridge between motivation and expectation of success, unifying both within a single analytical frame. The Federal Circuit has distilled KSR‘s guidance into a three-part test: (1) there must be a recognized problem or need in the field; (2) there must be a finite number of identified, predictable solutions; and (3) a person of ordinary skill must have been able to pursue the known options with a reasonable expectation of success. In re ICON Health & Fitness, Inc., 496 F.3d 1374 (Fed. Cir. 2007).

The structure of this test makes its bridging function transparent. Elements one and two establish motivation: the prior art and real-world conditions presented a known problem with identifiable solutions, as perceived by a person of ordinary skill. Element three demands a reasonable expectation of success: the gap between the known options and the claimed solution was one the PHOSITA could cross with confidence. And the limiting condition, the requirement that solutions be “finite” and “predictable,” prevents the doctrine from swallowing the nonobviousness requirement whole. Where the solution space is vast and outcomes uncertain, as the Federal Circuit held in In re Cyclobenzaprine Hydrochloride Extended-Release Capsule Patent Litigation, 676 F.3d 1063 (Fed. Cir. 2012), “obvious to try” does not apply, because the expectation-of-success prong cannot be satisfied.

The Scaffold and the Structure

None of these doctrines is a freestanding statutory requirement. None constitutes a “fifth Graham factor.” They are better understood as the analytical scaffold that patent law built to compensate for what Graham left unstructured: the inferential step from evidence to conclusion. What makes them effective is precisely that they cut across the Graham factors rather than being confined within any one of them. Motivation to combine synthesizes the prior art, the skill level of the artisan, and real-world market evidence into a single question about whether there was a reason to try, with teaching away feeding into that calculus as a counterweight. Reasonable expectation of success synthesizes the gap between art and claims, the state of knowledge in the field, and objective evidence of others’ failures into a single question about whether trying would have been rational. And obvious to try unifies both inquiries within a single doctrinal frame, demanding that the solution space be finite and the expectation of success reasonable. Each takes the evidence that Graham organizes and forges it into a structured inquiry that can actually resolve the ultimate question.

The Federal Circuit’s increasing willingness to police these doctrines as questions of law rather than fact, a pattern I have described as the “law/fact lever,” gives the appellate court substantial control over how the scaffold is constructed case by case. See Dennis Crouch, The Law/Fact Lever: How the Federal Circuit Can Control Obviousness Outcomes, Patently-O (Mar. 4, 2026). By recharacterizing a fact finder assessment of motivation or expectation of success as reflecting an error of “legal standard,” the court can review de novo what would otherwise receive deferential review. Whether this degree of appellate control is appropriate is a separate question, but the mechanism itself confirms the doctrinal status of these sub-inquiries: they are treated as legal architecture, not merely as factual assessments within the Graham framework.

The Supreme Court has shown little interest in further refining these doctrines. It denied certiorari in Vanda Pharmaceuticals Inc. v. Teva Pharmaceuticals USA, Inc. in 2024, declining to resolve whether “reasonable expectation of success” and KSR‘s “predictability” describe the same inquiry. Nearly two decades after KSR, the second layer of obviousness doctrine continues to develop at the Federal Circuit without direct Supreme Court supervision. For practitioners, the practical lesson is clear: winning and losing obviousness arguments depends less on the Graham factors themselves than on the scaffold built atop them. The factors organize the evidence. The bridging doctrines determine the outcome.

Most every patent applicant conducts at least a cursory prior art search before filing. Diligent applicants do a much more complete scouring of references. But there is a category of prior art that no search can uncover: applications that have been filed at the USPTO but not yet published. I have previously called these references “secret springing prior art” because they retroactively spring into existence as prior art only after eventually publishing. Dennis Crouch, Secret Springing Prior Art and Inter Partes Review, Patently-O (Oct. 4, 2024).

For this project I set out to measure just how much “dark matter” is out there. The answer depends on what you mean by “secret,” and the distinction turns out to matter quite a lot.

Two Kinds of Secret. The conventional measure of secret 102(a)(2) prior art asks a simple legal question: was the cited reference published before the applicant filed? If not, the applicant could not have known about it. By that measure, the problem looks large and growing. Nearly 30% of office action rejections now cite at least one legally secret reference, up from about 20% a decade ago.

But this legal definition overstates the practical problem. Many of the references cited as 102(a)(2) “secrets” are continuations or divisionals whose parent application was already published. Others are PCT national stage entries whose WIPO publication predated the citing application. In these cases, the specific document the examiner cited was technically unpublished at the critical date, but the same effective disclosure was publicly available in a family member. A diligent searcher could have found the substance of the reference at the time of filing, even if not the exact document.

To capture this distinction, I classified every 102(a)(2)/102(e) reference as practically secret (no family publication made the disclosure available before the applicant filed) or merely legally secret (the cited document was unpublished when applicant filed, but a parent or related publication may have already disclosed the same content). The results tell a substantially different story than the legal numbers alone.

This first chart uses examiner-cited references found on the front cover of issued patents.  The blue line shows the legal measure: the percentage of examiner-cited references that were unpublished at the time the applicant filed. The red dashed line shows the practical measure: references where no family member had published the disclosure either. The shaded gap between them represents references that were legally secret but practically discoverable.

Three things stand out. First is the dramatic decline from 2002 to 2015 and that appears in both measures.  That decline was a result of the American Inventors Protection Act (AIPA) 18-month publication requirement which genuinely reduced the secret prior art problem.  That publication began in 2001, and system required some amount of time before those publications became a central feature of patent examination.

Second, you can see the beginning of a rise in the rates of secret art citation over the past few years.  That increase, I believe is driven by a growing global filing volume (more applications in the 18-month unpublished pipeline at any given time) and the AIA’s Hilmer abolition (discussed below). A third driver worth mentioning is the shift toward faster-moving technology areas as a share of overall filings. Those fields have inherently higher secret PA rates because of denser filing in overlapping technology space.

Third is the widening gap between legally secret and practically secret.  This third trend is almost entirely explained by rising continuation and international filing rates. The typical patent now is part of a larger patent family – making it more likely that a prior filing has already been published. The gap is essentially a measure of continuation practice intensity interacting with universal pre-grant publication.

What Is Secret Prior Art?

Under 35 U.S.C. § 102(a)(2), a patent application's effective filing date can serve as its prior art date against later-filed applications, even though the reference was not published until months or years later. For example, if Applicant A files on January 1 and Applicant B files on March 1, A's application can be used against B once A eventually publishes (typically 18 months after filing). Applicant B had no way to discover A's application at the time of filing. Under pre-AIA law, this category of prior art was governed by § 102(e). The doctrine traces to the Supreme Court's 1926 decision in Alexander Milburn Co. v. Davis-Bournonville Co., 270 U.S. 390 (1926). I wrote more on that history back in 2025. Dennis Crouch, Thinking Back on Milburn and Secret/Springing Prior Art, Patently-O (July 15, 2025).

Methodology. My study here draws on two data sources. The front-page citation analysis covers 233 million citation records from 9 million granted US patents (2002-2026), using the grant year as the time axis. For office-action-level analysis, I used a random sample of approximately 10,000 office actions per year from the USPTO Patent Examination Data System API, covering 2008 through early 2026. This includes both non-final and final rejections across all technology areas and includes applications that were ultimately granted and abandoned as well as some still pending.

For each reference cited in a rejection, I computed “regime-aware” prior art dates. Under post-AIA law (applications with effective filing dates on or after March 16, 2013), the reference’s 102(a)(2) prior art date is its earliest worldwide filing date, including foreign priority claims. Under pre-AIA law, the reference’s prior art date is its earliest effective U.S. filing date only, following the Hilmer doctrine, see In re Hilmer, 359 F.2d 859 (C.C.P.A. 1966), as modified to also reach back to English-published PCT applications filed on or after November 29, 2000. I then checked whether any parent application (continuation or divisional) or WIPO PCT publication had made the same disclosure publicly available before the citing application’s filing date. For this study, I ignored the other requirements for 102(a)(2)/102(e) qualification, such as “another inventor.”

The AIPA Story (2002-2015). Before the American Inventors Protection Act of 1999 took effect on November 29, 2000, most pending patent applications remained entirely secret until they issued as patents, which could take years. AIPA introduced mandatory 18-month publication for most applications, dramatically compressing the window during which a pending application could serve as secret prior art.

But AIPA’s effect was not instantaneous. Applications filed before November 2000 that were still in prosecution or recently granted continued to appear as examiner-cited references well into the late 2000s. The data captures AIPA’s gradual impact: the legal secret rate fell from 25% in 2006 to 12% by 2016. By 2015, virtually the entire relevant prior art pool consisted of applications subject to 18-month publication, and both measures bottomed out.

The Hilmer Doctrine and Its Demise

Under pre-AIA law, a foreign-origin patent application's prior art date was limited to its U.S. filing date, not its earlier foreign priority date. This was known as the Hilmer doctrine, after In re Hilmer, 359 F.2d 859 (C.C.P.A. 1966). The America Invents Act abolished this limitation. Under post-AIA § 102(a)(2) and § 102(d), a reference's prior art date now reaches back to its earliest worldwide filing date, including foreign priority claims. This change expanded the pool of secret prior art by giving foreign-origin references an earlier effective date. 

The chart above uses office action rejection data — references used by examiners to reject claims. It shows a similar trend to that seen in just the general citation data.  I looked here at the percent of office actions that relied upon at least one secret reference. The idea here is that …

An additional approach I took was a counterfactual analysis, comparing actual secret prior art rates against what the rate would have been under pre-AIA Hilmer rules, estimates that the AIA’s broader definition accounts for 3.2 additional percentage points of legally secret prior art by 2025. But approximately a third of that expansion  is not truly secret prior art because those cases had been already published in a different form. When measured by practical secrecy, the AIA’s net contribution drops  is about 2.2 percent because many of the foreign-priority references newly captured by the AIA 102(a)(2) had related publications, including PCT applications published by WIPO or continuation families with earlier PGPubs, that made their disclosures available to searchers.

Technology Variation. Secret prior art is not evenly distributed across technologies. Electrical engineering and telecommunications have the highest rates. Slower moving mechanical engineering has the lowest.

What Secret Prior Art Looks Like. About 79% of secret prior art references are published applications (pre-grant publications) with an average secrecy gap of 371 days. The remaining 21% are patents that were not published as applications before grant, with a slightly longer average secrecy gap.

Not What I Expected. When I started this project, my prior assumption was that the accelerating pace of technology development would be compressing prior art into shorter timelines, that examiners would increasingly be citing newer, more recent references as innovation cycles shortened. That intuition turns out to be almost exactly wrong. Mean examiner-cited reference age has grown during this 18-year period from about 4 years to over 6 years. Examiners are reaching further back in time, not less. Even in the fastest-moving fields such as EE and computing, reference ages climbed. Part of the explanation is that the growing cumulative stock of published prior art gives examiners a deeper well to draw from, and improved search tools make it easier to find older references. Technology may be moving faster, but the prior art landscape is getting deeper.

The Lynk Labs Connection. The distinction between legal and practical secrecy matters for the ongoing legal debate, but it does not resolve it. In Lynk Labs, Inc. v. Samsung Electronics Co., 125 F.4th 1120 (Fed. Cir. 2025), the Federal Circuit held that a published patent application could be used as prior art in an inter partes review proceeding even though it was not publicly accessible until after the challenged patent’s filing date. The court concluded that the term “printed publication” in 35 U.S.C. § 311(b) is “temporally agnostic.” Dennis Crouch, Publications Before Publishing and the Federal Circuit’s Temporal Gymnastics, Patently-O (Jan. 14, 2025). The Supreme Court denied certiorari on March 9, 2026, leaving the Federal Circuit’s approach intact.

In urging denial, the Solicitor General argued that the question presented had “limited practical importance” because so few cases fall within the secret prior art window. The data presented here rebuts that framing with about 25% of office action rejections relying on prior art that was not available at the time of filing.

The question is not going away. The same § 311(b) issue is squarely presented in the pending Federal Circuit appeal in VLSI Technology LLC v. Patent Quality Assurance LLC, Nos. 2023-2298, -2354 (Fed. Cir.). And the practical consequences remain real: an applicant whose rejection rests on a practically secret reference had no opportunity to design around it, distinguish it during prosecution planning, or even know it existed.

The broader policy question also benefits from this more granular view. The European Patent Office permits secret prior art to be used only for novelty, not for obviousness, confining the inventive step analysis to what a person of ordinary skill actually knew at the relevant date.  In the US most uses of 102(a)(2) art is for obviousness rejections. Adopting the European approach would thus eliminate not just a marginal category of rejections, but the primary use of secret prior art in U.S. patent examination.