In a recent precedential opinion, the United States Court of Appeals for the Federal Circuit affirmed that a patent application constitutes prior art as of its filing date, not its publication date.

In Lynk Labs. Inc. v. Samsung Electronics Co., Ltd., Lynk Labs sued Samsung for infringement of a single patent relating to LED technology. Samsung responded by initiating an inter partes review at the Patent Trial and Appeal Board to invalidate the asserted patent. A central question was whether a patent application that published only after the priority date of the Lynk Labs patent could be considered prior art.

In deciding this issue, the Federal Circuit acknowledged that most printed references — for example manuscripts, books and product brochures — do not constitute prior art until they are publicly accessible. However, Congress created a specific exception for patent applications at Section 102(a)(2) of the Patent Act. As noted by the Federal Circuit, Congress specifically determined that a published patent application is prior art as of its earliest effective filing date. Thus, a patent application can constitute prior art against a patent if the patent application was (a) filed before the priority date of the patent and (b) ultimately published, regardless of when.

The use of so-called “secret prior art” is permitted under these narrow circumstances, even though the prior art was not publicly accessible at the time of its filing. Because Samsung’s patent application constituted prior art, the Federal Circuit affirmed the decision of the Patent Trial and Appeal Board to invalidate all challenged claims of the Lynk Labs patent.

This decision of the Federal Circuit highlights the importance of promptly filing patent applications to secure an early priority date. For parties seeking to invalidate a competitor’s patent, the decision also underscores the need for thorough prior art searches that consider not only publication dates but also the earliest effective filing date of available prior art.