Confusion Over the Prior Art Date of United States Patents Issued from PCT Applications

I.     Introduction

Question: What would be the effect on a company’s patent portfolio if the prior art date of thousands of United States patents suddenly changed by approximately 30 months? The answer is that many of the company’s United States patents might be invalid or defective. Believe it or not, there is such a class of United States patents: The United States patents granted on PCT (Patent Cooperation Treaty) applications. This paper explains why that may be case and provides advice on actions that a company may take to limit the damage if that is the case.

II.    Why PCT Patents May be Defective

During the negotiations that led up to the PCT, the United States held out for the reservation embodied in PCT Article 64(4)(a). That reservation allowed the United States to preserve the famous holding in In re Hilmer,1 that patent applications filed outside of the United States are not prior art — even when they are identified as the Paris Convention priority application supporting a later filed United States patent application. Article 64(4)(a) in the PCT allows the PCT States to reserve the right to exclude PCT applications filed outside of that State (as of their PCT filing date) from what is considered prior art by the national laws of that State. The United States’s reservation under PCT Article 64 (4)(a) states that “the filing outside of the United States of an international application designating this country is not equated to an actual filing in the United States for prior art purposes.”2 The national laws of the United States were amended to implement the PCT.3 However, the United States laws implementing its PCT Article 64(4)(a) reservation are less than clear.4 Based upon those laws, the prior art date of a United States patent granted on an international application can be construed to be either (1) the PCT international application’s actual filing date in the United States or (2) the date on which the PCT applicant completes the United States national stage filing requirements (including the filing in the United States Patent and Trademark Office of an English language copy of the specification of the invention, the United States national filing fee, and the executed inventor’s declaration of invention). To make matters worse, the United States national laws are silent on the prior art date of a patent issuing from an application claiming priority to a PCT application (i.e., a continuation of the PCT application). Typically, when the first application for an invention is “filed PCT,” the national stage requirements (in each country where protection is pursued) are not completed for another thirty months. This is because the PCT mandates that a State cannot require the applicant to enter that State’s national stage for thirty months.5 In fact, that ability to delay national stage fees and the associated attorneys fees in multiple countries while preserving the right to claim priority to the first filing date is the primary advantage of the PCT.

After the United States acceded to the PCT, the Commissioner of Patents opined that the United States national laws meant (1) that the prior art date of a patent maturing from a PCT application was the date that that application completed the national stage requirements and (2) that the prior art date of a patent granted on a continuation of a PCT application was the PCT application’s international filing date.6 Unfortunately, the Commissioner’s opinions do not distinguish PCT applications filed inside the United States from PCT applications filed outside the United States. The Commissioner’s opinions advise (and are followed by) the patent examiner corps on the prior art date of patents granted on PCT applications. The Commissioner also publishes on the face of patents granted on PCT applications what he believed to be their prior art date. The Commissioner’s actions result in the patent examiners (1) excluding, in their examination of applications, certain patents granted on PCT applications that may be prior art to the application under examination and (2) including, as prior art in their examination of applications, certain patents granted on PCT applications that may not be prior art to the application under examination. The Commissioner’s published prior art date of PCT patents has not, until recently, been challenged by the patent bar.

The Commissioner’s opinions were formed early on in the life of the PCT at a time when there were only a trickle of PCT applications filed in the United States Patent and Trademark Office. The Commissioner’s opinions were of little consequence at that time. However, globalization, including NAFTA, the Uruguay round of GATT, and the implementation of United States provisional applications7 has opened the PCT flood gates. Approximately two thousand PCT applications are being filed each month in the United States Patent and Trademark Office.8 Both of the Commissioner’s opinions are under unofficial reconsideration in the United States Patent and Trademark Office. In addition, there are some petitions to the Commissioner pending in the United States Patent and Trademark Office that, in effect, challenge the Commissioner’s opinions.9

Probably because of the examiner’s and the patent bar’s reliance upon the Commissioner’s opinions and actions, there is no judicial opinion in the United States providing guidance on the prior art date of a patent granted on a PCT application. However, it is clear that the Commissioner’s opinions run contrary to the United States’ intent in acceding to the PCT, to long established patent policies of the United States, and to judicial precedent existing prior to the PCT.10

The United States judicial opinions commenting on the meaning of prior art and expressing the United States’s policies on the meaning of prior art in addition to the intent expressed by the United States in acceding to the PCT all draw a clear distinction between the prior art effect of inventive acts occurring inside versus outside the United States. Inventive acts occurring inside the United States are accorded prior art effect.11 Inventive acts occurring outside the United States are not accorded prior art effect.12 Therefore, it is possible (1) that the prior art date of a patent granted on a PCT application filed inside the United States (i.e., in the United States Patent and Trademark Office), is its filing date, and that possibility is contrary to the Commissioner’s opinion. It is also possible that a patent granted on a continuation of a PCT application filed outside the United States is not prior art on the PCT application’s filing date, but is prior art on the (typically much later) date that that PCT application satisfies the United States national stage requirements, and that possibility is also contrary to the Commissioner’s opinion. If the Commissioner’s opinions are eventually found to be incorrect, then (1) most United States patents granted on PCT applications filed inside the United States are prior art as of their filing date, which is roughly 30 months earlier than the 35 US 102(e) prior art date printed on the face of those patents and (2) most United States patents granted on United States continuation applications claiming priority to a PCT application filed outside the United States are prior art roughly 18 months after the 35 USC 102(e) date printed on the face of those patents.13

Although the propriety of the Commissioner’s opinions are now at issue in the United States Patent and Trademark Office, it will probably be several years before those issues are finally decided by the United States Courts. In this sea of uncertainty, what actions should be taken to protect a company’s patent rights? There are both retrospective and prospective actions that may be taken.

III.    Actions That May Be Taken

Retrospective actions relate to issued United States patents. Companies’s should review their own patent portfolio of recently issued United States patents. Assume the company finds that the claims in one of its patents were narrowed in order to overcome a prior art rejection, and (1) that the rejection was based upon a United States patent, (2) that the United States patent was granted from a continuation of a PCT application, (3) that the PCT application was filed outside the United States, and (4) that the United States’s national stage filing requirements in the PCT application were completed subsequent to the company’s patent’s date of invention. Under those circumstances, the company should consider filing a reissue application for that defective patent in order to obtain broader protection. Alternatively, if there is a continuation application pending that claims priority to the defective patent, the continuation application may be used to obtain the desired scope of protection.

On the other hand, assume that claims in the company’s patent may be invalid over PCT based prior art. In that situation, a reissue application or request for reexamination may be filed in the hopes of strengthening the presumption of validity of that patent.

Furthermore, each company may consider the effect of a sea change in PCT prior art on its competitor’s patent portfolios. A third party reexamination request can be filed in the United States Patent and Trademark Office to “knock out” a competitors’ potentially invalid patent. Also note that a competitor may also be able to obtain broader protection via a reissue of one of their existing patents.

Opinions concerning validity over prior art and infringement may be affected by PCT prior art patents that either were not considered to be prior art or by PCT patents that were considered to be prior art but that in fact may not be prior art.14

Prospective actions relate to future patenting activities. First, all pending applications should be reviewed to ensure that claims have not been narrowed based upon PCT patents that may not be prior art.

For inventive activities occur in the United States, it may be more favorable to file a PCT application in the United States instead of a (non-provisional) patent application. Since the PCT application may provide all of the rights of a regular (non-provisional) patent application, and since the PCT application also preserves the right of priority for foreign filing for up to thirty months, it may be more favorable to file only a PCT application for any invention worthy of international protection.

If inventive activities occur outside the United States, it is more favorable to file a provisional application as soon as possible, in addition to filing either a foreign national or foreign PCT application. This is at least because the United States provisional application provides a filing “in the United States.” Perhaps the greatest benefit of the United States provisional application, which is often overlooked by foreign applicants, is that the provisional application enables the applicants the right to antedate references available up to one year prior to the filing date of the provisional application.15 That right is not provided by a foreign national application.16

Finally, it is likely that provisional applications will provide a prior art effect from their filing date. This is because (1) provisional applications are filed in the United States Patent and Trademark Office and (2) it appears to have been the intent of Congress that provisional applications have prior art effect from their filing date.17 However, no court has, as yet, opined on the prior art effect of a provisional application.


1.  359 F.2d 859, 149 USPQ 480 (CCPA 1966) (Rich, J.).
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2.  United States Instrument of Ratification of the PCT signed by President Nixon in 1974.
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3.  Treaties are not self implementing in the United States. They need to be implemented by laws passed by the Congress and signed into law by the President.
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4.  35 USC 363 and 35 USC 102(e) relate to the United States’s reservation under Article 64(4)(a) of the PCT. Those statutes state that:
35 USC 363:
International application designating the United States: Effect

An International application designating the United States shall have the effect, from its international filing date under article 11 of the treaty, of a national application for patent regularly filed in the Patent and Trademark Office except as otherwise provided in section 102(e) of this title.

35 USC 102:
Conditions for patentability; novelty and loss of right to patent

A person shall be entitled to a patent unless -

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(e) The invention was describe on a patent granted on an application for patent by another filed in the United States before the invention thereof by the applicant for patent, or on an international application by another who fulfilled the requirements of paragraphs (1), (2), and (4) of section 371(c) of this title before the invention thereof by applicant for patent....
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5.  PCT article 39. This assumes that the applicants request PCT international examination. Otherwise, pursuant to PCT article 22, the PCT mandated delay is only 20 months from the earliest claimed priority date.
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6.  Manual of Patent Examining Procedure 6th Ed. Rev. 3 Section 1896 at page 1800-126 right-hand column lines 14-30.
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7.  United States provisional applications are provided for by 35 USC 111(b).
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8.  Private communication from Richard Lazarus, Esq. at the United States Patent and Trademark Office’s PCT legal office. See also, the 1996 report of the Commissioner of Patents.
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9.  The author has filed two of those petitions. Accordingly, the author is not unbiased.
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10.  In In re Lund, 376 F.2d 982, 988, 153 USPQ 625, 630-31 (CCPA 1967), the Court of Customs and Patent Appeals stated that “ it is also well settled that...all subject matter carried over into [the patent] from the parent application...[is] evidence to defeat another’s right to a patent.” (emphasis in the original). In In re Klesper, 397 F.2d 882, 885, 158 USPQ 256, 257 (CCPA 1968) the court unequivocally indicated that the 35 USC 102(e) prior art date of a patent is the filing date of the earliest United States filed application disclosing the invention from which the patent claims priority. More recently, the Federal Circuit has affirmed a long standing doctrine that prior art includes all inventions which were made in the United States and subsequently disclosed to the public in the United States. See E. I. Du Pont de Nemours & Co. v. Phillips Petroleum Co., 849 F.2d 1430, 1437, 7 USPQ2d 1129, 1134-35 (Fed. Cir. 1988) (quoting with approval from In re Bass, 474 F2.d 1276, 1292, 177 USPQ 178, 190 (CCPA 1973))(“[t]he term ’prior art’ as it is used in 35 U.S.C. §103 should include all inventions which were made in this country before an applicant or patentee made his invention, regardless of when those inventions are made public or patent applications on them are filed, so long as those inventions are found not to have been abandoned, suppressed, or concealed.”).
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11.  E. I. Du Pont de Nemours & Co. v. Phillips Petroleum Co., 849 F.2d at 1437, 7 USPQ2d at 1134-35 (Fed. Cir. 1988).
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12.  Hilmer, 359 F.2d at 878, 149 USPQ at 496 (CCPA 1966) (Rich J.)(“It seems clear to us that the prohibitions of 104, the limitations in sections 102(a) and 102(g) to “in this country,” and the specifying in 102(e) of an application filed “in the United States” clearly demonstrate a policy in our patent statutes to the effect that knowledge and acts in a foreign country are not to defeat the rights of applicants for patents, except as applicants may become involved in priority disputes.”)
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13.  While the PCT requires that the national phase examination begin no sooner than thirty months from the international applications’ earliest claimed priority date (if international examination is requested), most foreign applicants file their PCT applications (in their home country) just under one year after filing their foreign national applications and claim Paris Convention priority to their foreign national applications. This means that most foreign applicants enter the United States national stage eighteen months after filing their PCT application. The Commissioner has been assuming that the prior art date of a patent issued on a continuation of a PCT application is prior art as of the PCT application’s filing date, not on the date that the applicant completes the United States national stage requirements in the PCT application.
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14.  Under United States law, prior art may serve to limit what can be an infringement under the doctrine of equivalence. Thus, prior art that does not invalidate a claim in a patent may still be relevant to the scope of protection afforded by that claim.
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15.  The amendment to 35 USC 104 resulting from the Uruguay round of GATT allows foreign applicants to show proof of their invention prior to their foreign filing dates. However, 35 USC 102(b) provides that a printed publication published more than one year prior to “the earliest filing date in the United States” is statutory prior art and cannot be antedated by a 35 USC 104 showing of prior invention.
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16.  In fact the 35 USC 119(a) foreign priority statute contains language similar to 35 USC 102(b) reiterating that a foreign priority application does not count as a filing in the United States for purposes of the 35 USC 102(b) “one year bar” rule.
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17.  The statutory language supporting priority claims to provisional applications is modeled after the statutory language supporting priority claims to regular patent applications (35 USC 111(a) applications), and that language has been construed to provide prior art effect. See In re Klesper, 397 F.2d 882, 885, 158 USPQ 256, 257; and Hilmer, 359 F.2d at 879, 149 USPQ at 496-97. However, there is a line of cases starting with Alexander Milburn Co. v. Davis-Bournonville Co., 270 U.S. 390 (1926) suggesting that 35 USC 102(e) effect is limited to the earliest date on which an application could have issued, and a provisional application can never issue.
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Copyright Richard A. Neifeld.

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