A published application must show written description support for both its claims and the specific subject matter relied upon as prior art, under a clarified standard for provisional priority.
Reining in Reach-Back: The Riggs Rule
Under U.S. patent law, published patent applications may serve as prior art as of their provisional patent application filing dates, provided certain conditions are met. The Federal Circuit’s recent decision in In re Riggs, No. 2022-1945 (Fed. Cir. Mar. 24, 2025), introduced an important new requirement. Decided under pre-AIA 35 U.S.C. § 102(e), the case holds that it is not enough for a provisional application to support a claim in the published application. To qualify as prior art as of the provisional’s filing date, the specific subject matter actually relied on in the rejection must also find written description support in the provisional. This decision sharpens and builds upon prior rulings like Dynamic Drinkware, LLC v. National Graphics, Inc., 800 F.3d 1375 (Fed. Cir. 2015) and Amgen Inc. v. Sanofi, 872 F.3d 1367 (Fed. Cir. 2017), and raises the bar for both examiners and practitioners seeking to rely on provisional filings in prior art analysis.
The Facts and Timeline: What Happened in In re Riggs
The In re Riggs decision arose from a dispute over whether a published patent application, US 2002/0049622 to Lettich et al., qualified as prior art against the applicants’ logistics-focused patent application under pre-AIA § 102(e). The central issue was whether the Lettich publication could benefit from the filing date of its provisional application for prior art purposes.
The key dates are summarized as follows:
April 27, 2000, Lettich Provisional
July 28, 2000, Riggs Provisional
April 26, 2001, Lettich Non-Provisional
April 25, 2002, Lettich Publication
December 7, 2004, Riggs Non-Provisional
As outlined above, the Riggs application claims a provisional priority date that predates the filing of the Lettich non-provisional application – but follows the filing of the Lettich provisional.
The USPTO examiner rejected several claims of the Riggs application as anticipated or obvious in view of Lettich. The Patent Trial and Appeal Board (PTAB) ultimately agreed with the examiner and upheld the rejections, finding that the Lettich provisional provided adequate written description support for claim 1 of the Lettich published application under the Dynamic Drinkware test. The applicants appealed, leading to the Federal Circuit’s decision in In re Riggs.
The Court’s Holding: A Two-Part Test Emerges
In clarifying the test for prior art status under § 102(e), the Federal Circuit vacated the PTAB’s decision, holding that it had applied an incomplete legal standard.
Previous Federal Circuit decisions had already required that the claims of a published application be supported by the written description of a provisional application to claim its earlier filing date. In Dynamic Drinkware, the court held that provisional support for at least one claim was necessary to establish effective prior art status. Amgen similarly emphasized the need for robust written description in evaluating priority.
Neither decision addressed whether the provisional must also support the specific disclosure relied on in a rejection. That question is now resolved in Riggs. To qualify as prior art as of its provisional date, a published patent application must also show that the particular subject matter used in the rejection is itself supported by the provisional’s written description. In other words, the reach-back to a provisional filing date does not extend to the entire disclosure unless that disclosure, like the claims, is adequately described in the provisional.
This effectively creates a two-part test:
- At least one claim of the published application must be supported by the provisional (as articulated in Dynamic Drinkware).
- The actual subject matter cited in the rejection must also be supported by the provisional (as now required by Riggs).
The court emphasized the logic of this approach, stating:
“It makes no sense to suggest that if a single claim is supported by the provisional application, then everything in the later filed application gets the benefit of the provisional date whether supported or not.”
In practical terms, a reference cannot reach back to a provisional filing date for all that it discloses simply because one of its claims is adequately supported. If the examiner relies on a paragraph, figure, or feature to reject another application, that specific material must be traceable to the provisional in accordance with written description standards.
Confirming USPTO Guidance
Notably, the two-part test articulated in Riggs aligns with existing USPTO guidance. Section 2136.03 of the MPEP provides that a provisional application must support both the claims and the specific subject matter cited in a rejection to serve as effective prior art. Riggs does not depart from that guidance but confirms and formalizes it at the appellate level. In doing so, the Federal Circuit has provided practitioners with a clearer framework for evaluating provisional priority in prior art analysis.
Implications for Patent Applicants and Practitioners
This clarification signals a shift in how practitioners evaluate prior art tied to provisional filings. For many years, once a provisional was found to support at least one claim of the published application, the earlier effective date was often presumed.
Riggs shifts the analysis by requiring that the specific paragraph, figure, or feature used in a rejection also be described in sufficient detail in the provisional to meet written description standards. This is more than a procedural nuance; it can materially influence how priority claims are assessed and how rejections are approached during prosecution.
For those drafting applications — especially provisionals —Riggs reinforces the value of thorough disclosure. It’s not enough to focus solely on supporting later claims; to fully preserve the provisional’s potential value as prior art, the specific subject matter disclosed must also be clearly described up front. This means thinking beyond just claim support and anticipating what features or embodiments might later serve as grounds for anticipation or obviousness. A well-drafted provisional does double duty: it lays the groundwork for the applicant’s own priority claims and strengthens the application’s ability to stand as prior art against competitors.
For those responding to rejections, Riggs offers a powerful tool: it requires that the specific disclosure relied upon in a rejection be adequately supported by the cited reference’s provisional application. This goes beyond showing that a single claim is enabled — the examiner or petitioner must demonstrate that the actual disclosure being used as prior art is clearly described in the provisional. That opens the door to a compelling timing argument: if the relied-upon content cannot be traced back with written description-level support, the reference may lose its earlier effective date. This creates a targeted and potentially decisive basis for challenging rejections grounded in questionable priority claims.
For practitioners conducting due diligence, freedom-to-operate assessments, validity analyses, pre-litigation review, or similar evaluations, Riggs adds an important layer of scrutiny. When a reference patent or published application is asserted as prior art based on an earlier provisional filing, the claimed priority date should not be accepted at face value. The key question is whether the specific subject matter of interest is actually described in the provisional application.
This analysis requires more than confirming the existence of a formal priority claim — it invites a direct, disclosure-level comparison between the relevant subject matter in the later-filed application and the content of the provisional. Practitioners should examine whether the provisional actually contains written description-level support for the specific disclosure being evaluated. In some instances, the provisional may omit or only broadly reference the relevant content, leaving the effective date anchored to the later non-provisional filing. Identifying such gaps can inform a range of strategic decisions, such as assessing competitive filing timelines, evaluating invalidity positions, or determining the availability of a freedom-to-operate path.
Riggs and Post-AIA Practice
Although Riggs arose under pre-AIA § 102(e), its reasoning is instructive under the post-AIA framework — particularly with respect to § 102(d), which governs the effective date of prior art disclosures in U.S. patents and published applications. That provision requires that the subject matter relied upon as prior art be “described” in the earlier application. While the Riggs decision does not interpret § 102(d) directly, it establishes that claim-level support alone does not suffice; the specific disclosure cited in the rejection must be supported in the provisional to satisfy the written description standard. This reinforces a disclosure-focused approach consistent with the AIA statutory language and existing USPTO guidance.
Practitioner’s Takeaway: Shift from Claim-Centric to Disclosure-Centric Thinking
Riggs confirms that the effective prior art date of a published application turns not only on whether its claims are supported by a provisional, but also on whether the specific subject matter cited in a rejection is adequately described in that provisional. This represents a shift from claim-level analysis to a more precise focus on the actual disclosure. In practice, this means that when analyzing the priority of a reference — whether pre- or post-AIA — practitioners should look beyond claim support and confirm that the actual subject matter being cited is clearly described in the provisional application. For practitioners, it underscores the need for careful drafting and review, and offers a clearer framework for evaluating priority in both prosecution and strategy.
