What are the Priority Date, Patent Term, and Effective Filing Date of a Patent: The Roles of Specific Reference, Incorporation by Reference, and Claim Support

The Roles of Specific Reference, Incorporation by Reference, and Claim SupportA recent Federal Circuit decision demonstrates that for priority claims and patent term, the phrase “specific reference” is key. For example, amongst three related applications, to get the benefit of priority of an earlier U.S. patent application 1, application 3 in a priority claim has to have a “specific reference” to earlier application 1. A mere priority claim in application 3 to application 2, even though application 2 specifically “incorporates by reference” application 1, is not sufficient to allow application 3 to rely on the filing date of application 1. Rather, the priority chain is broken between applications 2 and 1, leaving application 3, at best, with a priority date of application 2 for purposes of patentability.

Furthermore, a recent district court decision highlights that there must be nothing more than a “specific reference” in the later patent application to the earlier patent application to start the patent clock with the date of the earlier patent application. And, whether or not any claim in the later application is entitled to priority in the earlier application for patentability purposes requires “specific reference” to the earlier application.

There is, therefore, one date for patent term expiration, irrespective of whether or not claims in that patent have different effective filing dates. That, of course, is different for entitlement to a claim to priority for patentability purposes, which is determined on a claim-by-claim basis.

This article analyzes two recent cases for practical lessons when (1) drafting and prosecuting patent applications and (2) analyzing issued U.S. patents in the context of freedom to operate and/or due diligence.

Recent Cases

  1. Droplets, Inc. v. E*Trade Bank: Incorporation by Reference Fails to Avoid a Break in the Priority Chain

Droplets, Inc. v. E*Trade Bank, 887 F.3d 1309 (Fed. Cir. 2018), arose from an appeal of a Final Written Decision in an inter partes review. In E*TRADE Fin. Corp. v. Droplets, Inc., IPR2015-00470 (P.T.A.B. June 23, 2016), the Patent Trial and Appeal Board (“PTAB” or “Board”), held all instituted claims of U.S. Patent No. 8,402, 155 (“the ’115 patent”) unpatentable. In particular, the ’115 patent failed to enumerate a priority claim sufficient to avoid fully-invalidating prior art; the incorporation by reference of an earlier priority document failed to satisfy the patentee’s burden of providing notice of the asserted earlier priority date under 35 U.S.C. § 120.” Id. at 1311.

The chart below summarizes the challenged claim priority language. It was undisputed that the ‘115 patent’s priority claim to U.S. Patent No. 7,502,838 (“the ‘838 patent”) was proper, and that the ‘838 patent’s priority claim to U.S. Provisional Application No. 60/153,917 (“the ’917 application”) priority date was proper. Id. at 1313. The issue was whether the ‘115 patent was entitled to the ‘917 provisional application priority date, particularly when the ’115 patent did not contain a specific reference to either an intervening U.S. Patent No. 6,687,745 (“the ‘745 patent”) or the ’917 provisional application, but only “incorporated the ’838 Patent by reference.” Id.

For priority purposes, the statutes (35 U.S.C. §119(e)(1) and §120) and regulation (37 C.F.R. §1.78) both require co-pendency and a specific reference to the earlier filed application. The Federal Circuit affirmed that the “Board correctly applied § 120 in finding that the ’115 Patent claims priority only to the ’838 Patent.” Id. at 1316. The ’115 patent is a continuation of the ’838 patent and only contained specific reference to the ‘838 patent.

During prosecution of the ‘115 patent, the USPTO issued a filing receipt with a priority claim to the ‘745 patent. Subsequently, the USPTO issued a corrected filing receipt indicating that the priority claim was solely to the ‘838 patent, leaving out the ‘745 patent and the ‘917 provisional application. The ’115 patentee failed, during prosecution, to challenge the corrected filing on this issue.

Both the PTAB and the Federal Circuit indicated that the failure to make specific reference to the ‘745 patent broke the priority chain. Incorporation by reference in the ‘115 patent of the ‘838 patent, even though the ‘838 patent indisputably made specific reference of priority to the ‘745 patent, was not enough to provide specific reference to the ‘745 patent in the chain of priority for the ‘115 patent.  At best for the purposes of priority, the ’115 patent’s effective filing date is November 24, 2003, the filing date of the ’838 patent. Because of the priority date accorded the ‘115 patent, the PCT publication, with an identical specification, was prior art that rendered the claims unpatentable. With the broken chain of priority, the unpatentability determination of the PTAB was affirmed.

While the defendant argued that this was all based on a hypertechnicality, the Federal Circuit reaffirmed a strict reading of the statutes (35 U.S.C. §119(e)(1) and §120). That strict reading acknowledged the “important public policy” of public notice. The Federal Circuit explained:

That the ’115 Patent fails to enumerate a priority claim sufficient to avoid Droplets’ own fully-invalidating prior art is not a “hypertechnicality” that unfairly rendered the claims unpatentable. Section 120 places the burden on the patent owner to provide a clear, unbroken chain of priority. [Medtronic CoreValve, LLC v. Edwards Lifesciences Corp., 741 F.3d 1359, 1366 (Fed. Cir. 2014)].

Id. at 1317,

Further rejecting Droplets’ arguments to construe the incorporation by reference as sufficient to avoid a break in the priority chain, the Federal Circuit also turned to 37 C.F.R. §1.57 noting that:

[N]othing in regulation 1.57 authorizes making a priority claim under § 120 through an incorporated reference. … The words of a priority claim are  … separate from the materials necessary to satisfy § 112. Accordingly, while 37 C.F.R. § 1.57 authorizes an applicant to incorporate by reference essential and nonessential material to satisfy § 112, nothing contained therein permits incorporating a priority claim by reference.

Id. at 1319-20.

The Federal Circuit concluded that the requirements of § 120 cannot be met by incorporation by reference. Rather, “a patent must contain a specific reference to each prior-filed application to be entitled to those applications’ earlier filing dates.” Id. at 1322. “Droplets’ proposed reading of § 120 conflicts with the statute’s purpose, which is to provide clear notice to the public of the patentee’s claimed priority date.” Id. at 1320. That is, “[t]o require the public to search for an unstated priority claim through incorporated materials would create uncertainty and would require the type of guess-work that the statue is meant to avoid.” Id.

  1. Clinicomp Int’l, Inc. v. Cerner Corp.

Clinicomp Int’l, Inc. v. Cerner Corp., Case No. 17-cv-2479 (S.D. Cal. May 16, 2018) highlights the issue of priority in the context of the patent term. In Clinicomp Int’l, resulting in a grant of defendant’s motion to dismiss, there were two issues:

(1) whether the patent term started on November 24, 1997, and

(2) whether the patentee can obtain the benefit of a grandparent filing date of February 1995 to start the patent term, even though there was no specific reference in the patent in suit to the grandparent application.

With respect to patent term, which could be relevant to issues such as the scope of alleged patent infringement and potential damages, the court concluded that lack of specific reference in the patent in suit to the grandparent application precluded the patent term from starting at the February 28, 1995, filing date of the grandparent.

In particular, Plaintiff’s patent at issue, U.S. Patent No. 6,665,647 (“the ‘647 patent”), specifically referenced the parent application, U.S. Application No. 08/977,522 (“the ‘522 application, which was filed Nov. 24, 1997). The ‘647 patent was a continuation-in-part of the ‘522 application, which was a continuation application of U.S. Application No. 08/396,004 (“the ‘004 application).  The ‘647 patent failed to specifically reference in its chain of priority the ‘004 grandparent application.  By way of diagram, the chain of priority is illustrated below:

Defendant asserted that the ‘647 patent’s filing date is the ‘004 grandparent application’s, meaning the ‘647 patent’s expiration date would be Feb. 28, 2015, i.e., twenty years from the ‘004 application’s filing date. It was undisputed that the ‘647 patent did not specifically reference the ‘004 application, but only the ‘522 application.

The ‘522 application, however, specifically referenced the ‘004 application; was that enough to start the patent term clock? No. The district court held that “since the ‘647 patent does not specifically reference the grandparent ‘004 Application, and there has been no amendment or correction filed with the PTO, the ‘647 patent does not obtain the benefit of the ‘004 Application filing date.” Id. at 19. The district court cited the Federal Circuit’s “strict reading of the § 120 specific reference requirement” in Droplets and the emphasis on the importance of public notice. Id. at 18.

The priority date also implicated the patent term expiration date for the ‘647 patent, particularly whether or not any claim of the ‘647 patent had to be supported in earlier patent application(s) for purposes of starting the patent term clock.  The district court concluded that the priority claim itself was per se sufficient to start the patent term clock to determine the expiration date.  No analysis was needed of whether any patent claim of the patent in suit was in fact demonstrated to be entitled to that priority date.

That is, for the patent term clock to start, there is no requirement that any claim be demonstrated to have written description and enablement under § 112(a) in the “clock starting” patent application. Id. at 12. Instead, all that is required is specific reference to an earlier patent application.

Here, the ‘647 patent contained a specific reference to the earlier-filed ‘522 application; the patent term clock started from the filing date of the ‘522 application. Unfortunately, the expiration date of Nov. 24, 2017, was two weeks prior to the filing of the infringement complaint, so the willful infringement and induced infringement claims were dismissed. Id. at 4.

Prosecution Takeaways

From the Federal Circuit in Droplets, practitioners are reminded that both priority claims and incorporation by reference are very specific tools that should not be relied on during prosecution without careful consideration and deliberate use. See also, MPEP §211. Certainly, incorporation by reference does not trump “specific reference” and may lead to a break in the priority chain for purposes of patentability.

Clinicomp, a district court decision, illustrates that the patent term clock starts based on nothing more than a specific priority reference to a priority application, whether or not any claim in the patent is supported under § 112(a) in that priority application.  There is no need to demonstrate that the claims are entitled to priority, as would be required if there was an attempt to establish patentability of those claims over prior art arising after the priority application date. Starting the patent term clock and having basis for a priority claim for patentability purposes are entirely different concepts, even though both concepts require specific reference to the earlier document.

Given the specific reference requirement, every patent claim will expire at the same time, whether or not supported in the “clock starting” patent document.  In contrast, for purposes of patentability, entitlement to priority is determined on a claim-by-claim basis, leaving open the possibility that different claims will have different effective filing dates.

Clinicomp also reminds us to clearly assess whether a priority application is worth specifically referencing. If that priority application adds nothing to patentability, why specifically reference it? Claiming priority in such a case does nothing except lose patent term at the end of the patent cycle.  Ironically, in such a case, the patentee may want to consider breaking the chain of priority to achieve a later patent expiration.

Specific reference, incorporation by reference, and claim support are, of course, relevant in the context of due diligence or freedom-to-operate analyses. When does the patent term clock start? If it is early enough, the patent may be expired before a suit was filed, as in Clinicomp.  And if the priority chain is broken, the claims are vulnerable to invalidity attacks, as in Droplets.


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Join the Discussion

2 comments so far.

  • [Avatar for Pro Say]
    Pro Say
    November 3, 2018 07:04 pm

    Yes; thank you all for this excellent article; and for your comments Perkins.

    A word to the wise then: Recite the chain in the 1st paragraph AND recite it in the ADS.

    Do both.

  • [Avatar for Perkins]
    October 31, 2018 01:47 pm

    Thank you Ms. Burgy, Mr. Irving and Ms. Lewis for this excellent article. The information you present is a wonderful example of yet other wrong headed and illogical ways the PTAB, as upheld by the Federal Circuit, have changed long established patent laws. Unlike litigants of the past arguing over claim meanings, it is now the PTAB and Federal Circuit that are twisting laws like the famous ‘nose of wax.’ This needs to go to the SCOTUS, although that too may have the same illogical outcome.

    In Clinicomp, the statement “… there has been no amendment or correction filed with the PTO…” causes me to wonder when the explicit language, either a claim of, or a disclaimer of priority, can be added. In the case of correcting to add specific claim of priority language, there is clear support in the specification of the later filed patent via the incorporation by reference. I would think that it should be possible to cure the priority with a post issuance certificate of correction. For a disclaimer, under this case law, if there is no explicit claim of priority then a post issuance disclaimer should be effective. Of course, that might be too logical for the PTAB.

    And one last comment. I wonder how long it will be before the PTAB decides that reciting the chain of priority in the Application Data Sheet is inadequate without also reciting the chain in the 1st paragraph of the specification because to require the public to search the ADS for a priority claim would create uncertainty and guess-work.