Can a secret patent be used as prior art under 35 U.S.C. 102(a) or pre-AIA 35 U.S.C. 102(a) or (b)?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

No, a secret patent cannot be used as prior art under 35 U.S.C. 102(a) or pre-AIA 35 U.S.C. 102(a) or (b). The MPEP 2126 states:

“Even if a patent grants an exclusionary right (is enforceable), it is not available as prior art under 35 U.S.C. 102(a) or pre-AIA 35 U.S.C. 102(a) or (b) if it is secret or private.”

This principle was established in the case of In re Carlson, where the court held that a document must be at least minimally available to the public to constitute prior art. Secret patents are defined as patents that are insufficiently accessible to the public to qualify as “printed publications.”