35 U.S.C. § 102 is the simplest of the patent invalidity grounds and often the most powerful. The rule, in plain language: if the invention was already public — anywhere, in any form — before the patentee filed, the patent is invalid for lack of novelty.
Most invalidity defenses end up turning on prior art. Knowing what counts as prior art and how to find it is the foundation of patent defense.
What counts as prior art
Under the post-AIA (2013-onward) version of § 102, prior art includes anything that, before the effective filing date of the patent:
- Was patented (anywhere in the world).
- Was described in a printed publication (anywhere, in any language).
- Was in public use (in the US, post-AIA, anywhere).
- Was on sale (offered or actually sold).
- Was otherwise available to the public — websites, conference talks, product manuals, online forums, GitHub repos.
Two important things follow:
- Geographic scope is global. A 1987 Japanese-language paper anticipates a US patent if it discloses the invention.
- Format is open. A YouTube demo, a forum post, a product manual, an internship presentation — all qualify if dated before the filing date and substantive enough to enable a person of ordinary skill to practice the invention.
The on-sale and public-use bars
Pre-AIA, the on-sale bar and public-use bar were technically distinct, with grace periods. Post-AIA, the rules are tighter:
- If the invention was on sale or in public use before the filing date, the patent is invalid — even if the inventor is the one who put it on sale.
- One narrow safe harbor: a one-year grace period for disclosures by the inventor or someone who got the information from the inventor.
Translation: a startup that demos a product at a trade show in 2024 has until 2025 to file. After that, the trade-show demo is prior art against their own application.
This bar bites a lot of inventors who didn't realize their own activities counted.
Anticipation: the § 102 standard
For a single piece of prior art to anticipate a claim under § 102, it must disclose every limitation of the claim, arranged or combined as in the claim.
Three traps:
- Single reference rule. § 102 anticipation requires one reference. Combining two references is § 103 obviousness, governed by KSR v. Teleflex, not § 102.
- Inherency. A reference can anticipate even if it doesn't explicitly mention a limitation, if that limitation is necessarily present. Often litigated.
- Enablement. The prior-art reference must enable a person of ordinary skill in the art to practice the claim. A vague mention of a concept doesn't anticipate; a working description does.
Where to look for prior art
A serious prior-art search uses multiple sources:
- Patent databases. Google Patents, USPTO Patent Public Search, Espacenet (EPO), J-PlatPat (JPO). Free.
- Non-patent literature. IEEE Xplore, ACM Digital Library, Google Scholar, arXiv. Some require subscription.
- Standards bodies. IEEE, ISO, IETF (RFCs), ITU. Many standards predate corresponding patents.
- Product manuals and datasheets. Older versions live on Archive.org or vendor archives.
- Web archives. The Wayback Machine. Crucial for software patents where the alleged invention has obvious online precursors.
- Company technical blogs and conference talks. Date-stamped writeups, often missed by examiners who searched only patent databases.
- Forum posts. Slashdot, Stack Exchange, and similar can be dated and substantive.
Hour for hour, the Wayback Machine is one of the highest-yield resources for software patents — pre-filing screenshots of competing products often disclose the patentee's "novel" feature.
Date analysis
For each candidate prior-art reference, you need:
- A reliable date earlier than the patent's effective filing date. Filing date → priority date if the patent claims benefit of an earlier application.
- Public availability as of that date. A draft on a private hard drive doesn't count; a paper at a conference does.
- Disclosure of every limitation. Run a claim chart.
Date proof is often the weak link. A printed publication needs proof of date and circulation. A web page needs Wayback Machine confirmation. Internal company documents may need testimony.
How § 102 plays in litigation and IPR
District court. § 102 invalidity must be proved by clear and convincing evidence because issued patents enjoy a presumption of validity. This is harder than it sounds — even strong prior art can be argued around.
IPR (Inter Partes Review). § 102 is one of the two grounds available (along with § 103). The standard drops to preponderance of the evidence. This is the main reason IPRs invalidate patents at the high rates they do.
Building a § 102 case
The basic playbook:
- Identify the priority date. Most patents claim priority back to an earlier application. Get the earliest date.
- Search broadly. Use multiple databases. Don't stop at the first hit.
- Date-verify each candidate. Get a citation, a circulation date, an Archive.org capture.
- Build a claim chart. For each candidate, map each claim limitation to specific text in the reference.
- Pick the strongest one or two. A § 102 case usually rises or falls on a single great reference.
- Have a § 103 backup. If § 102 fails because one limitation is missing, the obviousness combination of two references with motivation to combine often works.
Bottom line
Most issued patents have anticipating prior art that the examiner missed. The work is finding it and proving the date. For software patents, web archives are gold. For hardware, conference proceedings and standards documents. For pharma, journal articles. The defense isn't always hard — but it's always work. (See a worked § 102 analysis on the Lumen View patent.)
This article is for general education and is not legal advice.