Prior Art: The Concept That Can Kill Any Patent

Every patent granted by the USPTO comes with an implicit promise: this invention was new at the time of filing. Prior art is everything that proves it wasn't.

The definition

Prior art includes anything publicly available before the patent's "priority date" that describes the invention being claimed. This can be:

• Earlier patents, anywhere in the world
• Scientific papers and journal articles
• Products that were publicly sold or offered for sale
• Public demonstrations, trade show presentations
• Even a dated lab notebook, under certain conditions

If your claimed invention is already described in prior art, the patent should never have been granted. If it slipped through — which happens — the patent is vulnerable to invalidity challenges.

How prior art kills patents

There are two ways prior art defeats a patent claim:

Anticipation (§102): A single prior art reference discloses every element of the claim. It's the nuclear option — one document, one claim, patent dead.

Obviousness (§103): No single reference discloses everything, but combining two or more makes the invention obvious to someone skilled in the field. This is the more common challenge and the harder one to adjudicate — "obvious" is subjective enough that it generates enormous litigation.

The prior art search problem

Patent examiners get roughly 20 hours to search for prior art before deciding on an application. That's not much time to scour all of human knowledge. Academic literature is systematically undersearched. Products that were sold but never documented are nearly impossible to find.

This is why patents get granted that probably shouldn't be. And it's why post-grant challenges — Inter Partes Review (IPR) and Post-Grant Review (PGR) at the Patent Trial and Appeal Board — were created. They give a mechanism for challenging granted patents with newly found prior art.

Prior art as a business strategy

Tech companies don't just defend against patent attacks. They proactively build prior art to defend future freedom to operate.

Google's Patent Library, IBM's "Defensive Publication" program, the Open Invention Network — these exist specifically to create published prior art that preempts future patent applications. If you publish a description of a technique before anyone patents it, you haven't gotten a patent, but you've prevented anyone else from getting one either.

This is the defensive publication strategy: sacrifice patent protection in exchange for ensuring no one else can use patents to lock down the technology.

Searching prior art yourself

USPTO's Patent Full-Text Database, Google Patents, and Espacenet (for international patents) are free. A good prior art search for a specific claim element takes 30–60 minutes if you know what you're looking for.

The trick is thinking like the patent — searching for the functional description of what the claimed element does, not just the specific terminology the patent uses. Patents frequently use novel terminology for ordinary concepts. The prior art uses the ordinary concepts.