Prior Art Qualification Checklist: A Practical Checklist

An old manual, a conference poster, a booth at a trade show, a purchase order for 500 units: any one of them can end a patent, and any one of them can turn out to be nothing at all. The difference is rarely the content. It is whether someone can prove that the thing fits a category of 35 U.S.C. § 102, before the right date, with no exception that takes it out, using evidence a court or the Patent Trial and Appeal Board will accept. This checklist breaks that proof into the questions you actually have to answer, in the order you should answer them.

The short answer

Every candidate reference passes through seven gates, and it fails if it stalls at any of them:

Date the claim. Determine each claim's effective filing date and whether the America Invents Act (AIA) or the pre-AIA version of § 102 governs.
Classify the reference. Patent, printed publication, public use, sale, other public availability, or earlier-filed U.S. application, and whose activity it was.
Meet the category's own test. Public accessibility for documents; non-confidential use for uses; a commercial offer of something ready for patenting for sales.
Rule out what takes it out. The one-year grace period, derivation, prior public disclosure by the inventor, common ownership, and (for the patent owner's own uses and sales) the experimental use negation.
Confirm the content. Every claim element, arranged as claimed, expressly or inherently, in an enabling disclosure; otherwise plan an obviousness use.
Prove it. Authenticate documents, get the date in without a hearsay problem, corroborate every witness, and lock down product provenance.
Match it to the forum. Inter partes review takes only patents and printed publications; uses and sales belong in court, at the ITC, or in post-grant review.

The doctrine behind each gate is explained in Prior Art Under the America Invents Act: Section 102, the On-Sale Bar, Public Use, and the One-Year Grace Period. The search and litigation sequence is in Finding, Qualifying, and Using Prior Art: A Practical Guide, and the forms that implement this checklist (search logs, qualification sheets, claim charts, and on-sale discovery requests) are in the Prior Art Toolkit: Search Protocols, Invalidity Charts, and On-Sale Bar Investigations.

How to use this checklist

Run it once per reference, per patent (or per family, if the claims share a priority chain). Mark each item Yes, No, or Unknown, and for every Unknown write down who will find out and how. The answers go in the qualification record near the end of this document, which becomes the backbone of contentions, petitions, and expert reports.

Challengers and accused infringers run it forward, to decide which references are worth the cost of proving.
Patent owners run it in reverse: every item a challenger must satisfy is an item you can attack (Phase 14 collects the attack points).
Prosecutors run Phases 1 through 5 and 10 when a reference is cited in a rejection or is about to go into an information disclosure statement.
Inventors and startups run Phases 6, 8, and 15 on their own history before filing, because the most dangerous prior art is usually the inventor's own.

Two working rules apply throughout. First, record the evidence for each answer, not just the answer, because a conclusion you cannot prove is worth nothing under a clear-and-convincing standard. Second, qualify every reference against both sides' claim constructions; a reference that anticipates under one reading may miss under the other.

Phase 1: Fix the claims and their dates

List every claim in play (asserted, challenged, rejected, or about to be filed) and break each independent claim into lettered elements: 1[a], 1[b], 1[c]. Note: Use the same lettering in the search plan, the charts, the contentions, and the expert reports. A chart that letters elements differently from the contentions is an avoidable credibility problem.
Record the working construction of every term that could decide anticipation, and the other side's construction if it differs. Note: Courts construe claims under Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005) (en banc), and the Board has applied the same standard in AIA trials since November 2018 under 37 C.F.R. § 42.100(b). The construction work itself is covered in the Claim Construction Checklist: A Practical Checklist.
Pull the complete priority chain: every provisional, parent, continuation, foreign priority application, and PCT application, with filing dates and the benefit or priority claims as actually made.
Determine each claim's effective filing date under 35 U.S.C. § 100(i): the actual filing date, or the date of the earliest application that supports the claim under 35 U.S.C. § 112(a) and is properly claimed under 35 U.S.C. § 119, 35 U.S.C. § 120, or 35 U.S.C. § 365. Note: Written description support must run through every link of the chain, Lockwood v. American Airlines, Inc., 107 F.3d 1565 (Fed. Cir. 1997). A claim that loses its provisional date can fall to the patent owner's own sales in the gap, as in New Railhead Manufacturing, L.L.C. v. Vermeer Manufacturing Co., 298 F.3d 1290 (Fed. Cir. 2002). Once a challenger puts in art that predates the actual filing date, the patent owner must come forward with evidence that the earlier application supports the claim, while the burden of persuasion stays with the challenger: Technology Licensing Corp. v. Videotek, Inc., 545 F.3d 1316 (Fed. Cir. 2008); PowerOasis, Inc. v. T-Mobile USA, Inc., 522 F.3d 1299 (Fed. Cir. 2008).
Decide whether the AIA or pre-AIA § 102 governs, and write the answer at the top of the file. Note: The AIA applies if the application contains, or at any time contained, a claim with an effective filing date on or after March 16, 2013 (AIA § 3(n)(1), Pub. L. 112-29). The choice is made application by application, while effective filing dates are determined claim by claim. In a "transition" application that also contains or contained a claim entitled to an earlier date, AIA § 3(n)(2) applies pre-AIA § 102(g) as well. MPEP § 2159 sets out the USPTO's approach.
Compute and record the critical dates for each claim. Note: Under the AIA there are two: the effective filing date (third-party disclosures and earlier-filed applications before it are presumptively prior art) and the date one year earlier (anything before it is prior art no matter who made it). Because an AIA effective filing date can be a foreign priority date, the one-year grace period runs back from that date. Under pre-AIA law, the § 102(b) critical date is one year before the earliest U.S. filing date to which the claim is entitled (a foreign priority date does not move it), and the date of invention governs § 102(a), (e), and (g).
Flag every claim whose priority looks vulnerable, and move the patent owner history investigation (Phases 6 and 8) to the front of the line for those claims. Note: A priority attack combined with the patent owner's own launch activity is often the cheapest and strongest invalidity theory in the case.

Phase 2: Classify the reference

List every category the reference fits: patented; described in a printed publication; in public use; on sale; otherwise available to the public (all under § 102(a)(1)); described in an earlier-filed U.S. patent, published U.S. application, or published PCT application naming another inventor (under § 102(a)(2)); and, for pre-AIA claims, known or used by others in this country, pre-AIA § 102(e), or prior invention under pre-AIA § 102(g). Note: One source often fits several categories, each with different proof and a different forum. A product's manual may be a printed publication usable in an inter partes review; the product it describes is public use or on-sale art usable only in court, at the ITC, or in a post-grant review. Record every category now so the backup theory is not lost.
Record whose activity it was: the inventor or patent owner, someone who obtained the subject matter from the inventor, or an independent third party. Note: The answer decides which § 102(b) exceptions are available, whether experimental use can apply (it is the inventor's doctrine), and whether secret commercial activity counts. An inventor's own secret commercial exploitation forfeits the right to patent, Metallizing Engineering Co. v. Kenyon Bearing & Auto Parts Co., 153 F.2d 516 (2d Cir. 1946); a third party's secret use generally does not count against someone else's patent, W.L. Gore & Associates, Inc. v. Garlock, Inc., 721 F.2d 1540 (Fed. Cir. 1983).
Record where it happened. Note: The AIA has no geographic limits. Pre-AIA public use and on-sale activity counted only "in this country," as did pre-AIA prior knowledge or use by others; patents and printed publications counted anywhere.
Decide how you will use it: as an anticipating reference, as a primary or secondary reference for obviousness under 35 U.S.C. § 103, or both. Note: Qualification is the same either way. What changes is the content analysis in Phase 11. Art used for obviousness must still qualify under § 102; the background knowledge of the skilled artisan is not a reference, although it is the lens through which references are read.

Phase 3: Patents and published applications

For use under § 102(a)(1), record the date the document became available to the public: the issue date of a U.S. patent, the publication date of a published application, and for a foreign document the date its contents were open to public inspection. Note: A patent granted in secret is not "patented" prior art until the public could learn its contents (MPEP § 2126). In practice nearly every useful patent document also qualifies as a printed publication once it publishes, and that date controls.
For use under § 102(a)(2), confirm three things: (1) the document is a U.S. patent, a published U.S. application, or a published PCT application designating the United States; (2) it names another inventor, meaning its inventive entity differs from the claim's by at least one person; and (3) it was effectively filed before the claim's effective filing date. Note: Under § 102(d), the reference is effectively filed, for any subject matter it describes, as of the earliest application in its chain (foreign applications included) that describes that subject matter (MPEP §§ 2154.01(b) and 2154.01(c)).
Chart every relied-on passage to the priority document that is supposed to supply the early date. Note: For pre-AIA § 102(e) art, a reference patent gets its provisional date only if the provisional also supports at least one of the reference's claims, Dynamic Drinkware, LLC v. National Graphics, Inc., 800 F.3d 1375 (Fed. Cir. 2015) (refining In re Giacomini, 612 F.3d 1380 (Fed. Cir. 2010)), and a foreign priority date does not count at all, In re Hilmer, 359 F.2d 859 (CCPA 1966). The AIA text asks only whether the earlier application "describes the subject matter," but patent owners still argue Dynamic Drinkware, so show claim support as a fallback when you can.
Confirm the reference was actually published or issued. Note: An application that never published stays confidential under 35 U.S.C. § 122 and is not prior art under either subsection while it remains so.
Check whether the reference and the claim were commonly owned, or subject to an obligation of assignment to the same person, not later than the claim's effective filing date (see Phase 10).
Look for admissions in the patent itself. Note: A statement in the patent that something is prior art binds the patent owner for anticipation and obviousness, Constant v. Advanced Micro-Devices, Inc., 848 F.2d 1560 (Fed. Cir. 1988). At the Board, applicant-admitted prior art can show the general knowledge of a skilled artisan but cannot itself be the basis of a ground, Qualcomm Inc. v. Apple Inc., 24 F.4th 1367 (Fed. Cir. 2022).
If the reference will be used in an inter partes review, confirm the date the Board will use. Note: A published application can be relied on as of its filing date where the statute makes it prior art as of that date, Lynk Labs, Inc. v. Samsung Electronics Co., No. 2023-2346 (Fed. Cir. Jan. 14, 2025), a case decided under pre-AIA § 102(e)(1).

Phase 4: Printed publications and public accessibility

Identify exactly what the document is and how it reached the public: journal article, book, thesis, conference paper or poster, slide deck, manual, catalog, data sheet, standards contribution, government filing, web page, preprint, code repository, or video.
Prove either actual dissemination or availability plus a path to it. The test is whether a person interested and ordinarily skilled in the subject matter, exercising reasonable diligence, could have located the document before the critical date, In re Wyer, 655 F.2d 221 (CCPA 1981). Note: Once accessibility is shown, nobody has to prove that anyone actually read the document, and evidence of a routine practice (such as a library's standard cataloging procedure) can establish the date, Constant; In re Hall, 781 F.2d 897 (Fed. Cir. 1986).
For library and archival materials, obtain the catalog record, the accession or receipt stamp, the date of cataloging, and testimony or records about shelving practice. Note: Compare Hall (dissertation indexed and shelved: accessible), In re Bayer, 568 F.2d 1357 (CCPA 1978) (thesis available only to the graduate committee: not accessible), and In re Cronyn, 890 F.2d 1158 (Fed. Cir. 1989) (theses indexed only by student name: not accessible).
For presentations, posters, and displays, record how long the material was shown, the expertise of the audience, whether copying was restricted or expected not to occur, and how easily it could have been copied. Note: Those are the factors of In re Klopfenstein, 380 F.3d 1345 (Fed. Cir. 2004). A conference paper delivered to interested attendees, with copies handed out on request without restriction, was a printed publication in Massachusetts Institute of Technology v. AB Fortia, 774 F.2d 1104 (Fed. Cir. 1985).
For limited distributions, identify the recipients, their number, their place in the art, and any express or implied expectation of confidentiality. Note: A distribution to interested members of the art can suffice, Samsung Electronics Co. v. Infobridge Pte. Ltd., 929 F.3d 1363 (Fed. Cir. 2019); monographs shared with a few companies under academic norms of confidentiality did not, Cordis Corp. v. Boston Scientific Corp., 561 F.3d 1319 (Fed. Cir. 2009); and materials shown at industry meetings require findings on audience size, expectations, and who attended, Medtronic, Inc. v. Barry, 891 F.3d 1368 (Fed. Cir. 2018).
For online material, show that the page or file was indexed by search engines, linked from places the art would look, or announced to the interested public. Note: A paper on a personal web page with no evidence of indexing failed in Blue Calypso, LLC v. Groupon, Inc., 815 F.3d 1331 (Fed. Cir. 2016); a report in a repository searchable only by author and year failed in Acceleration Bay, LLC v. Activision Blizzard Inc., 908 F.3d 765 (Fed. Cir. 2018); an article on a site well known to the field succeeded in Voter Verified, Inc. v. Premier Election Solutions, Inc., 698 F.3d 1374 (Fed. Cir. 2012); and a paper posted briefly on an unindexed FTP server for peer review raised a genuine factual dispute in SRI International, Inc. v. Internet Security Systems, Inc., 511 F.3d 1186 (Fed. Cir. 2008).
For manuals, catalogs, data sheets, and trade show handouts, establish who received them, when, and on what terms. Note: Operating manuals delivered to purchasers were printed publications; the court did not need to decide whether ten or forty customers received them, held that no minimum number of recipients is required, and treated the manuals' copyright notice as no confidentiality obligation, Weber, Inc. v. Provisur Technologies, Inc., 92 F.4th 1059 (Fed. Cir. 2024). A catalog distributed at a dealer trade show was accessible in GoPro, Inc. v. Contour IP Holding LLC, 908 F.3d 690 (Fed. Cir. 2018), and a dated catalog collected at a major trade show, backed by two witnesses, was accessible in Nobel Biocare Services AG v. Instradent USA, Inc., 903 F.3d 1365 (Fed. Cir. 2018), where the catalog came from the inventor's own company.
For government postings, look for a Federal Register notice or other public pointer to the material, as in Jazz Pharmaceuticals, Inc. v. Amneal Pharmaceuticals, LLC, 895 F.3d 1347 (Fed. Cir. 2018).
For standards, treat each separately authored specification or contribution as its own reference unless one incorporates another. Note: The GSM standard was accessible but could not anticipate as a single reference in Kyocera Wireless Corp. v. International Trade Commission, 545 F.3d 1340 (Fed. Cir. 2008).
For a work registered with the Copyright Office, prove when it became findable, not when it was registered. Note: In In re Lister, 583 F.3d 1307 (Fed. Cir. 2009), a registered manuscript became accessible only when it entered databases that allowed keyword searches of titles, and the rejection fell because nobody proved that happened before the critical date.
Record the earliest provable date of accessibility, which may differ from the date printed on the document. Note: A printed date is relevant but not dispositive (Nobel Biocare). Beware print-on-demand copies: in VidStream LLC v. Twitter, Inc., 981 F.3d 1060 (Fed. Cir. 2020), the petitioner's copy of a 2011 book bore a 2015 printing stamp, and the earlier date was established with a certified Library of Congress copy, the Copyright Office registration certificate, and a library science expert's analysis of the book's catalog records. MPEP §§ 2128 to 2128.02 summarize the USPTO's view.

Phase 5: Web pages and archived files

Treat the page and the file as two references with two dates. Record the URL of the page that linked to a PDF and the URL of the PDF itself, and check the capture dates of each. Note: An archived product page from 2016 that links to a manual proves little about the manual unless the manual itself was captured, or the link resolved, before the critical date.
Pull the full list of Wayback Machine captures for each URL and record the 14-digit capture timestamps. Note: The capture history also shows whether the content changed between captures, which matters when the patent owner argues that the version you rely on postdates the critical date.
Choose an authentication route under Fed. R. Evid. 901 before relying on the capture: an affidavit or testimony from the Internet Archive, a witness who saw or downloaded the page at the time, comparison with an authenticated copy, or circumstantial evidence. Note: The Federal Circuit approved authentication by comparison with copies of the same article found in the patent owner's own certified file histories in Valve Corp. v. Ironburg Inventions Ltd., 8 F.4th 1364 (Fed. Cir. 2021). Other courts differ on how much is needed: archive screenshots were excluded without testimony from someone with knowledge of the archive's reliability in Specht v. Google Inc., 747 F.3d 929 (7th Cir. 2014), and admitted on testimony from an Internet Archive employee in United States v. Gasperini, 894 F.3d 482 (2d Cir. 2018).
Capture the material yourself in a forensically sound way (full page, URL, date and time, hash values) and consider a certification under Fed. R. Evid. 902(13) or (14) for your own captures. Note: The mechanics are in Authenticating Website Evidence: A Practical Checklist.
Separate existence from accessibility. A capture proves that the page existed at a public address on a date; pair it with evidence that an interested person could have found it (links, search indexing, distribution, or announcements), because Blue Calypso still applies.
Plan the hearsay route for any date printed on the page itself: business records under Fed. R. Evid. 803(6), ancient documents under Rule 803(16) (only for documents prepared before January 1, 1998), or the residual exception in Fed. R. Evid. 807. Note: At the Board, the Federal Rules of Evidence apply under 37 C.F.R. § 42.62, and an objection must be made within the short windows of 37 C.F.R. § 42.64 or it is waived; the proponent may answer a timely objection with supplemental evidence. For the full analysis, see Capturing the Web: A Practitioner's Guide to Authenticating Website Screenshots as Evidence in Federal Court.
For code, check the source of every timestamp. A commit date is set by the committer's machine and can be edited; release records in package registries, archived repository snapshots, and third-party mirrors provide independent dates.

Phase 6: Public use

Identify what was used, by whom, where, when, and for how long, and confirm that the thing used embodied every element of the claim. Note: Hidden features count. The corset steel worn under clothing in Egbert v. Lippmann, 104 U.S. 333 (1881) and the concealed bolts of the safes in Hall v. Macneale, 107 U.S. 90 (1883) were in public use. The question is whether the device in use embodied the claim, not whether observers could see every element.
Decide whether the use was accessible to the public or commercially exploited, the test of Invitrogen Corp. v. Biocrest Manufacturing, L.P., 424 F.3d 1374 (Fed. Cir. 2005).
Record every confidentiality term: written NDAs, consent forms, employment obligations, and confidentiality implied by the relationship and by the inventor's control over access. Note: Express agreements are not required. Showing a puzzle to close colleagues while keeping control of it was private use in Moleculon Research Corp. v. CBS, Inc., 793 F.2d 1261 (Fed. Cir. 1986), and showing a prototype to a select group with controlled access supported an implied understanding of confidentiality in American Seating Co. v. USSC Group, Inc., 514 F.3d 1262 (Fed. Cir. 2008). A third party's clinical study run under confidentiality terms could not be held a public use on summary judgment in Dey, L.P. v. Sunovion Pharmaceuticals, Inc., 715 F.3d 1351 (Fed. Cir. 2013).
Look for the opposite: use by others under no limitation or restriction. Note: A kaleidoscope shown to 20 to 30 party guests with no effort at secrecy was in public use in Beachcombers International, Inc. v. WildeWood Creative Products, Inc., 31 F.3d 1154 (Fed. Cir. 1994), and a demonstration to university computing staff who were never told of any confidentiality requirement was a public use in Netscape Communications Corp. v. Konrad, 295 F.3d 1315 (Fed. Cir. 2002).
For demonstrations, separate operation from display. Note: Working prototypes shown to the trade at an industry meeting without restriction were in public use in Minerva Surgical, Inc. v. Hologic, Inc., 59 F.4th 1371 (Fed. Cir. 2023); a keyboard prototype displayed to investors, mostly under NDAs, without being connected to a computer, was not, Motionless Keyboard Co. v. Microsoft Corp., 486 F.3d 1376 (Fed. Cir. 2007).
Confirm the invention was ready for patenting when used: a working embodiment, or drawings and descriptions that would enable a skilled person to make it (Invitrogen; Minerva).
For third-party uses, confirm the use was open rather than secret. Note: An open third-party use counts against another inventor's patent, Baxter International, Inc. v. COBE Laboratories, Inc., 88 F.3d 1054 (Fed. Cir. 1996); a third party's secret commercial use does not (W.L. Gore). An accused infringer that was itself practicing in secret should look instead at the prior commercial use defense of 35 U.S.C. § 273.
Line up corroboration for every account of the use before relying on it (see Phase 12).

Phase 7: Experimental use (the patent owner's answer to Phases 6 and 8)

Identify who controlled the testing and the test units. Note: Control is important and sometimes dispositive. When the customer ran the tests to see whether a machine met its own needs, the inventor was not experimenting, Atlanta Attachment Co. v. Leggett & Platt, Inc., 516 F.3d 1361 (Fed. Cir. 2008). Prototypes handed to friends and acquaintances, with no monitoring, no records, and no secrecy, were in public use as a matter of law in Lough v. Brunswick Corp., 86 F.3d 1113 (Fed. Cir. 1996).
Confirm that the testing was aimed at the claimed features, or features inherent in them, rather than at durability for marketing, customer acceptance, or consumer preference. Note: See Electromotive Division of General Motors Corp. v. Transportation Systems Division of General Electric Co., 417 F.3d 1203 (Fed. Cir. 2005); Clock Spring, L.P. v. Wrapmaster, Inc., 560 F.3d 1317 (Fed. Cir. 2009) (a field demonstration to win industry acceptance was not experimentation); In re Smith, 714 F.2d 1127 (Fed. Cir. 1983) (consumer testing was market research).
Collect the objective evidence the courts weigh: test plans, data, reports, secrecy obligations, payment terms, number of units, duration, monitoring, whether the testing was systematic, and the nature of contacts with potential customers. Note: Those factors are catalogued in Allen Engineering Corp. v. Bartell Industries, Inc., 299 F.3d 1336 (Fed. Cir. 2002). For examples that succeeded, see TP Laboratories, Inc. v. Professional Positioners, Inc., 724 F.2d 965 (Fed. Cir. 1984) (an orthodontist's monitored use of his appliance on three patients, with no extra charge) and Manville Sales Corp. v. Paramount Systems, Inc., 917 F.2d 544 (Fed. Cir. 1990) (a new luminaire assembly for a highway light pole, installed at a rest area not yet open to the public to test it through a Wyoming winter).
Ask whether the invention had already been reduced to practice, because experimentation cannot negate a public use after that point, In re Omeprazole Patent Litigation, 536 F.3d 1361 (Fed. Cir. 2008), and whether the same evidence instead shows the invention was not yet ready for patenting, as in Barry v. Medtronic, Inc., 914 F.3d 1310 (Fed. Cir. 2019).
Read the contract before the testimony. Note: Calling a deal a "pilot," "evaluation," or "test" does not change commercial terms, Sunoco Partners Marketing & Terminals L.P. v. U.S. Venture, Inc., 32 F.4th 1161 (Fed. Cir. 2022), and a witness's conclusory testimony about what the company would have done could not override an unambiguous documentary record of an offer in Merck & Cie v. Watson Laboratories, Inc., 822 F.3d 1347 (Fed. Cir. 2016).

Phase 8: On sale

Find the first offer or sale for each product version, and date the offer rather than the delivery or the invoice. Note: A single offer is enough; no acceptance, delivery, or completed sale is required. The two-part test of Pfaff v. Wells Electronics, Inc., 525 U.S. 55 (1998) asks whether the invention was the subject of a commercial offer for sale and was ready for patenting.
Test the communication against general contract law: could the recipient have formed a binding contract simply by accepting it? Group One, Ltd. v. Hallmark Cards, Inc., 254 F.3d 1041 (Fed. Cir. 2001). Note: Advertisements, price lists, and quotations are usually invitations to negotiate rather than offers (Restatement (Second) of Contracts §§ 24 and 26), though they are evidence of commercial activity. Purchase orders, invoices, signed supply agreements, and online checkouts that take money for a defined product usually are offers or sales.
Confirm that what was offered embodied every claim element, expressly or inherently. Nobody needs to have recognized it at the time. Note: Sales of a drug substance that turned out, on later testing, to be the claimed crystal form barred the claim even though neither buyer nor seller knew which form they were trading, Abbott Laboratories v. Geneva Pharmaceuticals, Inc., 182 F.3d 1315 (Fed. Cir. 1999).
For method claims, look for offers to perform the method for a customer, Scaltech Inc. v. Retec/Tetra, LLC, 269 F.3d 1321 (Fed. Cir. 2001), or paid performance of it, Quest Integrity USA, LLC v. Cokebusters USA Inc., 924 F.3d 1220 (Fed. Cir. 2019). A license to practice a process is not, by itself, a sale of it, In re Kollar, 286 F.3d 1326 (Fed. Cir. 2002).
For the patent owner's own secret process, look for sales of products made with it. Note: Selling the product of a secret process puts the process on sale against the seller's later process patent, under the AIA as before it, Celanese International Corp. v. International Trade Commission, 111 F.4th 1338 (Fed. Cir. 2024); D.L. Auld Co. v. Chroma Graphics Corp., 714 F.2d 1144 (Fed. Cir. 1983).
Confirm the invention was ready for patenting when the offer was made: an actual reduction to practice, or drawings or descriptions specific enough to let a skilled person practice it (Pfaff).
Disregard confidentiality for this element. A sale under a nondisclosure agreement is still a sale, Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA, Inc., 586 U.S. 123 (2019).
Map the supply chain: who held title, what was being paid for, whether the supplier could sell to anyone else, and whether the goods went into the patent owner's stockpile or to the market. Note: A contract manufacturer's sale of manufacturing services, with title never passing to anyone but the patent owner, was not a commercial sale of the invention in The Medicines Co. v. Hospira, Inc., 827 F.3d 1363 (Fed. Cir. 2016) (en banc). But there is no general "supplier exception," Special Devices, Inc. v. OEA, Inc., 270 F.3d 1353 (Fed. Cir. 2001); Hamilton Beach Brands, Inc. v. Sunbeam Products, Inc., 726 F.3d 1370 (Fed. Cir. 2013), and no "joint development" exception, Brasseler, U.S.A. I, L.P. v. Stryker Sales Corp., 182 F.3d 888 (Fed. Cir. 1999).
Identify the seller, and do not assume a third party's sale is harmless to the patent owner. Note: Third-party sales count, and the courts have refused exceptions for sellers who acted innocently or even misappropriated the invention, Abbott; Evans Cooling Systems, Inc. v. General Motors Corp., 125 F.3d 1448 (Fed. Cir. 1997). Under the AIA, a disclosure by someone who obtained the subject matter from the inventor is excepted only within the year before the effective filing date. A third party's confidential sale is less settled: Helsinn involved the patent owner's own sale, and W.L. Gore protects inventors against third parties' secret uses, so build the record on how commercial and how public the transaction was.
Confirm the location of the offer for pre-AIA claims ("in this country"); the AIA has no geographic limit.
Before concluding, run Phase 7 (experimental use) and Phase 10 (the grace period) against the same transaction.

Phase 9: Otherwise available to the public (AIA only)

Use the AIA's catch-all for public disclosures that fit no other category: oral presentations, demonstrations, videos, store displays. Record what the audience could actually learn about each claim element (MPEP § 2152.02(e)). Note: Most such events are also public uses or printed publications, so the catch-all is usually a backstop. Helsinn held that it does not add a "public" requirement to the on-sale category.

Phase 10: Exceptions that take a reference out

AIA claims

Check § 102(b)(1)(A): was the disclosure made one year or less before the effective filing date by the inventor, a joint inventor, or someone who obtained the subject matter from them? Note: The vehicle in prosecution is an attribution declaration under 37 C.F.R. § 1.130(a). If the publication names co-authors who are not inventors, explain their role; a sworn explanation that co-authors were students working under the inventor's direction removed an article in In re Katz, 687 F.2d 450 (CCPA 1982), and MPEP § 2155.01 follows that approach.
Check § 102(b)(1)(B): did the inventor publicly disclose the same subject matter before a third party's intervening disclosure within the grace year? Note: The USPTO excepts only the subject matter the inventor actually disclosed, not anything the third party added (MPEP § 2153.02; 78 Fed. Reg. 11,059 (Feb. 14, 2013)). The inventor's earlier disclosure must really have been public: a private, non-confidential sale was not a public disclosure under the parallel provision in Sanho Corp. v. Kaijet Technology International Ltd., 108 F.4th 1376 (Fed. Cir. 2024). The prosecution vehicle is a declaration under 37 C.F.R. § 1.130(b) that attaches or describes the earlier disclosure.
For § 102(a)(2) art, check § 102(b)(2)(A) (obtained from the inventor) and § 102(b)(2)(B) (the inventor publicly disclosed the subject matter before the reference was effectively filed; Sanho again).
Check § 102(b)(2)(C): were the reference's subject matter and the claimed invention owned by, or subject to an obligation of assignment to, the same person not later than the claim's effective filing date? Check also the joint research agreement provision of § 102(c). Note: Common ownership removes only § 102(a)(2) art. Once the same application publishes and the grace year passes, it is § 102(a)(1) art against everyone, including its owner. For research collaborations, see the Joint Development Agreement Checklist.
Remember the limits: nothing in § 102(b)(1) removes a § 102(a)(1) disclosure made more than one year before the effective filing date (the § 102(b)(2) exceptions for earlier-filed applications have no such time limit, but they do not remove the same document as § 102(a)(1) art once it has published), and a Rule 130 declaration is not the tool when the real dispute is that another applicant claiming the same invention took it from your inventor; that belongs in a derivation proceeding under 35 U.S.C. § 135.

Pre-AIA claims

Check whether the patent owner can antedate a § 102(a) or § 102(e) reference under 37 C.F.R. § 1.131 (an actual reduction to practice before the reference date, or conception before it plus diligence to a reduction to practice) (MPEP § 715). Note: Antedating never works against a § 102(b) statutory bar. In litigation, the challenger keeps the burden of persuasion, but once it shows art predating the filing date the patent owner must come forward with corroborated evidence of an earlier invention date, Mahurkar v. C.R. Bard, Inc., 79 F.3d 1572 (Fed. Cir. 1996).
Check whether the reference describes the inventor's own work (the Katz showing), which removes it from § 102(a) and (e) but not from § 102(b).
Check pre-AIA § 103(c): common ownership or a joint research agreement removes § 102(e), (f), and (g) art for obviousness only, never for anticipation.

Phase 11: Content: can it anticipate, or only contribute?

Map every claim element, arranged as in the claim, to one reference, expressly or inherently, Verdegaal Bros., Inc. v. Union Oil Co. of California, 814 F.2d 628 (Fed. Cir. 1987). Note: Elements drawn from different embodiments of one reference are an obviousness argument unless the reference directs the combination, Net MoneyIN, Inc. v. VeriSign, Inc., 545 F.3d 1359 (Fed. Cir. 2008); a short list of options 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).
If you need a second document, check whether the first incorporates it by reference with detailed particularity, which makes it part of the single reference, Advanced Display Systems, Inc. v. Kent State University, 212 F.3d 1272 (Fed. Cir. 2000). Otherwise separate documents are separate references (Kyocera).
For any element that is not express, prove it is necessarily present, not merely probable, Continental Can Co. USA, Inc. v. Monsanto Co., 948 F.2d 1264 (Fed. Cir. 1991); contemporaneous recognition is not required, Schering Corp. v. Geneva Pharmaceuticals, Inc., 339 F.3d 1373 (Fed. Cir. 2003). Plan the expert testimony or test data that will show it.
Confirm the reference enables what it discloses. Prior art patents and publications are presumed enabling, subject to rebuttal by the patent owner, Amgen Inc. v. Hoechst Marion Roussel, Inc., 314 F.3d 1313 (Fed. Cir. 2003); In re Antor Media Corp., 689 F.3d 1282 (Fed. Cir. 2012). An anticipating reference need not show that the invention works or what it is for, In re Gleave, 560 F.3d 1331 (Fed. Cir. 2009).
For ranges, genera, and species, apply the specific rules: a prior species anticipates a later genus, and a point inside a claimed range anticipates the range, Titanium Metals Corp. of America v. Banner, 778 F.2d 775 (Fed. Cir. 1985); a prior genus anticipates a later species only if it is small enough to envisage each member, In re Petering, 301 F.2d 676 (CCPA 1962).
If any element is missing, plan the obviousness use now: the primary reference, what supplies the missing element, the reason to combine with a reasonable expectation of success under KSR International Co. v. Teleflex Inc., 550 U.S. 398 (2007), and the objective indicia the other side will raise under Graham v. John Deere Co., 383 U.S. 1 (1966). The response side is covered in Overcoming an Obviousness Rejection: A Practical Checklist.

Phase 12: Proof

Identify the burden in each forum. In district court and at the ITC, invalidity must be proved by clear and convincing evidence, whether or not the examiner saw the art, Microsoft Corp. v. i4i Ltd. Partnership, 564 U.S. 91 (2011). In inter partes and post-grant review the standard is a preponderance (35 U.S.C. § 316(e); 35 U.S.C. § 326(e)), and at institution the Board asks whether there is a reasonable likelihood that a reference was publicly accessible, on the totality of the evidence (Hulu, LLC v. Sound View Innovations, LLC, IPR2018-01039, Paper 29 (PTAB Dec. 20, 2019) (precedential)).
Authenticate every document through a witness with knowledge, distinctive characteristics, comparison, or the ancient-documents provision (Rule 901), or by self-authentication, including certified business records under Rule 902(11).
Use declarations under 28 U.S.C. § 1746 for librarians, archivists, records custodians, and fact witnesses, and confirm each witness can be produced for deposition or cross-examination.
Corroborate every witness whose testimony is offered to prove a prior use, sale, or publication. Note: The skepticism is old, The Barbed Wire Patent, 143 U.S. 275 (1892), and the rule applies to interested and disinterested witnesses alike, Woodland Trust v. Flowertree Nursery, Inc., 148 F.3d 1368 (Fed. Cir. 1998); Finnigan Corp. v. International Trade Commission, 180 F.3d 1354 (Fed. Cir. 1999). Contemporaneous documents are the best corroboration, Juicy Whip, Inc. v. Orange Bang, Inc., 292 F.3d 728 (Fed. Cir. 2002), judged under a rule of reason, Sandt Technology, Ltd. v. Resco Metal & Plastics Corp., 264 F.3d 1344 (Fed. Cir. 2001). Paid consultants recalling a trade show handout from years earlier created a credibility question for the jury in TypeRight Keyboard Corp. v. Microsoft Corp., 374 F.3d 1151 (Fed. Cir. 2004).
For physical products, document provenance (date codes, invoices, shipping records), configuration (firmware versions, part numbers, service history), and a chain of custody from acquisition through teardown; keep the units.
Preserve your own evidence and send preservation demands to third parties early; see the Litigation Hold and Evidence Preservation Checklist: A Practical Checklist.
Budget lead time for evidence abroad (Hague Convention requests take months) and for witnesses outside subpoena range under Fed. R. Civ. P. 45(c).

Phase 13: Forum and timing

For an inter partes review, confirm the ground is § 102 or § 103 based only on patents and printed publications, 35 U.S.C. § 311(b), and that the petition will be filed within one year after service of an infringement complaint, 35 U.S.C. § 315(b). Note: Estoppel under § 315(e)(2) reaches grounds the petitioner raised or reasonably could have raised, measured by what a skilled searcher's diligent search would have found, with the burden on the patent owner, Ironburg Inventions Ltd. v. Valve Corp., 64 F.4th 1274 (Fed. Cir. 2023). It does not reach public use, on-sale, or prior-knowledge grounds, even when printed materials help prove them, Ingenico Inc. v. IOENGINE, LLC, 136 F.4th 1354 (Fed. Cir. 2025). See PTAB Post-Grant Checklist: A Practical Checklist.
For a post-grant review, confirm the patent is an AIA patent and the petition can be filed within nine months after grant; any invalidity ground is available, including public use and on sale, 35 U.S.C. § 321.
For ex parte reexamination, confirm the art is patents or printed publications, 35 U.S.C. § 302.
In district court, calendar the invalidity contentions under the local patent rules, amend promptly when new art is found (good cause requires diligence, O2 Micro International Ltd. v. Monolithic Power Systems, Inc., 467 F.3d 1355 (Fed. Cir. 2006)), and serve the written notice required by 35 U.S.C. § 282(c) at least 30 days before trial, including the name and address of every person relied on for prior knowledge, use, or offers for sale. Invalidity must also be pleaded; see the Answer and Affirmative Defenses Checklist: A Practical Checklist.
In prosecution, cite material art under the duty of disclosure in 37 C.F.R. § 1.56 with an information disclosure statement that meets the timing rules of 37 C.F.R. § 1.97 and the content rules of 37 C.F.R. § 1.98 (MPEP § 609). Third parties can submit printed publications in a pending application under 35 U.S.C. § 122(e) within the statutory window, and anyone can cite patents and printed publications in an issued patent's file under 35 U.S.C. § 301.

Phase 14: For patent owners: run the checklist in reverse

Every element the challenger must prove is a place to push. Work through these before the invalidity contentions arrive, not after.

Attack the date. Separate the printed date from the accessibility date; demand the capture of the file, not just the page that linked to it; check for print-on-demand stamps (VidStream); and test the priority claim of any § 102(a)(2) reference passage by passage.
Attack the publicness. Who could have found the document, and how? Look for absent indexing, a tiny or closed audience, and confidentiality norms (Blue Calypso; Acceleration Bay; Cordis). For uses, build the record of control and implied confidentiality (Moleculon; American Seating).
Attack the embodiment. Prove that the version shown, used, or sold before the critical date lacked a claim element: earlier firmware, a different latch, a part added later. Configuration records and engineering change orders are the evidence.
Attack the proof. Object to unauthenticated captures and undated documents, insist on corroboration for every witness, probe the chain of custody of physical exhibits, and expose any witness's financial interest (TypeRight).
Raise the exceptions with documents. The grace period, a Rule 130 showing, common ownership, and experimental use all need contemporaneous records; testimony alone rarely carries them (Merck & Cie).
Defend the priority date. Prepare a support chart showing where the earliest application describes every element of every asserted claim, because you will have to come forward with it (Technology Licensing; PowerOasis).
Hold the challenger to its disclosures. Theories missing from the contentions or the § 282(c) notice may be excluded (O2 Micro), and a petitioner that took an IPR to a final written decision is estopped on the patent and printed publication grounds it raised or reasonably could have raised (Ironburg).
Audit your own history before you sue. An on-sale or public use problem that the defendant finds in your files after you file suit becomes an argument for fees under 35 U.S.C. § 285.

Phase 15: For inventors before filing: the self-audit

Build a disclosure calendar listing every talk, poster, paper, demonstration, beta program, quote, purchase order, crowdfunding or preorder page, app store listing, manual, regulatory filing, and investor deck sent without a nondisclosure agreement.
Identify the earliest public event. In the United States, the grace period ends one year after it; in most other countries, novelty for whatever was disclosed ended that day. See the International Patent Filing Checklist: A Practical Checklist.
File before the next disclosure, with a provisional under 35 U.S.C. § 111(b) that describes everything you are about to show; a thin provisional protects only what it describes (New Railhead).
Put NDAs in place before demonstrations, keep control of prototypes, and do not operate a working device for the trade before filing (Minerva; Motionless Keyboard). For drafting, see Drafting Enforceable Non-Disclosure Agreements for Technology Transactions.
Write beta and pilot agreements as experiments: a test plan tied to the claimed features, inventor control, records, confidentiality, no charge beyond cost, an end date, and return of the units (Allen Engineering; Sunoco).
Structure contract manufacturing as a purchase of services, keep title, deny the manufacturer any right to sell to others, and avoid commercial-quantity orders before filing (Medicines Co.; Hamilton Beach).
For processes, choose between patent and trade secret early. Selling product made by a secret process starts the clock (Celanese), and a documented secret commercial use may support a defense under § 273 against someone else's later patent.
Tell your patent attorney about every event on the calendar and disclose the material ones to the examiner; see Preparing an Invention Disclosure: A Practical Checklist and Maintaining the Duty of Candor to Avoid Inequitable Conduct: A Practical Checklist.

The qualification record

Complete one record per reference. It is short on purpose: if a line cannot be filled in with a source, the reference is not ready to rely on.

PRIOR ART QUALIFICATION RECORD                 Ref. ID: [  ]  Prepared: [DATE] by [NAME]
Patent / claims: [ ]          Statute: [AIA / pre-AIA]   Effective filing date(s): [ ]
Critical dates: EFD [ ]   EFD minus one year [ ]   Pre-AIA 102(b) date / invention date [ ]
Reference: [title, author or owner, version]       Found by / where: [ ]
Categories: [patent / publication / public use / on sale / other public / 102(a)(2) / pre-AIA]
Whose activity: [inventor / derived from inventor / third party]
Date relied on: [ ]     Proof of date: [catalog record, capture timestamp, invoice, witness]
Public accessibility or public/commercial character: [facts + source]
Confidentiality facts: [NDA, norms, control, none]      Ready for patenting: [how shown]
Exceptions checked: 102(b)(1)(A) [ ] (b)(1)(B) [ ] (b)(2)(A)-(C) [ ] experimental use [ ]
Content: anticipates claims [ ] / supports obviousness of claims [ ]   Inherency issues: [ ]
Enablement concerns: [ ]       Construction dependence: [term, both readings]
Authentication route: [ ]      Hearsay route for date: [ ]     Corroboration: [documents]
Witnesses (name, address, availability): [ ]                    Physical evidence held by: [ ]
Forums: IPR [Y/N]  PGR [Y/N]  district court/ITC [Y/N]  Reexam [Y/N]
Open items and owners: [ ]

Frequently asked questions

Does a reference have to be in English or come from the United States? No, not under the AIA: patents, publications, uses, and sales anywhere in the world count. Pre-AIA law limited public uses and sales to the United States. A foreign-language reference you rely on needs an accurate translation; at the Board, 37 C.F.R. § 42.63(b) requires a translation and an affidavit attesting to its accuracy.

Is a page on the Wayback Machine automatically prior art? No. A capture shows that a page existed at a public address on a date. You still need to authenticate the capture, prove that the specific file you rely on was captured before the critical date, and show that an interested person could have found it.

Can our own brochure, demo video, or conference talk be used against our patent? Yes. Your own disclosures are prior art like anyone else's once they are more than one year before the effective filing date. Inside that year they are excepted in the United States, but in most other countries they still destroy novelty. Nobel Biocare involved the inventor's own company's catalog.

Can a confidential sale be prior art? A patent owner's own sale counts even if it was confidential (Helsinn). Whether a third party's confidential sale counts against an unrelated inventor is less settled; build the record on how commercial and how public the transaction was.

Do we have to prove that someone actually read the article? No. Public accessibility is enough; actual readership is not required (Constant; Samsung).

Can we use a product in an inter partes review? Not as such. The Board hears only patents and printed publications, but a manual, brochure, or catalog that describes the product may qualify as a printed publication (Weber; GoPro), and the product itself remains available in court even after an unsuccessful IPR (Ingenico).

What if the only evidence of a prior use is a witness's memory? Then you do not yet have prior art. Find the documents that corroborate the story (invoices, photographs, date books, emails, shipping records) before you build a theory on it (Woodland Trust; Finnigan).

Practical takeaways

Date every claim before you date any reference; a lost priority claim can turn the patent owner's own launch into the best prior art in the case.
Classify each reference into every category it fits, because the categories have different proof and different forums.
For documents, prove public accessibility and the date it began, not just the date printed on the page.
For uses, prove the absence of confidentiality and readiness for patenting; for sales, prove a contract-law offer of something that embodied the claim, secret or not.
Run the exceptions and experimental use before you rely on the patent owner's own activity, and read the contract before the testimony.
Corroborate every witness, authenticate every capture, and keep every physical exhibit.
Match the art to the forum: paper to the Board, products and transactions to court, the ITC, or post-grant review.

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