Prior Art Under the America Invents Act: Section 102, the On-Sale Bar, Public Use, and the One-Year Grace Period

A founder emails her patent lawyer on a Friday afternoon. The pitch deck went out to forty investors last spring, the prototype was on a folding table at a trade show in Las Vegas fourteen months ago, two beta customers have been paying a "pilot fee" since January, and a competitor just launched something that looks suspiciously similar. She wants to file on Monday. The lawyer's first question is not "what did you invent?" It is "what did you already tell the world, when, and under what terms?" The answer decides whether there is anything left to patent.

That question, in every one of its forms, is the subject of this article. Prior art is the body of public knowledge against which a patent claim is measured for novelty under 35 U.S.C. § 102 and for nonobviousness under 35 U.S.C. § 103. What counts as prior art, when it counts, and who can rely on it are statutory questions with a great deal of case law layered on top. The America Invents Act (AIA) rewrote the statute in 2011, and because the old statute still governs patents with claims that predate March 16, 2013, a working lawyer has to carry two versions of § 102 in their head at once.

The short answer

Under the AIA, a claimed invention is unpatentable if, before its effective filing date, it was patented, described in a printed publication, in public use, on sale, or otherwise available to the public anywhere in the world (§ 102(a)(1)), or if it was described in a U.S. patent, published U.S. application, or published PCT application that names a different inventor and was effectively filed earlier (§ 102(a)(2)). The statute carves out a one-year grace period for the inventor's own disclosures and disclosures derived from the inventor (§ 102(b)(1)), and it excludes from § 102(a)(2) earlier applications that were derived from the inventor, that postdate the inventor's own public disclosure, or that are commonly owned (§ 102(b)(2)).

Three practical rules follow. First, the grace period is a safety net for accidents, not a plan: it does nothing abroad, it protects only the inventor's own disclosures, and the courts read its second prong narrowly. Second, a sale counts even if it is secret, because Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA, Inc., 586 U.S. 123 (2019), held that the AIA did not change the settled meaning of "on sale." Third, a reference is prior art only if the person relying on it can prove its date and its public accessibility, and in district court must do so by clear and convincing evidence under Microsoft Corp. v. i4i Ltd. Partnership, 564 U.S. 91 (2011). Everything else in this article is elaboration on those three rules.

For the vocabulary this article assumes (claims, specification, effective filing date, person of ordinary skill), see Patent Basics: A Plain-English Guide and How to Read a Patent: Claims, Specification, and Prosecution History. For the procedural companion to this article, see Finding, Qualifying, and Using Prior Art: A Practical Guide.

Which version of section 102 applies

The AIA's first-inventor-to-file provisions apply to any application, and any patent issuing from it, that contains or ever contained a claim with an effective filing date on or after March 16, 2013. Everything else is governed by pre-AIA § 102. The effective filing date of a claim is defined in 35 U.S.C. § 100(i) as the actual filing date or, if the claim is entitled to the benefit of an earlier application under 35 U.S.C. § 119 or 35 U.S.C. § 120, the filing date of the earliest application that actually supports the claim under 35 U.S.C. § 112.

Two consequences are easy to miss. The regime (AIA or pre-AIA) is chosen application by application, but effective filing dates are determined claim by claim. An application filed in 2014 claiming priority to a 2012 provisional is a pre-AIA application if every claim is fully supported by the provisional, and an AIA application if even one claim is not. Once an application has ever contained a post-March 16, 2013 claim, it stays an AIA application even if that claim is later cancelled. The transitional rule is in section 3(n) of the AIA (Pub. L. 112-29), and the USPTO's treatment is at MPEP § 2159. Transition applications (AIA applications that also contain, or once contained, a claim entitled to a pre-March 16, 2013 date) carry an extra burden under section 3(n)(2): pre-AIA § 102(g) applies to them as well, which is the kind of problem that keeps claim-by-claim priority analysis in business.

The practical rule for a litigator: read the face of the patent and the priority chain before doing anything else. The regime determines whether a foreign public use counts (AIA yes, pre-AIA no), whether the patentee can swear behind a reference by proving an earlier invention date (pre-AIA yes, AIA no), and whether a secret third-party sale is prior art (generally no under either, with wrinkles discussed below). A prior art search run under the wrong regime is a wasted search.

The AIA categories at a glance

Each category also feeds § 103. A reference that does not anticipate because it lacks one element can still be combined with other art to render the claim obvious; the obviousness analysis is covered in Overcoming Obviousness Rejections: A Comprehensive Guide to Section 103 Analysis. What this article covers is the threshold question: is this thing prior art at all?

Printed publications and the public accessibility test

"Printed publication" is a term of art that has almost nothing to do with printing. The touchstone is public accessibility: a reference qualifies if it was disseminated or otherwise made available to the extent that a person interested in the subject matter, exercising reasonable diligence, could locate it. The Court of Customs and Patent Appeals set that standard in In re Wyer, 655 F.2d 221 (CCPA 1981), for a microfilmed Australian patent application, and the Federal Circuit has applied it ever since. The USPTO's summary of the doctrine is at MPEP §§ 2128 and 2128.01, and Chisum on Patents ch. 3 collects the older cases.

The leading cases map the boundaries:

• A single thesis in a single library can be enough. In re Hall, 781 F.2d 897 (Fed. Cir. 1986), held that a doctoral dissertation indexed and shelved in the library of the University of Freiburg was a printed publication, because a researcher in the field could have found it through the library's catalog. One copy, one library, properly indexed: prior art.
• Three theses that were not meaningfully indexed were not enough. In re Cronyn, 890 F.2d 1158 (Fed. Cir. 1989), reached the opposite result where undergraduate theses were listed only on index cards filed by the student's name in a departmental shoebox. The reference was physically present but not accessible to anyone searching by subject.
• A poster displayed for a few days with no copies distributed can be a publication. In re Klopfenstein, 380 F.3d 1345 (Fed. Cir. 2004), involved a fourteen-slide poster shown for two and a half days at a scientific conference and again for less than a day at a university. No copies were handed out. The court held it was a printed publication anyway, applying four factors: the length of time the display was exhibited, the expertise of the target audience, the existence or absence of reasonable expectations that the material would not be copied, and the simplicity or ease with which the material could have been copied. Those Klopfenstein factors are now the standard framework for transient displays and presentations.
• Online material counts if an interested person could have found it. Blue Calypso, LLC v. Groupon, Inc., 815 F.3d 1331 (Fed. Cir. 2016), affirmed a finding that a paper posted on an individual researcher's personal web page was not shown to be publicly accessible, because there was no evidence that the page was indexed by search engines or that a skilled artisan would have known to look there. The contrast with Voter Verified, Inc. v. Premier Election Solutions, Inc., 698 F.3d 1374 (Fed. Cir. 2012), where an article in an online forum well known to people interested in voting-system security was held accessible, shows that the question is not "was it online" but "could the interested public have found it."
• Materials posted on a government website with public notice are accessible. Jazz Pharmaceuticals, Inc. v. Amneal Pharmaceuticals, LLC, 895 F.3d 1347 (Fed. Cir. 2018), held that FDA advisory committee materials (a briefing package, slides, and meeting minutes and transcript) posted on the FDA's website and announced in the Federal Register were printed publications. The court emphasized that the Federal Register notice directed interested persons to the exact location of the materials and that the materials were available for months before the critical date. No evidence that anyone actually downloaded them was required.
• Distribution to a limited group, without restriction, can be enough; distribution with an expectation of confidentiality is not. Samsung Electronics Co. v. Infobridge Pte. Ltd., 929 F.3d 1363 (Fed. Cir. 2019), vacated a Board finding that a draft video-coding standard emailed to a standards group's listserv was not publicly accessible. The Board had faulted the challenger for failing to prove the draft was "generally" or "widely" disseminated; the court held that a limited distribution to interested members of the art can suffice and that nobody has to prove a particular person actually opened the document, and it remanded for findings on who received the email and whether it carried an expectation of confidentiality. Acceleration Bay, LLC v. Activision Blizzard Inc., 908 F.3d 765 (Fed. Cir. 2018), went the other way for a technical report uploaded to a university's online repository: the repository's search function was so crude (searchable only by author name and year, not subject) that a diligent researcher could not have found it. And Medtronic, Inc. v. Barry, 891 F.3d 1368 (Fed. Cir. 2018), remanded for a finding on whether a video and slides shown to surgeons at industry meetings were accessible, listing the size and nature of the meetings, whether attendees were expected to keep the materials confidential, and whether the audience was the relevant skilled public as the controlling facts.
• Product manuals can be printed publications when they are actually made available to customers. The Federal Circuit in Weber, Inc. v. Provisur Technologies, Inc., 92 F.4th 1059 (Fed. Cir. 2024), reversed a Board finding that operating manuals for commercial food slicers were not printed publications. The Board had stressed that the manuals went to only about ten customers and carried a copyright notice forbidding reproduction. The court held that the manuals' purpose was to explain the machines to the people who bought and serviced them, that owners were told to pass the manuals along when they resold a slicer, and that a boilerplate copyright notice is not a confidentiality obligation. The decision is a warning for every manufacturer whose manuals describe how its own products work: those manuals are prior art against the manufacturer's later patents on the same products, and they are prior art against everyone else too.

The evidentiary wrinkle is that the challenger must prove not just the content of a reference but the date it became accessible. For a journal article the date is usually easy. For a web page it is not. Valve Corp. v. Ironburg Inventions Ltd., 8 F.4th 1364 (Fed. Cir. 2021), reversed a Board ruling that an online article about a game controller was not shown to be prior art. The petitioner's exhibit could be authenticated under Rule 901(b)(3) by comparing it with copies of the same article that sat in the certified prosecution histories of the patent owner's own related patents (copies an examiner had pulled from the Wayback Machine), and the fact that an examiner could retrieve the article before the critical date showed that the public could too. The broader rule is that archive printouts are authenticated under Fed. R. Evid. 901 by an affidavit from the Internet Archive's records custodian, by testimony of someone who viewed the page on the relevant date, or by circumstantial evidence such as the archive's own date stamps and the page's internal consistency. Our separate treatment of that problem, Capturing the Web: A Practitioner's Guide to Authenticating Website Screenshots as Evidence in Federal Court, goes into the mechanics.

What "patented" adds

The "patented" category in § 102(a)(1) is narrower than it looks. A foreign patent is generally prior art under this prong as of the date its rights became enforceable and its contents became available to the public, and a patent that is granted but kept secret (some jurisdictions have such regimes for defense-related inventions) generally is not prior art under the "patented" prong at all, because the public could not learn from it. MPEP § 2126 collects the rules. In practice almost every patent that qualifies as "patented" also qualifies as a printed publication once it is published, and the printed publication analysis controls.

Public use

A public use is any use of the claimed invention by a person other than the inventor who is under no limitation, restriction, or obligation of secrecy, or any use by the inventor that is accessible to the public. The grandfather of the doctrine is Egbert v. Lippmann, 104 U.S. 333 (1881), in which an inventor gave his corset-steel invention to a woman who wore it, invisibly, under her clothes for years before he filed. The Supreme Court held that the use was public: the number of users was irrelevant, the fact that the device was hidden was irrelevant, and what mattered was that the inventor had given the invention to another person for ordinary use with no restriction on its use or disclosure. A use by one person, in private, under no obligation of secrecy, is a public use. Two years later, Hall v. Macneale, 107 U.S. 90 (1883), applied the same logic to safes whose patented internal bolts could not be seen once the safes were sold and installed: the safes were in public use, hidden features and all.

The modern formulation asks whether the invention was "accessible to the public" or "commercially exploited." Invitrogen Corp. v. Biocrest Manufacturing, L.P., 424 F.3d 1374 (Fed. Cir. 2005), held that the patentee's own secret, in-house use of a claimed process to make cells for internal research was not a public use, because the use was neither accessible to the public nor a commercial exploitation; using the invention internally is not the same as selling it or giving it to others. Dey, L.P. v. Sunovion Pharmaceuticals, Inc., 715 F.3d 1351 (Fed. Cir. 2013), applied the same test to a third party's clinical trial and reversed a summary judgment of invalidity. Trial participants took the drug home for twelve weeks and were not forbidden to talk about the study, but they were never told the formulation, they signed consent forms limiting the medication to their own use and requiring them to return unused doses, and the investigators signed formal confidentiality agreements; a fact-finder could conclude the study ran with a reasonable expectation of confidentiality as to what was being tested. Third-party uses cut both ways: a third party's use that is open and unrestricted is a public use that can invalidate someone else's patent, as in Baxter International, Inc. v. COBE Laboratories, Inc., 88 F.3d 1054 (Fed. Cir. 1996), where a government researcher used a centrifuge in front of coworkers who owed no duty of confidentiality, while a third party's secret commercial use is not, under W.L. Gore & Associates, Inc. v. Garlock, Inc., 721 F.2d 1540 (Fed. Cir. 1983). Those cases together establish that the "public" in public use means freely available use, not merely use outside the inventor's lab.

The AIA kept the words "in public use," and nothing in its text or in Helsinn suggests the courts will give them a new meaning, so the pre-AIA cases remain the working law. The modern template for the trade show problem is Minerva Surgical, Inc. v. Hologic, Inc., 59 F.4th 1371 (Fed. Cir. 2023), decided under pre-AIA § 102(b). Minerva brought fifteen working prototypes of its endometrial ablation device to the field's biggest annual meeting (the inventor called it the industry's Super Bowl) almost two years before its priority date, and showed them at its booth, in meetings with physicians and other attendees, and in a technical presentation, without asking anyone to sign anything. The court held that was a public use. The standard does not depend on whether attendees physically handled the device; the devices on display embodied the claim; and the invention was ready for patenting because Minerva had working prototypes, tested on extirpated tissue, and enabling technical documents. Contrast Motionless Keyboard Co. v. Microsoft Corp., 486 F.3d 1376 (Fed. Cir. 2007), where an inventor showed a prototype keyboard to potential investors (most under nondisclosure agreements), a friend, and a business partner without ever connecting it to a computer. Those were visual displays, not uses, and a single typing test performed under a nondisclosure agreement did not rise to a public use either. The line between the two cases is the line every founder should memorize: showing a working product to the trade, without restriction, is a use; letting a few people look at it, under confidentiality, is not.

The experimental use negation

Experimental use is not an exception to the bar; it is a reason the use was never "public" in the statutory sense. The doctrine comes from City of Elizabeth v. American Nicholson Pavement Co., 97 U.S. 126 (1877), in which the inventor laid a section of wooden pavement on a public toll road in Boston and watched it for six years to see whether it would hold up. The Supreme Court held that a bona fide test of the invention, conducted under the inventor's control and for the purpose of perfecting it, was not a public use even though the public drove over it every day. The use was in public; it was not a public use.

The Federal Circuit has turned that principle into a factor list. In Clock Spring, L.P. v. Wrapmaster, Inc., 560 F.3d 1317 (Fed. Cir. 2009), the inventors had demonstrated their pipeline-repair method on a working gas line almost three years before filing, in front of representatives of other pipeline companies who owed no duty of confidentiality. The patentee argued the demonstration was a durability test. The court disagreed: nothing in the contemporaneous reports said the demonstration was designed to test the claimed method for purposes of a patent application; its stated purpose was to show the industry that minimally trained crews could install the product, and testing aimed at winning acceptance from regulators and customers is not experimentation in the patent sense. The court applied the considerations that matter, which the Federal Circuit has catalogued as: the necessity for public testing, the amount of control the inventor retained, the nature of the invention, the length of the test period, whether payment was made, whether there was a secrecy obligation, whether records were kept, who conducted the experiment, the degree of commercial exploitation, whether the invention reasonably required evaluation under actual conditions of use, whether testing was systematic, whether the inventor continually monitored the invention, and the nature of contacts with potential customers. The list comes from Allen Engineering Corp. v. Bartell Industries, Inc., 299 F.3d 1336 (Fed. Cir. 2002), an on-sale case, and Clock Spring confirmed that it applies equally to public use. Two further limits apply. First, the experimentation must be directed at the claimed features or features inherent in them, Electromotive Division of General Motors Corp. v. Transportation Systems Division of General Electric Co., 417 F.3d 1203 (Fed. Cir. 2005), so testing whether customers like a product does not count; in In re Smith, 714 F.2d 1127 (Fed. Cir. 1983), in-home consumer testing of a carpet product was market research, not experimentation. Second, experimental use cannot negate a public use once the invention has been reduced to practice, a rule Clock Spring drew from In re Omeprazole Patent Litigation, 536 F.3d 1361 (Fed. Cir. 2008). The same testing evidence also bears on whether the invention was "ready for patenting" at all. Barry v. Medtronic, Inc., 914 F.3d 1310 (Fed. Cir. 2019), upheld a jury verdict that a surgeon's use of his spinal technique in three operations before the critical date did not bar his patent, because the jury could find that post-operative follow-up was needed to know whether the method worked, so the invention was not yet ready for patenting and the uses were experimental. In practice the question is often where in the analysis the evidence lands rather than whether it counts.

For the inventor who wants to rely on experimental use, the lesson is documentary: write down that the test is a test, retain control of the prototype, keep testing records, have the users sign something, and do not take money. For the challenger, the lesson is the mirror image: the absence of each of those things is evidence that the use was commercial.

The on-sale bar

An invention is "on sale" when two things are true: it is the subject of a commercial offer for sale, and it is ready for patenting. That is the test of Pfaff v. Wells Electronics, Inc., 525 U.S. 55 (1998), which rejected an earlier "totality of the circumstances" approach and the argument that the invention had to be reduced to practice before a sale could count. In Pfaff, the inventor accepted a purchase order for 30,100 computer chip sockets based on detailed engineering drawings before any socket had been built. The Court held the invention was ready for patenting because the drawings were sufficient to enable a skilled person to make it, and the order was a commercial sale. The patent was invalid. The principle behind the bar is older than the statutory words: Pennock v. Dialogue, 27 U.S. 1 (1829), held that inventors who allowed their fire hose to be made and sold for years before applying had lost the right to a patent, because an inventor may not exploit an invention commercially and then claim a monopoly whose term starts only when he finally applies.

Commercial offer for sale. The Federal Circuit measures this by the general law of contracts: an offer that the other side could accept to form a binding contract, judged by the standards of the Uniform Commercial Code and the Restatement (Second) of Contracts. See Group One, Ltd. v. Hallmark Cards, Inc., 254 F.3d 1041 (Fed. Cir. 2001). Price quotations, advertising, and marketing that do not rise to an acceptable offer are not enough, though they can be evidence of the surrounding commercial activity. A single offer is enough; no sale need be completed; the offeree need not accept; and the offeror need not be the inventor. A license of rights to practice a process is not, by itself, a sale of the process, In re Kollar, 286 F.3d 1326 (Fed. Cir. 2002), but an offer to perform a claimed method for a customer is an offer of the method, Scaltech Inc. v. Retec/Tetra, LLC, 269 F.3d 1321 (Fed. Cir. 2001).

Ready for patenting. Either an actual reduction to practice (a working embodiment that performs its intended function) or drawings or descriptions sufficiently specific to enable a skilled person to practice the invention. The second prong means an invention can be "ready" before it exists.

Secret sales count. The AIA's addition of the phrase "or otherwise available to the public" prompted an argument that "on sale" now required a sale that itself disclosed the invention to the public. In Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA, Inc., 586 U.S. 123 (2019), the Supreme Court unanimously rejected that reading. Helsinn had entered a supply and purchase agreement with a distributor for its palonosetron formulation, announced the existence of the agreement in a press release and an SEC filing, but kept the dosage details confidential. The Court held that "on sale" was a term with a settled pre-AIA meaning that included sales that did not disclose the invention's details, and that Congress's reenactment of the phrase carried that meaning forward. The catch-all did not narrow it. The practical rule: a confidential supply agreement, a signed purchase order under NDA, or a private license-plus-sale of product is prior art against the seller's later patent if it predates the effective filing date and is not saved by the grace period.

What is not a sale. The en banc Federal Circuit in The Medicines Co. v. Hospira, Inc., 827 F.3d 1363 (Fed. Cir. 2016) (en banc), held that a patentee's contract with a contract manufacturer to make batches of its drug for the patentee's own use was not a commercial sale of the invention. The manufacturer sold manufacturing services; title to the product never passed to anyone but the patentee; the transaction did not put the invention in the commercial marketplace. The court identified the touchstone as whether the transaction bears the general hallmarks of a sale under Uniform Commercial Code § 2-106, treated the absence of title transfer and the confidentiality imposed on the manufacturer as significant (though not dispositive), and held that stockpiling inventory, without an actual sale or offer, is preparation for commerce rather than commerce. The decision gives companies that outsource production a defensible path, provided the contract is written as a services agreement, the supplier never takes title, and the supplier has no right to sell to anyone else. The court was careful to add limits: an inventor who charges others a fee to use a new machine can put it "on sale" without ever transferring title, and the long-standing rule that selling products made by a secret process bars a later patent on the process remained intact.

Later Federal Circuit refinements.

• Quest Integrity USA, LLC v. Cokebusters USA Inc., 924 F.3d 1220 (Fed. Cir. 2019), affirmed the invalidity of three claims because the patentee itself had sold furnace-tube inspection services to a refinery for about $72,000 before the critical date and delivered reports whose color-coded strip charts met the claimed display limitation. Performing a patented method for a paying customer, or offering to, puts the method on sale. (Two other claims went back for trial because the district court had wrongly disregarded inventor declarations as sham affidavits, a reminder that on-sale disputes are fact disputes.)
• Sunoco Partners Marketing & Terminals L.P. v. U.S. Venture, Inc., 32 F.4th 1161 (Fed. Cir. 2022), reversed a finding of experimental use where the inventors' company, two days before the critical date, had offered to sell and install an automated butane-blending system at a customer's terminal in exchange for the customer's commitment to buy at least 500,000 barrels of butane over roughly five years. The court held that the offer was commercial on its face, that language in the agreement about "testing" the equipment reflected customer acceptance testing rather than experimentation on the claimed invention, and that the inventor's stated subjective purpose could not override the objective terms of the deal. The case is the leading modern authority on why a commercial agreement with a "pilot" or "testing" label does not become experimental by labeling.
• Celanese International Corp. v. International Trade Commission, 111 F.4th 1338 (Fed. Cir. 2024), confirmed that the pre-AIA "forfeiture" rule of Metallizing Engineering Co. v. Kenyon Bearing & Auto Parts Co., 153 F.2d 516 (2d Cir. 1946), and its Federal Circuit application in D.L. Auld Co. v. Chroma Graphics Corp., 714 F.2d 1144 (Fed. Cir. 1983), survived the AIA. Celanese had used its secret process to make the sweetener acesulfame potassium and sold the product for years before filing on the process. The court held that selling a product made by a secret process places the process "on sale" under AIA § 102(a)(1), relying on Helsinn's reasoning that Congress reenacted the term with its settled meaning. An inventor who commercially exploits a process in secret for more than the grace period loses the right to patent the process.
• Sanho Corp. v. Kaijet Technology International Ltd., 108 F.4th 1376 (Fed. Cir. 2024), addressed the exceptions rather than the bar itself, and is discussed below: a private sale by the inventor, although it counts as an "on sale" disclosure, is not a "public" disclosure that knocks out a third party's intervening patent application under § 102(b)(2)(B).

Supplier and distributor relationships. The Federal Circuit has sometimes been asked whether a sale by a supplier to the patentee itself is "on sale." Special Devices, Inc. v. OEA, Inc., 270 F.3d 1353 (Fed. Cir. 2001), held that it can be: there is no "supplier exception" to the on-sale bar, and a supplier's sale of the claimed product to the patentee more than a year before filing invalidated the patent. Hamilton Beach Brands, Inc. v. Sunbeam Products, Inc., 726 F.3d 1370 (Fed. Cir. 2013), applied the same rule to a purchase order Hamilton Beach placed with its foreign manufacturer for a slow cooker. Medicines Co. read both cases narrowly: Special Devices stands only for the proposition that a transaction with all the hallmarks of a commercial sale is not exempt merely because the seller is a supplier (the inventor there had conceded the transaction was a commercial sale), and in Hamilton Beach the inventor never argued that buying from its own supplier was not a commercial sale. The line between the cases is where many modern on-sale disputes are fought, and it is drawn by the documents: who held title, what was being paid for, whether the supplier could sell to anyone else, and whether the goods were for the patentee's own stockpile or for the market.

The catch-all: "otherwise available to the public"

The AIA's catch-all has not generated much independent case law, which is itself the lesson. The USPTO reads it as covering any disclosure that makes the invention available to the public but that does not fit neatly into the other categories: an oral presentation at a conference, a demonstration at a trade show, a video posted online, a product displayed in a store window. MPEP § 2152.02(e). Most of those also qualify as a public use or a printed publication under the cases above, so the catch-all mostly operates as a backstop. Its main doctrinal significance has been negative: Helsinn held that it does not import a "public" requirement into the older categories.

Earlier-filed applications: section 102(a)(2) and section 102(d)

The second category of AIA prior art is the earlier-filed U.S. patent document. Under § 102(a)(2), a claimed invention is unpatentable if it was described in a U.S. patent, a published U.S. application, or a published PCT application designating the United States, that names another inventor and was "effectively filed" before the claimed invention's effective filing date. The reference becomes prior art as of its effective filing date, not its publication date, even though nobody could have read it until it published. That is the price of a first-to-file system: whoever filed first wins, and the earlier filer's disclosure counts against everyone who filed later.

Section 102(d) defines "effectively filed." A patent document is effectively filed, as to any subject matter it describes, on the earliest date for which it is entitled to claim priority or benefit under 35 U.S.C. § 119, § 120, or 35 U.S.C. § 365 to an earlier application that describes that subject matter. Two changes from pre-AIA law are buried in that sentence. First, a foreign priority date now counts: an AIA reference patent that claims priority to a Japanese application is prior art as of the Japanese filing date, provided the Japanese application describes the subject matter being relied on. That abolishes the Hilmer rule discussed below. Second, the reference's priority application need only describe the relied-on subject matter; it does not have to support the reference's claims.

That second point is where the pre-AIA and AIA regimes diverge sharply, and where litigators regularly trip. Under pre-AIA § 102(e), Dynamic Drinkware, LLC v. National Graphics, Inc., 800 F.3d 1375 (Fed. Cir. 2015), held that a reference patent is entitled to its provisional filing date as prior art only if the provisional supports at least one claim of the reference patent under § 112, and that the challenger bears the burden of proving it. Five years earlier, In re Giacomini, 612 F.3d 1380 (Fed. Cir. 2010), had held that a pre-AIA reference patent could be prior art as of its provisional filing date where the provisional disclosed the relied-on subject matter; Dynamic Drinkware added the claim-support requirement on top. The AIA text points the other way for AIA references: § 102(d)(2) asks only whether the earlier application "describes the subject matter," and the USPTO applies it that way (MPEP § 2154.01(b)). The practical effect is that an AIA reference patent reaches back to any earlier application in its chain, foreign or domestic, that describes the relevant disclosure. Because patent owners still raise the Dynamic Drinkware argument, a careful challenger maps the relied-on passages to the priority document and, as a fallback, shows that the priority document also supports at least one of the reference's claims.

Note what § 102(a)(2) does not cover. Foreign patents and foreign published applications that are not PCT applications designating the United States are not § 102(a)(2) references; they are prior art only as of the date they became publicly available, under § 102(a)(1). A confidential, unpublished U.S. application is never prior art under either subsection, because § 102(a)(2) requires that the reference have been published or issued, and 35 U.S.C. § 122 keeps unpublished applications secret.

The one-year grace period, and why relying on it is dangerous

Section 102(b)(1) removes from § 102(a)(1) any disclosure made one year or less before the effective filing date if (A) the disclosure was made by the inventor, a joint inventor, or someone who obtained the subject matter from the inventor, or (B) the subject matter disclosed had, before that disclosure, been publicly disclosed by the inventor or someone who obtained it from the inventor. Prong (A) is the inventor's own grace period. Prong (B) is the "first to publish" shield: once the inventor has publicly disclosed, a third party's independent disclosure of the same subject matter during the following year does not count against the inventor.

The grace period is real and it saves applicants every week. It is also narrower than most inventors believe, for four reasons.

It only runs one year, and the year is measured from the effective filing date. A provisional application filed within the year preserves the date only for what the provisional actually describes. If the nonprovisional adds subject matter, the added claims get the later date, and a disclosure thirteen months before the nonprovisional is outside the grace period as to them.

It does nothing abroad. Most of the world applies absolute novelty: any public disclosure before the priority date, by anyone including the inventor, destroys novelty. The European Patent Convention has only a six-month exception for evident abuse and certain international exhibitions. Japan, Korea, and a handful of other countries have limited grace periods with procedural strings attached. An inventor who publishes, demonstrates, or sells and then files in the United States within the year has preserved U.S. rights and forfeited most foreign rights. The interplay with PCT and Paris Convention filing is covered in International Patent Filing: The PCT, Paris Priority, National Phase, and Foreign Prosecution.

Prong (B) is narrow. The USPTO's position, stated in its first-inventor-to-file examination guidelines (78 Fed. Reg. 11059 (Feb. 14, 2013)) and at MPEP § 2153.02, is that the intervening third-party disclosure is excepted only to the extent it discloses the same subject matter the inventor disclosed; if the third party discloses more, or discloses a species where the inventor disclosed a genus, the additional or more specific material remains prior art. Courts have been equally strict about what counts as the inventor's triggering "public disclosure." In Sanho Corp. v. Kaijet Technology International Ltd., 108 F.4th 1376 (Fed. Cir. 2024), the inventor's company had sold 15,000 units of a laptop docking device in a private, non-confidential transaction a week before a third party filed a patent application describing similar technology. The patent owner argued that the sale "publicly disclosed" the subject matter under § 102(b)(2)(B), the parallel shield against earlier-filed applications, so the third party's application was not prior art. The Federal Circuit disagreed. A private sale is a "disclosure" (after Helsinn, it is prior art under § 102(a)(1)), but the added word "publicly" marks out a narrower subset: disclosures that actually put the subject matter in the public's hands. The same words, "publicly disclosed," appear in § 102(b)(1)(B), and the court drew on legislative history describing both provisions together, so the lesson applies to intervening publications as well as intervening applications. The court also noted the flip side: a sale by the inventor within the year before filing, private or public, is protected by the inventor's own grace period under § 102(b)(1)(A). Inventors who want the first-to-publish shield must disclose in a way the public can actually learn from.

Disclosures "derived" from the inventor must be proved. If a third party publishes the invention within the year, the applicant must show that the third party obtained the subject matter from the inventor. That showing is made by a declaration under 37 C.F.R. § 1.130(a) (attribution) explaining how the third party came by the information, with corroboration. Where the third party is an unknown stranger, the applicant will usually be unable to make the showing, and the publication is prior art.

Section 102(b)(2) does the corresponding work for earlier-filed applications. An earlier application is not § 102(a)(2) prior art if (A) its disclosed subject matter was obtained from the inventor, (B) the inventor publicly disclosed the subject matter before the earlier application was effectively filed, or (C) the subject matter and the claimed invention were owned by the same person or subject to an obligation of assignment to the same person no later than the claimed invention's effective filing date. Prong (C), the common-ownership exception, is the one with teeth in corporate practice: a company's own earlier-filed application cannot be used against its later-filed one under § 102(a)(2), even if the inventors differ, as long as common ownership existed at the time of the later filing. The exception extends to parties to a joint research agreement under 35 U.S.C. § 102(c). Note that prong (C) does not reach § 102(a)(1): once the earlier application publishes, it is a printed publication against everyone, including its owner, after the grace period.

The strategic conclusion is simple. File before you disclose. If you cannot, file a provisional that fully describes what you are about to disclose, and treat the grace period as insurance against the disclosure you forgot about rather than a plan you drew up. How to Prepare an Invention Disclosure for Your Patent Attorney explains what the attorney needs in order to get that provisional on file quickly.

The pre-AIA regime that still governs older patents

Patents with claims that all have effective filing dates before March 16, 2013, and there are still hundreds of thousands of them in force, are governed by the old § 102, which had seven subsections and a different philosophy. The old system was first-to-invent: the inventor's date of invention, not the filing date, was the reference point for most prior art, and an applicant could "swear behind" a reference by proving earlier conception and diligence. The subsections that matter are:

• § 102(a): the invention was known or used by others in this country, or patented or described in a printed publication anywhere, before the applicant's invention date. "Known or used" required public knowledge or use; secret knowledge by others did not count. The inventor's own prior work was not § 102(a) art, and the applicant could antedate a reference under 37 C.F.R. § 1.131 by showing conception before the reference date plus diligence to a reduction to practice, or an actual reduction to practice before the reference date.
• § 102(b): the invention was patented or described in a printed publication anywhere, or in public use or on sale in this country, more than one year before the U.S. filing date. These were the statutory bars. They applied to the inventor's own activity, could not be antedated, and were measured from the actual U.S. filing date (a foreign priority date did not help). The public use and on sale cases discussed above (Egbert, Pfaff, Medicines Co., Clock Spring) were all decided under this provision, and the AIA cases apply them because the words are the same.
• § 102(e): an application for patent by another, filed in the United States before the applicant's invention date, that later published or issued. This is the ancestor of AIA § 102(a)(2), with one big difference: under In re Hilmer, 359 F.2d 859 (CCPA 1966), a § 102(e) reference was prior art only as of its U.S. filing date, not its foreign priority date. The Hilmer rule meant a foreign applicant's U.S. patent could not reach back to its home-country filing as prior art against others, even though the same applicant could use that date to defend its own claims. The AIA abolished the rule for AIA patents through § 102(d); it still applies when the challenged patent is a pre-AIA patent.
• § 102(f): the applicant did not invent the subject matter (derivation). Replaced under the AIA by derivation proceedings under 35 U.S.C. § 135 and the inventorship requirement of 35 U.S.C. § 116.
• § 102(g): before the applicant's invention, the invention was made in this country by another who had not abandoned, suppressed, or concealed it. This was the basis for interference proceedings, in which two applicants fought over who conceived first and who was diligent, and it also functioned as a prior art category in litigation: a defendant could prove that someone else made the invention first in this country and did not abandon, suppress, or conceal it.

Under pre-AIA law, a third party's secret commercial use was not prior art against another inventor's patent (W.L. Gore), and an inventor's own secret commercial use was treated as a forfeiture under Metallizing. Pre-AIA § 103(c) also contained a common-ownership exception limited to § 102(e), (f), and (g) art and to obviousness; it did not reach anticipation. The pre-AIA rules for priority dates of § 102(e) references are the Dynamic Drinkware rules discussed above. The MPEP treats the pre-AIA subsections at §§ 2132 to 2138 (with the public use and on-sale bars at § 2133.03), and Chisum on Patents chs. 3 and 6 treat novelty and the statutory bars in detail.

For a litigator the practical difference is procedural. Against a pre-AIA patent, the patentee can defeat a § 102(a) or (e) reference by proving an earlier invention date with lab notebooks and corroborating witnesses, which turns a document fight into a credibility fight. Mahurkar v. C.R. Bard, Inc., 79 F.3d 1572 (Fed. Cir. 1996), explains how the burdens work: the challenger keeps the burden of persuasion throughout, but once it puts in a reference that predates the filing date, the patentee must come forward with evidence of an earlier invention date, and the inventor's own testimony on that point needs corroboration. Against an AIA patent, the invention date is irrelevant, and the only ways to remove a reference are to show it postdates the effective filing date, falls within a § 102(b) exception, or does not actually disclose what the challenger says it does.

What a reference must contain to anticipate

Qualifying as prior art is the threshold; anticipating is the finish line. A reference anticipates a claim under § 102 only if it discloses every element of the claim, arranged as in the claim, either expressly or inherently, and the disclosure is enabling. Each piece of that sentence carries law.

Every element, arranged as claimed. The reference must disclose all limitations in a single document or embodiment. Picking elements from different embodiments of the same reference is permitted only if the reference itself suggests combining them; otherwise the analysis belongs under § 103. Net MoneyIN, Inc. v. VeriSign, Inc., 545 F.3d 1359 (Fed. Cir. 2008), reversed an anticipation finding that had combined two separate protocols described in one reference. The classic formulation is Verdegaal Bros., Inc. v. Union Oil Co. of California, 814 F.2d 628 (Fed. Cir. 1987): each and every element as set forth in the claim must be found, expressly or inherently, in a single reference. When a reference describes a short list of options, it can still anticipate if a skilled reader would "at once envisage" the claimed combination, Kennametal, Inc. v. Ingersoll Cutting Tool Co., 780 F.3d 1376 (Fed. Cir. 2015).

Inherency. A reference discloses an element inherently if the element is necessarily present in what the reference describes, even if nobody recognized it at the time. The classic statement is Continental Can Co. USA, Inc. v. Monsanto Co., 948 F.2d 1264 (Fed. Cir. 1991): inherency may not be established by probabilities or possibilities; the missing descriptive matter must necessarily be present. Later cases confirm that recognition by skilled artisans at the time is not required, so a prior art product that inevitably had the claimed property anticipates even if the property was discovered later. In Schering Corp. v. Geneva Pharmaceuticals, Inc., 339 F.3d 1373 (Fed. Cir. 2003), an earlier patent on an antihistamine inherently anticipated a later claim to its metabolite, because patients taking the drug as the earlier patent taught necessarily produced the metabolite, even though nobody had identified it; Atlas Powder Co. v. Ireco Inc., 190 F.3d 1342 (Fed. Cir. 1999), made the same point for an explosive composition whose prior art version necessarily contained the claimed air content. Inherency is powerful against claims that recite a newly discovered result of an old process, and weak against claims that recite a feature the prior art might or might not have had.

Enablement of the reference. A prior art reference must enable the subject matter it discloses, but the standard is lower than the enablement required of the patent itself. In re Gleave, 560 F.3d 1331 (Fed. Cir. 2009), held that a reference listing a claimed oligonucleotide sequence among thousands anticipated it, even though the reference did not say what the sequence was good for, because anticipation requires only that the reference put the public in possession of the claimed subject matter, not that it disclose a use. Rasmusson v. SmithKline Beecham Corp., 413 F.3d 1318 (Fed. Cir. 2005), reaffirmed the rule that a reference need not prove efficacy to be enabling for anticipation purposes; it need only enable the skilled person to make (and, for a method, practice) the claimed invention. Amgen Inc. v. Hoechst Marion Roussel, Inc., 314 F.3d 1313 (Fed. Cir. 2003), held that an accused infringer is entitled to a presumption that both the claimed and unclaimed disclosures of a prior art patent are enabled, which the patentee may rebut, and In re Antor Media Corp., 689 F.3d 1282 (Fed. Cir. 2012), extended the presumption to non-patent publications an examiner cites. Either way, the question is whether a skilled artisan could make the invention from the reference, read with the knowledge in the art, without undue experimentation; see also In re Donohue, 766 F.2d 531 (Fed. Cir. 1985). The reference may be read in light of the knowledge of a skilled artisan to fill in details, but extrinsic evidence cannot supply a missing claim element.

Genus and species. A prior disclosure of a species anticipates a later claim to the genus that includes it; in Titanium Metals Corp. of America v. Banner, 778 F.2d 775 (Fed. Cir. 1985), a published data point inside a claimed alloy range anticipated the range. A prior disclosure of a genus anticipates a later species claim only if the genus is small enough that the skilled person would "at once envisage" each member, a test drawn from In re Petering, 301 F.2d 676 (CCPA 1962), and applied in chemical cases ever since. Large genera do not anticipate; they may render a species obvious.

If the reference falls short on any element, the analysis moves to obviousness, where the reference is combined with other art or with the knowledge of the skilled artisan under KSR International Co. v. Teleflex Inc., 550 U.S. 398 (2007), and Graham v. John Deere Co., 383 U.S. 1 (1966). Art used under § 103 must still qualify as prior art under § 102; the general knowledge of the skilled artisan is not itself a reference, but it supplies the background against which the references are read.

Proving prior art: burdens, forums, and evidence

A reference is only as good as the proof behind it. Most prior art fights that a challenger loses are not lost on the law; they are lost because nobody could prove when the document went public, whether the product on the shelf in 2014 was configured the way the expert says, or whether the witness who remembers a demonstration is telling the truth.

Who carries which burden

An issued patent is presumed valid under 35 U.S.C. § 282, and in district court and at the International Trade Commission the challenger must prove invalidity by clear and convincing evidence. Microsoft v. i4i held that the standard does not drop when the art was never before the examiner, although the jury may be told that the Patent Office never had a chance to consider it. The converse is also true: there is no extra burden when the art was before the examiner, Sciele Pharma Inc. v. Lupin Ltd., 684 F.3d 1253 (Fed. Cir. 2012). The challenger's burden includes the threshold facts: that the reference existed, what it disclosed, and when and how it became available. At the Patent Trial and Appeal Board the burden is a preponderance of the evidence in both inter partes review and post-grant review (35 U.S.C. § 316(e); 35 U.S.C. § 326(e)), which is one reason challengers with good documentary art so often prefer the Board. The Board's precedential decision in Hulu, LLC v. Sound View Innovations, LLC, IPR2018-01039, Paper 29 (PTAB Dec. 20, 2019), sets the institution-stage test for public accessibility: a reasonable likelihood, judged on the totality of the evidence, including indicia such as copyright dates, ISBNs, and publisher information.

What each forum lets you use

Three refinements matter. First, a published patent application counts as a "printed publication" for inter partes review as of its filing date when the patent statute makes it prior art as of that date: Lynk Labs, Inc. v. Samsung Electronics Co., No. 2023-2346 (Fed. Cir. Jan. 14, 2025), so an application filed before the critical date but published after it is fair game in an IPR. Second, IPR estoppel reaches only the patent-and-publication grounds a petitioner raised or reasonably could have raised, measured by what a skilled searcher conducting a diligent search would have found, with the burden on the patent owner to prove it, Ironburg Inventions Ltd. v. Valve Corp., 64 F.4th 1274 (Fed. Cir. 2023). Third, estoppel does not stop a petitioner who loses an IPR from arguing in court that the invention was in public use, on sale, or known or used by others, even if the product evidence overlaps with the paper it relied on before the Board, Ingenico Inc. v. IOENGINE, LLC, 136 F.4th 1354 (Fed. Cir. 2025). Product-based prior art is therefore the challenger's insurance policy. The strategy questions are covered in depth in Inter Partes Review Strategy: Discretionary Denial, Estoppel, and the Parallel District Court Case and Patent Post-Grant Proceedings: IPR, PGR, and Reexamination at the PTAB.

Dates, authentication, and corroboration

Documents must be authenticated under Fed. R. Evid. 901: by a witness with knowledge, by distinctive characteristics, by comparison with an authenticated specimen (the route Valve approved), or, for documents at least 20 years old found where they would be expected, under the ancient-documents provision. Some documents authenticate themselves under Fed. R. Evid. 902, including official publications, newspapers and periodicals, and certified business and electronic records. A reference offered for what it discloses is not hearsay, because nobody is offering it for the truth of what it says; a printed date offered to prove when the document went public is a different matter, and proponents typically rely on the ancient-documents exception in Fed. R. Evid. 803(16) for documents prepared before 1998, on business-records foundations, on public records, or on the residual exception in Fed. R. Evid. 807, which Valve also invoked. For archived web pages, the standard package is an affidavit from the Internet Archive's records custodian plus something independent: a second copy, a dated citation in another document, or testimony from someone who saw the page. Small alterations in a reproduction (a changed time stamp or email header) do not by themselves create a genuine dispute about what was posted, Suffolk Technologies, LLC v. AOL Inc., 752 F.3d 1358 (Fed. Cir. 2014), which held a newsgroup post publicly accessible. The companion Authenticating Website Evidence: A Practical Checklist walks through the foundation questions.

Testimony about prior uses and sales gets special skepticism. The Supreme Court warned in The Barbed Wire Patent, 143 U.S. 275 (1892), that oral recollections of old fences were a weak foundation for invalidating a patent, and the Federal Circuit has turned that caution into a corroboration requirement. Woodland Trust v. Flowertree Nursery, Inc., 148 F.3d 1368 (Fed. Cir. 1998), reversed an invalidity judgment that rested on uncorroborated testimony from one of the defendant's owners and his associates that they had used the patented freeze-protection method on Florida fern beds in the 1960s and 1970s; no physical record supported the story, and the reconstructed system shown at trial had been built in 1988. Finnigan Corp. v. International Trade Commission, 180 F.3d 1354 (Fed. Cir. 1999), extended the requirement to disinterested witnesses: corroboration is required of any witness whose testimony alone is offered to invalidate a patent. Corroboration is judged under a "rule of reason," documents made at the time count most, Sandt Technology, Ltd. v. Resco Metal & Plastics Corp., 264 F.3d 1344 (Fed. Cir. 2001), and circumstantial evidence can do the job: Ingenico upheld a public use verdict resting on circumstantial evidence that customers were encouraged to download and run a firmware utility, with user guides telling them how.

Physical products need a chain of proof of their own: when the unit was made and sold (date codes, invoices, shipping records), that its configuration has not changed since (firmware versions, part numbers, service records), and what it actually contains (a documented teardown by someone who can testify). A product that the challenger cannot date, or that might have been modified, invites a credibility fight the challenger usually loses under the clear-and-convincing standard.

Invalidity contentions and the § 282 notice

In districts with local patent rules, the accused infringer must serve invalidity contentions early, typically about 45 days after the patent owner's infringement contentions in the Northern District of California and the Eastern District of Texas. The rules require each item of prior art to be identified (for a public use or sale, the item, the date, and the people involved), a chart showing where each claim element is found, and production of the art. Amendments require a showing of good cause, which means diligence: O2 Micro International Ltd. v. Monolithic Power Systems, Inc., 467 F.3d 1355 (Fed. Cir. 2006), upheld the exclusion of theories a party sat on. Separately, § 282(c) requires written notice at least 30 days before trial of every patent and publication relied on and the name and address of every person who may be relied on as having prior knowledge, prior use, or a prior offer for sale. Expert reports under Fed. R. Civ. P. 26(a)(2) and the reliability gate of Fed. R. Evid. 702 then govern how the art is explained to the fact-finder; see Expert Depositions: Taking Apart the Opinion, Protecting Your Own Expert, and Building the Daubert Record.

Prior art during prosecution: Rule 130, Rule 131, and the duty of disclosure

Prior art arrives during prosecution in an examiner's rejection under § 102 or § 103 after the examination required by 35 U.S.C. § 131. The applicant can argue that the reference does not disclose what the examiner says, amend the claims around it, or remove the reference as prior art. Removal is where the AIA exceptions earn their keep, and the vehicle is a declaration under 37 C.F.R. § 1.130:

• Rule 130(a), attribution. The applicant shows that the cited disclosure was the inventor's own, or was obtained from the inventor, so it falls within § 102(b)(1)(A) or (b)(2)(A). An inventor's own article published ten months before filing is removed this way. A co-author who is not a named inventor needs an explanation (often that the co-author worked under the inventor's direction and did not contribute to the claimed subject matter).
• Rule 130(b), prior public disclosure. The applicant shows that the inventor publicly disclosed the subject matter before the intervening disclosure, which removes it under § 102(b)(1)(B) or (b)(2)(B). The declaration must include the earlier disclosure itself, or describe it in enough detail, so the examiner can compare the two. After Sanho, the earlier disclosure must really have been public.
• Limits. A Rule 130 declaration cannot remove a disclosure made more than a year before the effective filing date, and it is generally not the tool when the reference is a U.S. patent or application claiming the same or substantially the same invention and the applicant's real contention is that the other inventor took it; that conflict belongs in a derivation proceeding under 35 U.S.C. § 135. MPEP §§ 2155 to 2155.06 describe the practice.
• Common ownership. For the § 102(b)(2)(C) exception, a clear statement on the record that the subject matter and the claimed invention were commonly owned (or subject to an obligation of assignment to the same person) not later than the effective filing date is enough; no declaration is required (MPEP § 2154.02(c)).
• Rule 131 for pre-AIA applications. Under 37 C.F.R. § 1.131, the applicant antedates a reference by showing reduction to practice before its date, or conception before its date coupled with diligence to a later reduction to practice. Rule 131 cannot overcome a statutory bar (anything more than a year before filing) and has no role in AIA applications.

The other side of prosecution is the duty of candor. Under 37 C.F.R. § 1.56, every individual substantively involved in preparing or prosecuting an application must disclose information known to be material to patentability, and the information disclosure statement (IDS) rules in 37 C.F.R. §§ 1.97 and 1.98 set the timing and form: an IDS filed within three months of filing or before the first office action needs no fee or certification; later filings need a statement or fee, and after allowance the window narrows further; non-patent literature and foreign documents must be supplied in legible copies, with a concise explanation of relevance for anything not in English. Filing an IDS is not an admission that anything in it is material (37 C.F.R. § 1.97(h)). The sanction for withholding is unenforceability for inequitable conduct, which since Therasense, Inc. v. Becton, Dickinson & Co., 649 F.3d 1276 (Fed. Cir. 2011) (en banc), requires but-for materiality and a specific intent to deceive that is the single most reasonable inference from the evidence; gross negligence is not enough, Kingsdown Medical Consultants, Ltd. v. Hollister Inc., 863 F.2d 867 (Fed. Cir. 1988), and the defense must be pleaded with the particularity that Exergen Corp. v. Wal-Mart Stores, Inc., 575 F.3d 1312 (Fed. Cir. 2009), demands under Fed. R. Civ. P. 9(b).

The information inventors most often fail to disclose is their own: the trade show, the pilot, the early sales. Those events are frequently the most material prior art in the file, and they are exactly what an accused infringer will find in discovery. Disclose them, explain any that fall within the grace period, and remember that a patent owner who learns of a problem after issuance can ask the Office to consider it through supplemental examination under 35 U.S.C. § 257 before anyone sues. Third parties have a prosecution role too: anyone may submit printed publications in a pending application under the preissuance submission procedure of 35 U.S.C. § 122(e), within the statutory window, and anyone may cite prior art in an issued patent's file under 35 U.S.C. § 301. For the conduct side in depth, see Inequitable Conduct in Patent Prosecution: Navigating the Atomic Bomb of Patent Law and Maintaining the Duty of Candor to Avoid Inequitable Conduct: A Practical Checklist.

Strategy for each side

For inventors and patent owners

1. Keep a disclosure calendar from day one. Record every event that could be a disclosure: talks, posters, demos, investor meetings, beta programs, quotes, purchase orders, crowdfunding pages, app store listings, regulatory filings, and product manuals. The first public event sets the one-year U.S. deadline and, for most foreign rights, ends them that day.
2. File before you show. A provisional application under 35 U.S.C. § 111(b) is inexpensive and secures a date, but only for what it actually describes. In New Railhead Manufacturing, L.L.C. v. Vermeer Manufacturing Co., 298 F.3d 1290 (Fed. Cir. 2002), the provisional did not describe the claimed angled drill bit, the claims fell back to the later filing date, and the patentee's own sales more than a year before that date invalidated them. Write the provisional as if it were the only document you will ever get.
3. Put agreements in place before demonstrations. A nondisclosure agreement converts a viewing into a confidential disclosure, and the cases (Motionless Keyboard, Dey, Bernhardt, L.L.C. v. Collezione Europa USA, Inc., 386 F.3d 1371 (Fed. Cir. 2004), where access to a pre-market furniture showing was tightly controlled) show that informal confidentiality can count too. But an NDA does not convert a sale into a non-sale; Helsinn says so. For drafting, see Drafting Enforceable Non-Disclosure Agreements for Technology Transactions.
4. Run beta programs as experiments, on paper and in fact. Tie the test plan to the claimed features, keep control of the units, collect data, impose confidentiality, charge nothing (or cost only), set an end date, and get the units back. Do not call a commercial deal a "pilot"; Sunoco shows that courts read the contract, not the label.
5. Structure manufacturing as services. Keep title to the goods, deny the contract manufacturer any right to sell to others, and avoid commercial-quantity purchase orders before filing (Medicines Co.; Hamilton Beach).
6. Decide early between patent and trade secret for processes. Selling product made by a secret process starts the clock on any process patent (Celanese). A company that chooses secrecy should document its use, because a good-faith commercial user may have a prior commercial use defense under 35 U.S.C. § 273 against a later patentee.
7. Disclose your own history to the examiner and use Rule 130 where it fits. The art you hide is the art a defendant will find.
8. When enforcing, audit before you sue. Pull your own launch history, archived pages, manuals, and sales records, and compare them with the effective filing date of every claim you plan to assert. An on-sale or public use problem discovered by the defendant after you file suit becomes a fee-shifting argument under 35 U.S.C. § 285. See Do You Have to Enforce Your Patent? Duty, Demand Letters, and the Cost of Doing Nothing.

For challengers and accused infringers

1. Start with the patent owner's own history. The most dangerous prior art is usually the patentee's: trade show booths, press releases, product launch dates, investor presentations, SEC filings, crowdfunding campaigns, archived product pages, user manuals, and regulatory filings that describe the product (equipment authorization filings and medical device clearance summaries often include photographs, diagrams, and dates).
2. Attack the dates claim by claim. Check whether each asserted claim is actually supported by every application in the priority chain. A claim that loses its provisional date can be swallowed by the patentee's own sales (New Railhead).
3. Search all three kinds of art. Patents and published applications (by classification and keyword, in multiple languages), non-patent literature (journals, conference proceedings, theses, standards submissions, technical reports, archived web pages), and products (catalogs, manuals, teardowns, distributor records).
4. Pick the forum to fit the art. Documentary art plays well at the Board under a preponderance standard; product, public use, and on-sale art must be litigated in court (or in a PGR within nine months of grant) under the clear-and-convincing standard. Keep Ingenico in mind when sequencing: product art survives IPR estoppel. The procedure is laid out in Filing or Defending an Inter Partes Review: A Practical Guide.
5. Take the on-sale and public use discovery seriously. Use document requests under Fed. R. Civ. P. 34, a corporate deposition under Fed. R. Civ. P. 30(b)(6) on pre-filing marketing and sales, and subpoenas under Fed. R. Civ. P. 45 to customers, distributors, trade show organizers, and former employees. Ask for the first quote, the first purchase order, the first shipment, and the first demonstration, by product version.
6. Corroborate everything. Pair every witness with documents, and every document with a witness who can authenticate it.
7. Serve complete contentions early and amend diligently (O2 Micro), and give the § 282 notice even when you think the contentions already did the job.

What it costs and how long it takes

The numbers vary widely by technology and market, but some rough orders of magnitude help with budgeting. A professional patentability search for a single invention often runs in the low thousands of dollars. A serious invalidity search for a litigated patent, covering patents, non-patent literature, and foreign-language art, commonly costs several thousand to tens of thousands of dollars, and a product prior art investigation with subpoenas, depositions, and a teardown costs more. The USPTO's own fees for an inter partes review petition run into the tens of thousands of dollars before any attorney or expert time (the current schedule is at 37 C.F.R. § 42.15), and total spending through a final written decision commonly reaches several hundred thousand dollars according to the AIPLA economic surveys. Timing is statutory at the Board: an institution decision within three months after the patent owner's preliminary response is filed (or the deadline for it passes) (35 U.S.C. § 314(b)), and a final written decision within one year of institution, extendable by up to six months for good cause. In district court, invalidity is litigated alongside everything else, and a case that reaches trial in a busy patent docket usually takes two to three years.

Common mistakes

• Treating the grace period as a plan. It covers one year, only in the United States and a few other countries, and only the inventor's own disclosures (and, narrowly, the same subject matter disclosed by others afterward).
• Assuming a confidential deal is not a sale. After Helsinn and Celanese, secret sales and secret commercial exploitation count against the seller.
• Calling a sale a pilot. Sunoco and Clock Spring turned on what the documents and the purpose actually were, not what anyone called them.
• Demonstrating at a trade show without filing first. Minerva is the cautionary tale, and the brochure handed out at the booth is a printed publication as well (see GoPro, Inc. v. Contour IP Holding LLC, 908 F.3d 690 (Fed. Cir. 2018), holding a catalog distributed at a dealer trade show publicly accessible).
• Filing a thin provisional. A placeholder that does not support the claims you later write protects nothing.
• Relying on an undated or unauthenticated web page. The challenger must prove the date and the accessibility; a screenshot with no provenance is an invitation to exclusion.
• Building an invalidity case on memory. Uncorroborated testimony of a prior use fails (Woodland Trust, Finnigan), no matter how sincere.
• Bringing a public use or sale theory to an IPR. The Board cannot hear it under § 311(b), although the manual or brochure that describes the product may qualify as a printed publication.
• Running the search under the wrong statute. A foreign public use is prior art against an AIA patent but not against a pre-AIA patent, and the invention date matters only under pre-AIA law.
• Hiding your own history from the examiner. It is the most material art in many files, and withholding it turns a validity problem into an unenforceability problem.

Worked example: the trade show demo fourteen months before filing

Kestrel Robotics builds PerchDock, a weatherproof dock that swaps batteries on industrial inspection drones without a human on site. Here is its history, measured against the provisional application it finally files on March 9, 2026.

Step 1: pick the statute. Every claim has a post-2013 effective filing date, so this is an AIA application. Invention dates are irrelevant, and foreign activity would count as much as domestic.

Step 2: find the grace-period line. One year before March 9, 2026 is March 9, 2025. Everything Kestrel did before that date is prior art against Kestrel.

Step 3: classify the January events. The booth demonstration is Minerva almost exactly: working devices shown to the interested trade, for days, with no confidentiality. The spec sheet handed out at the booth is a printed publication, as the catalog in GoPro was, and the posted video is publicly available. Whatever the audience could see or read about the dock's architecture and latch is now prior art. Kestrel's engineers point out that the battery-alignment logic ran inside a sealed housing. That argument is weaker than it sounds: Egbert and Hall v. Macneale held hidden features of a device in public use to be in public use, and Sanho reiterated that a public commercial use can invalidate even when it does not reveal every feature. Kestrel should assume the January configuration of the dock, inside and out, is prior art.

Step 4: classify the reservation page. Under Group One, the question is whether a customer could accept the page's terms and form a contract. A fixed price, a defined product, a delivery window, and a checkout that took money look like offers, and the accepted deposits look like contracts. The working prototypes at the show make the product ready for patenting. The February page is an on-sale event for the version offered.

Step 5: the utility evaluation. It does not matter whether the April deal was experimental, because it falls within the year and was Kestrel's own disclosure. (It would matter enormously abroad, and it would matter at home if Kestrel had waited one more month to file.)

Step 6: Halcyon's application. For the dock and latch, § 102(b)(2)(B) would exclude Halcyon's application to the extent it describes what Kestrel publicly disclosed before June 2, 2025, but that is cold comfort, because Kestrel's own January disclosures already defeat those claims. For battery pre-conditioning, Halcyon's application is prior art as of June 2, 2025 to whatever extent it describes the routine. Kestrel cannot remove it with a Rule 130(b) declaration (it disclosed nothing about pre-conditioning before June 2025) and has no evidence for a Rule 130(a) showing that Halcyon got the idea from Kestrel.

Step 7: salvage. The magnetic alignment collar was never disclosed and may be patentable if it is not obvious over the January docks, Halcyon's application, and the rest of the art. Pre-conditioning claims survive only to the extent they recite specifics that Halcyon does not describe. Kestrel should draft narrow claims around those improvements, make sure the provisional describes them fully, and file an international application within twelve months to preserve foreign rights in the undisclosed improvements. The original dock is unpatentable in absolute-novelty countries, and the twelve-month grace periods available in a few countries have also run. The dock's appearance, shown at the trade show and in the video more than a year before filing, cannot support a U.S. design patent either, because design patents are subject to the same novelty conditions (35 U.S.C. § 171).

Step 8: what would have worked. A thorough provisional filed in December 2024 would have put every one of these events after the effective filing date. Even a filing in late 2025, inside the year, would have saved the U.S. position (the grace period covers Kestrel's own demonstration and offers), although not foreign rights in the original dock.

The other side. If Kestrel later sues Halcyon on a collar patent, Halcyon's counsel will start where this example started: Kestrel's own history. Was a collar on the evaluation units, and if so, when was it installed? Did any investor deck, job posting, or firmware release note describe the collar before March 9, 2026? Does the provisional actually describe what the asserted claims recite? Then the search moves outward, to third-party docks, alignment mechanisms in other robotic charging systems, and archived product pages, which is the subject of the companion Finding, Qualifying, and Using Prior Art: A Practical Guide.

Frequently asked questions

Does showing my invention to potential investors start the clock? Not necessarily. A private showing to a few people, under an NDA or circumstances implying confidentiality, is generally not a public use (Motionless Keyboard). A pitch deck emailed without restriction to dozens of recipients is riskier, because a document distributed without confidentiality to people who could understand it can be a printed publication. Use NDAs, limit technical detail in decks, and file first when you can.

If I sell under an NDA, is the invention still "on sale"? Yes. Helsinn held that a confidential sale is still a sale, and Celanese applied the same rule to products made by a secret process. Confidentiality matters to public use and to whether a transaction is commercial (Medicines Co.), but it does not make a real sale disappear.

Is a crowdfunding campaign or preorder page an offer for sale? Often, yes. Courts apply contract law, so the answer turns on whether the page made terms a customer could accept. Treat any page that takes money for a defined product as an offer, and treat the campaign video as a public disclosure in any event.

Does the U.S. grace period protect me in other countries? Mostly no. The European Patent Convention allows only narrow exceptions (evident abuse and certain officially recognized exhibitions, within six months), and the countries that have twelve-month grace periods, such as Japan and Korea, attach procedural requirements. If foreign rights matter, file before any disclosure, then use the twelve-month Paris Convention priority period to file abroad.

A competitor published my idea after I posted about it. Am I protected? Possibly, under § 102(b)(1)(B), but only for the same subject matter you publicly disclosed first, and only if your disclosure was genuinely public (Sanho). Anything the competitor added remains prior art. File quickly so the question does not arise.

Can an inter partes review be based on a product sold before the critical date? No. Section 311(b) limits IPRs to patents and printed publications. A product's manual, brochure, or catalog can qualify as a printed publication (Weber; GoPro), and the product itself can be used in district court even after an unsuccessful IPR (Ingenico).

Can my own earlier patent application be used against my later one? Yes, in two ways. Once it publishes, it is a printed publication, and after the one-year grace period runs it is prior art under § 102(a)(1). Before then, an application naming a different inventive entity can be § 102(a)(2) art unless an exception applies, most usefully the common-ownership exception of § 102(b)(2)(C). Continuation and priority strategy should account for both.

Does a competitor's secret use of my invention before my filing invalidate my patent? Generally no. A third party's secret commercial use is not prior art against another inventor (W.L. Gore), but that competitor may have a prior commercial use defense under § 273, so its existing operations may be shielded even if your patent is valid.

Practical takeaways

• Read the priority chain first: the AIA governs claims with effective filing dates on or after March 16, 2013, and the choice of statute changes what counts.
• Public accessibility, not printing, makes a printed publication; prove the date and the path an interested person would have taken to find it.
• A public use is any non-confidential use by others or accessible use by the inventor, hidden features included; experimental use requires control, records, and testing of the claimed features.
• A sale counts if it is a commercial offer under contract law and the invention is ready for patenting, even if it is secret.
• The one-year grace period protects the inventor's own disclosures in the United States only, and the shield against intervening third-party disclosures requires a genuinely public first disclosure.
• Earlier-filed U.S. and PCT applications are prior art as of their effective filing dates, including foreign priority dates under the AIA; common ownership removes them under § 102(a)(2) but not once they publish and the year runs.
• Anticipation needs every element in one enabling reference, expressly or inherently; everything else is an obviousness argument.
• Choose the forum by the art: documents fit the PTAB's preponderance standard; products, uses, and sales belong in court under the clear-and-convincing standard.
• Corroborate oral testimony and authenticate archived pages before you rely on them.
• Inventors: file before disclosing, write real provisionals, paper confidentiality, and tell the examiner about your own history.

This document is general information, not legal advice for any particular situation; the law changes, and the facts matter.

Related Documents

Related Guides

• Finding, Qualifying, and Using Prior Art: A Practical Guide: the step-by-step companion to this article, from search strategy to invalidity contentions and trial proof.
• Filing or Defending an Inter Partes Review: A Practical Guide: how petitions built on patents and printed publications are filed, instituted, and tried.
• Patent Basics: A Plain-English Guide: the vocabulary of claims, filing dates, and patent rights for readers new to the system.

Related Checklists

• Prior Art Qualification Checklist: A Practical Checklist: a reference-by-reference checklist for deciding whether a document, use, or sale qualifies and can be proved.
• Maintaining the Duty of Candor to Avoid Inequitable Conduct: A Practical Checklist: IDS and disclosure practice for applicants who want enforceable patents.
• Authenticating Website Evidence: A Practical Checklist: the foundation steps for archived pages and screenshots.
• International Patent Filing Checklist: A Practical Checklist: deadlines and decisions for preserving foreign rights before and after a disclosure.

Related Toolkits

• Prior Art Toolkit: Search Protocols, Invalidity Charts, and On-Sale Bar Investigations: templates for search logs, claim charts, discovery requests, and corroboration files.

Related Articles

• Overcoming Obviousness Rejections: A Comprehensive Guide to Section 103 Analysis: what happens when the art qualifies but does not anticipate.
• Inter Partes Review Strategy: Discretionary Denial, Estoppel, and the Parallel District Court Case: forum choice and estoppel for challengers holding both paper and product art.
• Patent Post-Grant Proceedings: IPR, PGR, and Reexamination at the PTAB: the three administrative routes for challenging an issued patent.
• Inequitable Conduct in Patent Prosecution: Navigating the Atomic Bomb of Patent Law: the consequences of withholding material prior art.
• How to Prepare an Invention Disclosure for Your Patent Attorney: what counsel needs to file a provisional before the trade show.
• International Patent Filing: The PCT, Paris Priority, National Phase, and Foreign Prosecution: why absolute novelty abroad makes the U.S. grace period a poor plan.
• How to Read a Patent: Claims, Specification, and Prosecution History: finding the priority chain and the claim language that prior art must meet.
• Capturing the Web: A Practitioner's Guide to Authenticating Website Screenshots as Evidence in Federal Court: the evidence law behind archived web pages.
• Drafting Enforceable Non-Disclosure Agreements for Technology Transactions: the agreements that keep demonstrations confidential.
• Expert Depositions: Taking Apart the Opinion, Protecting Your Own Expert, and Building the Daubert Record: preparing and attacking the technical experts who explain prior art.
• Indirect and Divided Patent Infringement: Inducement, Contributory Liability, and the Akamai Problem: the infringement side of the cases in which invalidity defenses are usually raised.
• Do You Have to Enforce Your Patent? Duty, Demand Letters, and the Cost of Doing Nothing: what a patent owner should check, including its own prior art, before sending a demand.