What is Prior Art?

The term "prior art" is used in the patent field to mean any information that is relevant to determining patentability and scope of a claim. Since the focus is on individual claims, the prior art necessarily differs from patent to patent, and even from claim to claim.

In the United States prior art is defined by 35 USC § 102. This is a labyrinthine piece of writing even by government standards, and is impossible to understand without guidance on what is meant by "printed publications," "on sale", "public use", "the invention", "in this country", and various other terms used in that section. Fortunately, the Patent Office devotes the entirety of MPEP Chapter 2600 to the topic.

The most critical determination of whether an item (sometimes called a "reference" in patent law) is or is not prior art hinges upon the date of the item. Prior art is limited to items that fall within any of the following categories:

Before the invention by the applicant:

• Evidence that the invention was known or used by others in this country (§ 102(a));
• Evidence that the invention was invented by another, diligently prosecuted in a patent application, and not abandoned, suppressed, or concealed (§ 102(g)(1),(2));
• Printed publication in the U.S. or abroad (§ 102(a)); or
• Patent application filed by another in the United States, or filed through the PCT if published in English (§ 102(e)(1),(2))

More than one year before the applicant filed for a patent in the U.S.:

• Evidence that a product containing the invention was offered for sale, or on sale (§ 102(b));
• Issued patent in the U.S. or abroad (§ 102(b), (d)); or
• Printed publication in the U.S. or abroad (§ 102(b))

Before the applicant filed for a patent in the United States:

• Issued patent or inventor's certificate abroad, but only if the application for same was filed more than 12 months before the (§ 102(d))

Assuming that the inventor filed his/her patent application within a year of making the invention, this all boils down to finding printed publications (whether issued patents, patent publications, invoices, shipping documents, offers for sale, or any other documents) that are made publicly accessible more than a year before the filing date of the patent application.

Of course where the patent application is a child of an earlier filed application, then the "application date" of the child is taken to be the filing date of the parent. That earlier date is often referred to as the "priority date" of the child application. For CIP applications, in which additional matter was added in the child application, there are two priority dates; an earlier date for the subject matter disclosed in the parent application, and a later date for the newly added subject matter.

Inventors sometimes think that U.S. patents are only considered prior art as of their issue date. That contention used to be valid, but the situation changed several years ago. U.S. published patent applications and issued patents are given 102(e) prior art effect as of the filing date of the application. PCT applications filed in English after 11/29/00 are also given prior art effect as of the filing date of the application. A patent issued on a PCT application not published in English is given no Section 102(e) prior art effect at all.

One often needs to resolve whether or not information constitutes a printed publication. For example, is a Ph.D. thesis in a major university considered a printed publication for purposes of 35 USC § 102(b)? What about a mere term paper? Actually, the distinction has nothing to do with the sophistication of the publication or the context in which it was created, but instead has everything to do with whether the document was "publicly accessible". A reference is "publicly accessible" whenever:

"… persons interested and ordinarily skilled in the subject matter . . . exercising reasonable diligence, can locate it and recognize and comprehend therefrom the essentials of the claimed invention without need of further research or experimentation"

Several cases have required that publication allows those interested in the art a sufficient amount of time to "capture, process and retain the information conveyed by the reference", or to locate the material "in a meaningful way". But those tests are fairly easy to satisfy because they merely address technical accessibility. In Bruckelmyer v. Ground Heaters, Inc. , for example, the Federal Circuit found that canceled drawing figures in a Canadian patent application were publicly accessible even though neither the figures nor even the application had been specifically indexed, and there were no copies known to have been made or sent outside the Canadian patent office during the prior art period. In that instance the figures were considered to be § 102(b) prior art merely because the Canadian prosecution file had technically been open to the public more than a year before the inventor filed his U.S. application. The bottom line is that, at least during the searching process, one should assume that any relevant documents that the searcher can find will be considered publicly accessible.