Authored by Hope Techlin
Two burdens generally frame priority disputes in post-grant proceedings: the burden of persuasion and the burden of production. When those burdens arise in the context of priority claims under 35 U.S.C. §§ 119 and 120, the question of which party bears each burden, and what each party must show to satisfy that burden, has long been an important issue in patent practice.
Burden of Persuasion v. Burden of Production
Dynamic Drinkware, LLC v. National Graphics, Inc., 800 F.3d 1375 (Fed. Cir. 2015), lays out the major differences between the burden of persuasion and the burden of production. The burden of persuasion is “the ultimate burden assigned to a party who must prove something to a specified degree of certainty,” such as by a preponderance of the evidence or by clear and convincing evidence. Id. at 1378 (quoting Tech. Licensing Corp. v. Videotek, Inc., 545 F.3d 1316, 1326–27 (Fed. Cir. 2008)). In post-grant proceedings, the petitioner carries the burden of persuasion to prove unpatentability by a preponderance of the evidence. 35 U.S.C. § 316(e); Dynamic Drinkware, 800 F.3d at 1378. That burden remains with the petitioner and “never shifts to the patentee.” Id.
The burden of production is different, shifting between the petitioner and patent owner depending on the stage of the proceeding and the priority issue being raised. Dynamic Drinkware, 800 F.3d at 1379–80; Tech. Licensing, 545 F.3d at 1327. For example, a petitioner first carries the burden of production by identifying prior art that could invalidate the challenged claims. Once that showing is made, the patent owner may then need to come forward with evidence showing that the challenged claims are entitled to an earlier filing date under 35 U.S.C. § 120. Research Corp. Techs., Inc. v. Microsoft Corp., 627 F.3d 859, 871 (Fed. Cir. 2010); Tech. Licensing, 545 F.3d at 1326–27; PowerOasis, Inc. v. T-Mobile USA, Inc., 522 F.3d 1299, 1305–06 (Fed. Cir. 2008); Google LLC v. AGIS Software Dev., LLC, IPR2018-01082, Paper 10 at 18–19 (P.T.A.B. Nov. 20, 2018). If the patent owner makes that showing, the burden of production can shift back to the petitioner to show that the asserted reference is entitled to an even earlier filing date, including through a provisional application under 35 U.S.C. § 119(e). Dynamic Drinkware, 800 F.3d at 1379–82.
This burden shift has played a significant role in the finding of many cases surrounding provisional priority claims for both asserted patents and prior art references. This then raises the question as to how this burden changes in the context of § 119(e) versus § 120 and what the specific requirements are for each during this process.
Burden of Production under 35 U.S.C. § 120 Priority Claims
The burden of production under 35 U.S.C. § 120 arises when a patent owner attempts to rely on an earlier non-provisional application, or a chain of earlier applications, to establish an earlier priority date. As previously mentioned, this burden shifts to the patent owner once the petitioner identifies potentially invalidating prior art, at least where the examiner did not expressly address priority during prosecution. Google, IPR2018-01082, Paper 10 at 18. At that point, the patent owner must show not only that the earlier application exists, but also “why the written description in the earlier application supports the claim.” Tech. Licensing, 545 F.3d at 1327. This makes the written description inquiry central to the § 120 analysis because the patent owner must show that the earlier disclosure reasonably conveyed possession of the claimed invention as of the earlier filing date. Ariad Pharms., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed. Cir. 2010) (en banc).
This burden becomes particularly important when the patent owner relies on a priority chain. In that setting, the patent owner must show that each application in the chain provides written description support for the challenged claims. In re Schneider, 481 F.2d 1350, 1356 (C.C.P.A. 1973); Zenon Envtl., Inc. v. U.S. Filter Corp., 506 F.3d 1370, 1378 (Fed. Cir. 2007). Thus, it is not enough to show that the earliest application contains some related disclosure. The patent owner must instead connect the challenged claims to the written description in each application needed to complete the priority chain and show support “with respect to the subject matter presently claimed.” In re Schneider, 481 F.2d at 1356. The Board’s decision in Google illustrates the point. There, the patent owner claimed priority through a chain of continuation-in-part applications back to a 2004 application but offered no analysis or evidence identifying where that application, or any intervening application, described the claimed “server” and Internet Protocol address limitations. Google, IPR2018-01082, Paper 10 at 15, 21–23. The Board explained that it was “incumbent on Patent Owner, not Petitioner,” to demonstrate entitlement to the earlier date, and it held that the patent owner had not established entitlement to that or any other priority date. Id. at 22–24.
Accordingly, the burden of production under § 120 is generally met by showing: (1) the existence of the earlier application or applications; and (2) written description support for the challenged claims in each application being relied upon for priority. Tech. Licensing, 545 F.3d at 1327; Research Corp., 627 F.3d at 871; Google, IPR2018-01082, Paper 10 at 19.
Burden of Production under 35 U.S.C. § 119(e) Priority Claims
The burden of production under 35 U.S.C. § 119(e) arises in a different way than the burden under § 120. Instead of a patent owner relying on an earlier application to establish the priority date of its own claims, § 119(e) comes up when a petitioner relies on an earlier provisional filing date to establish that an asserted reference qualifies as prior art. In that circumstance, the petitioner bears the burden of production to prove that the reference is entitled to the benefit of its provisional filing date, although that burden does not arise until the patent owner comes forward with evidence antedating the reference’s non-provisional filing date. Dynamic Drinkware, 800 F.3d at 1380–81. Under Dynamic Drinkware, a petitioner relying on a provisional filing date for a pre-AIA prior art reference had to show that the provisional provided written description support for the claims of the later reference patent. The Federal Circuit explained that “[a] provisional application’s effectiveness as prior art depends on its written description support for the claims of the issued patent of which it was a provisional.” Id. at 1382. Because the patent at issue was governed by pre-AIA § 102(e), however, the court noted that it was not interpreting the AIA’s impact in “newly designated § 102(d).” Id. at 1381 n.2.
That rule became more complicated for post-AIA references when the PTAB took a different approach in Penumbra, Inc. v. RapidPulse, Inc., No. IPR2021-01466, Paper 34, 2023 WL 2605070 (P.T.A.B. Mar. 10, 2023) (precedential). In Penumbra, the Board determined that AIA § 102(d) did not require the petitioner to show that the provisional application supported at least one claim of the later reference patent. Instead, the Board concluded that a reference patent only needed to satisfy the “ministerial requirements” of §§ 119 and 120 and show that the earlier application described the subject matter being relied upon as prior art. Id. at 32.
The Federal Circuit recently rejected that approach in Dental Monitoring SAS v. Align Technology, Inc., 184 F.4th 1376, 1379–82 (Fed. Cir. 2026). There, the court held that AIA § 102(d)(2)’s phrase “entitled to claim a right of priority” incorporates the substantive requirements of § 119(e)(1), including the written description requirement under § 112(a). Id. at 1379–80. The court also rejected the argument that Dynamic Drinkware applies only to pre-AIA patents, explaining that the argument “confuses a reservation of decision with a holding on the merits.” Id. at 1381. Dynamic Drinkware’s opinion declining to address § 102(d) reflected only that the question was not before the court, and the concern underlying that decision, that a challenger should not be able to backdate prior art through a provisional that would not have supported a patent on the claimed invention, “still remains valid.” Id. The court therefore concluded that, to use the provisional filing date of the asserted reference, the petitioner had to show written description support for at least one claim of that reference, as described in the pre-AIA precedent set under Dynamic Drinkware. Id. at 1381–82.
Accordingly, the burden of production under § 119(e), when used to establish a prior art reference’s provisional filing date, requires more than simply pointing to the provisional application and the relied-upon disclosure. After Dynamic Drinkware and Dental Monitoring, the petitioner must show for both pre- and post-AIA prior art references that: (1) the reference satisfies the formal requirements of § 119(e); (2) the provisional describes the subject matter relied upon in the reference; and (3) the provisional provides written description support for at least one claim of the reference. Dynamic Drinkware, 800 F.3d at 1381–82; Dental Monitoring, 184 F.4th at 1381–82. Without each of these showings, the petitioner has not met its burden of production for relying on the provisional filing date.
Important Takeaways
When looking at the burden of proof for post-grant proceedings, it is important for both the petitioner and the patent owner to understand which burden they carry and what that burden requires. The petitioner always carries the ultimate burden of persuasion to prove unpatentability, and that burden never shifts. The burden of production, however, can shift depending on the priority issue being raised. Under § 120, a patent owner relying on an earlier non-provisional application, or a chain of earlier applications, must show written description support for the challenged claims in each application needed to establish priority. Under § 119(e), when a petitioner relies on a provisional filing date for an asserted prior art reference, whether governed by pre-AIA § 102(e) or AIA § 102(d)(2), the petitioner must do more than point to the provisional and the relied-upon disclosure. The petitioner must show that the provisional meets the formal requirements of § 119(e), describes the subject matter relied upon, and provides written description support for at least one claim of the reference.
Priority should not be assumed simply because it is claimed. Whether under § 119(e) or § 120, the party relying on the earlier filing date must be prepared to prove that the earlier application provides the necessary written description support and meets the formal requirements necessary for each respective statute.
About the Authors
John Rondini is a Shareholder and co-chair of Brooks Kushman’s Intellectual Property Litigation practice, representing clients in patent disputes, cybersecurity and data privacy matters, and complex technology-related litigation. His practice also includes Patent Prosecution, Post-Grant Proceedings, and the negotiation of Licensing & Agreements. Drawing on his prior experience as a hardware design and software engineer, John counsels clients in the Automotive and Mobility Brands & Technology, Electrical & Computer Technology, and Information Technology Services & Software industries. He helps clients protect innovation, address data security risks, and develop intellectual property strategies aligned with their business objectives.
Hope Techlin is a senior Electrical Engineering student at the University of Michigan College of Engineering with a minor in Art & Design who plans to pursue a career in patent law. Through her experience as a Summer Intern at Brooks Kushman, she has gained exposure to Patent Prosecution and Intellectual Property Litigation, including patent application drafting and work related to infringement and invalidity contentions. Her technical background makes her particularly interested in innovations within Electrical & Computer Technology and Artificial Intelligence & Data-Driven Technologies. Hope combines analytical problem-solving skills, engineering experience, and a strong interest in intellectual property to support innovators and emerging technologies.
About Brooks Kushman P.C.
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