Under U.S. patent law, an invention claimed in a U.S. patent application filed prior to November 29, 2000, which has not been voluntarily published by the USPTO lacks novelty if it was described in a U.S. patent granted on a "parent" PCT application by another who filed a "child" national application in the U.S. prior to the date it was invented by the applicant for a patent [35 U.S.C. 102(e)]. This a more special case of the 35 U.S.C. 102(e) special case in which the PCT route to filing a U.S. patent application has been used.
The general rule of 35 U.S.C. 102(e) is a special case in that the document (called a "reference") that destroys novelty becomes effective (has an "effective date" that occurs) when the reference is still unpublished (because U.S. applications are not published). The parent PCT application may or may not have been published (but usually is) before the child U.S. national application that is used as the reference) is filed. If the applications are both assigned to the same entity or if there is any overlap in inventorship (there is at least one common inventor who is listed in both U.S. applications), the issue can even arise before the earlier-filed U.S. application issues.
This rule requires that the national stage of a PCT application that has designated the U.S. to have been "commenced" by the depositing (filing) in the USPTO of three items. Those three items are: (1) the national patent application fee, (2) a copy of the international application and a translation of the application into the English language, if it was filed in another language and (3) an oath or declaration by the inventor(s). Only after these three items have been deposited in the USPTO is the national U.S. application that is being used as the reference effective for the purposes of 35 U.S.C. 102(e). Thus, the filing date of the PCT application is not the filing date of the reference used in this rule.
It should be noted, however, that there is a very special case of this more special case. A U.S. national application (filed prior to November 29, 2000, which has not been voluntarily published by the USPTO) that is patented "via the PCT route" can claim the benefit of the filing date of an earlier-filed, related U.S. or international application designating the U.S. in the same way that a regular U.S. patent application can (35 U.S.C 120) if it is filed as a continuation, continuation-in-part or divisional application. The later-filed application must include an appropriate reference to the earlier-filed application, be copending with that application and have at least one inventor in common with that application. In this very special case, then, the effective filing date of a U.S. patent reference (derived from an national application that is a continuation of a PCT application) can be used as the effective date of the reference under 35 U.S.C. 102(e).
Only issued U.S. patents and issued Statutory Invention Registrations can destroy novelty under this rule; issued non-U.S. (foreign) patents cannot. However, as was noted above, if there is common owership or inventorship, maintaining the secrecy of the earlier-filed application is not an issue, and a "provisional" rejection of the later-filed application can be made under 35 U.S.C. 102(e). Anything that could have been claimed in the reference can be relied on by the Examiner to reject the claimed invention.
Because an applicant(s)'s filing date is initially presumed to be his/her/their date of invention, a rejection under 35 U.S.C. 102(e) may be overcome by proving a date of invention earlier than the effective date of the reference. However, the date of invention can only be carried back one year before the earliest U.S. filing date, which can be the PCT filing date. A rejection under 35 U.S.C. 102(e) may also be overcome by proving that the invention described in the reference was not invented by "another," i.e., that the invention was invented by the same inventive entity as the current applicant(s).