It is well settled that an issued U.S. patent is available to be cited as prior art as of “the filing date of the earliest U.S. application to which the patent is entitled.” What if the said patent application claimed the benefit of an earlier filed provisional patent application? Is the issued patent available as a prior art reference as of the filing date of the provisional application?
Surprisingly, this question has not been previously addressed by a court. Well, now the C.A.F.C. has decided the matter. (In re Giacomini)
Not wishing to keep the reader in suspense any longer, we can report that the C.A.F.C. affirmed the position taken by the Patent Office, namely that “a U.S. patent or published application will be considered prior art as of the filing date of its qualifying provisional application.”
The ruling makes sense. Indeed, it's pretty unbelievable that no court had ever addressed the issue before.