Imagine That IP Law Blog

The terrain of inter partes review (IPR) strategy shifted meaningfully on November 17, 2025. On that date, the USPTO issued a memorandum authorizing voluntary Search Disclosure Declarations (SDDs), positioning them as a pro‑institution factor in IPR and PGR practice. At first glance, the SDD looks like a one‑way ratchet in petitioners’ favor: disclose your search methodology, strengthen your story of Office error, and improve your institutional odds. But once Ironburg Inventions Ltd. v. Valve Corp. is layered on top of the new guidance, the calculus becomes more complicated. The same declaration that buys marginal leverage at the PTAB can later become powerful estoppel evidence in district court, where the Federal Circuit has now entrenched a “skilled searcher” standard for § 315(e)(2).

I. The Ironburg Standard: A Hypothetical Searcher with Real Consequences
Any analysis of SDD risk must start with Ironburg. Section 315(e)(2) bars an IPR petitioner from later asserting “any ground that the petitioner raised or reasonably could have raised during” the IPR in a civil action. 35 U.S.C. § 315(e)(2). In Ironburg, the Federal Circuit confronted how this language applies to invalidity theories based on prior art that was not in the petitioner’s original IPR petition but surfaced later via another company’s petition against the same patent.

The district court had followed a formulation that had been gaining traction in the lower courts: a ground is estopped if it relies on prior art that “a skilled searcher conducting a diligent search reasonably could have been expected to discover” at the time of the petition. Ironburg Inventions Ltd. v. Valve Corp., 64 F.4th 1274, 1298 (Fed. Cir. 2023). The Federal Circuit expressly endorsed this “skilled searcher” standard, holding that it fits the text of § 315(e)(2) and the estoppel framework elaborated in cases like Cal. Inst. of Tech. v. Broadcom Ltd., 25 F.4th 976 (Fed. Cir. 2022) (en banc).

Crucially, Ironburg characterizes the test as objective. The estoppel inquiry is not an autopsy of what the petitioner’s actual team did or did not find; it asks what a hypothetical searcher—skilled in prior‑art searching in the relevant technology and exercising reasonable diligence—“reasonably could have” discovered when the petition was filed. Ironburg, 64 F.4th at 1298–99. At the same time, the court drew a clear line between “reasonable diligence” and “scorched earth” tactics, rejecting the idea that estoppel requires a worldwide, limitless hunt for every obscure reference. Id. at 1299 (approving Clearlamp’s refusal to demand “a scorched‑earth search around the world”).

For patent owners, the most important part of Ironburg is the burden of proof. The district court had effectively required Valve, the accused infringer, to show that a diligent, skilled searcher would not have found the later‑asserted references. The Federal Circuit reversed, holding that § 315(e)(2) estoppel is an affirmative defense and the burden lies with the party asserting it. Id. at 1299. The patent owner must prove, by a preponderance of the evidence, that a skilled searcher exercising reasonable diligence would have discovered the prior art now being used in litigation. Id. (vacating and remanding because the district court had improperly placed the burden on Valve).

Ironburg thus gives petitioners a doctrinal shield: estoppel extends only to what a reasonably diligent hypothetical searcher would find, and it is the patent owner’s job to prove that point with real evidence.

II. The New Variable: Search Disclosure Declarations at the PTAB
Into this landscape the USPTO has introduced a new, seemingly petitioner‑friendly tool. On November 17, 2025, the Office issued a memorandum on “Voluntary Search Disclosure Declarations as a Favorable Factor in Institution Decisions.” U.S. Patent & Trademark Office, Memorandum, Voluntary Search Disclosure Declarations as a Favorable Factor in Institution Decisions 1 (Nov. 17, 2025) [hereinafter SDD Memo]. The memo authorizes parties to file a voluntary SDD with their IPR or PGR petition, describing how they found the prior art on which the petition relies.

The SDD is meant to be granular. The memorandum contemplates that petitioners will disclose which databases and repositories they searched, how they structured their searches (including search terms, filters, and classification pathways), what analytics and public resources they consulted, and how much time they spent running searches and reviewing results. SDD Memo, supra, at 1. The Director explicitly notes that these disclosures may reveal “sophisticated search methodologies” and analytics that the Office itself does not routinely use. Id.

The carrot is straightforward. The memorandum states that the submission of an SDD will be treated as a “non‑exclusive, non‑dispositive favorable discretionary factor supporting institution,” particularly when it shows that petitioners relied on search strategies beyond those used in examination to uncover new, material prior art. Id. at 2. By documenting that their prior‑art search outpaced the examiner’s, petitioners can strengthen the argument that the PTAB should institute review to correct potential Office error. The memo also signals that the Office intends to use SDD information to “meaningfully improve Office search practices and, over time, improve examination quality.” Id. at 1.

Formally, SDDs are voluntary. The memo reassures parties that “a petitioner who does not provide an SDD will not be disadvantaged.” Id. at 1. In practice, however, once a mechanism for earning a pro‑institution factor exists, petitioners in close cases will feel pressure to use it—particularly where Fintiv‑style discretionary denial still looms in the background.

III. The Collision: When Disclosure Helps Define Diligence
On paper, SDD practice and Ironburg’s estoppel standard occupy different procedural universes. The SDD is a front‑end, PTAB‑facing tool aimed at institution and examination quality. Ironburg governs back‑end, district‑court estoppel after the PTAB has issued a final written decision. The risk arises because both are, in effect, about the same thing: what a reasonable prior‑art search in a given field looks like.

Under Ironburg, the “skilled searcher” is a hypothetical construct. The court is not supposed to ask what the particular petitioner’s team did; it is supposed to ask what a competent search professional, acting diligently in that field, would have found using reasonable methods. Ironburg, 64 F.4th at 1298–99. The SDD, by contrast, transforms the hypothetical into something concrete. By filing an SDD, the petitioner puts on the record a detailed description of what it says it actually did: which commercial tools it used, which non‑standard repositories it tapped, which classification pathways it followed, and how intensively it reviewed the results.

For purposes of PTAB advocacy, the more sophisticated that description, the better. Petitioners want to show that their search was materially more powerful than examination, that the art they rely on was readily accessible using the tools they chose, and that the Board should therefore step in to correct a gap in the Office’s earlier work. From an estoppel perspective, however, the same disclosure can look very different.

If later, in district court, the petitioner advances invalidity theories based on art that sits in the very databases, classification schemes, or analytics frameworks that the SDD showcases, the patent owner can argue that the petitioner has already defined what diligence looks like. Ironburg places the burden on the patent owner to prove what a skilled searcher using reasonable diligence would have found. Id. at 1299. An SDD filled with advanced techniques and extensive time commitments gives the patent owner precisely the evidentiary foundation it needs to meet that burden.

In other words, the SDD can collapse the distance between the objective Ironburg standard and the petitioner’s subjective capabilities. Instead, a hypothetical searcher starts to look a lot like this petitioner, at this moment, with these resources. When the petitioner later misses a reference that was available through the same channels it described in the SDD, the patent owner can argue that, under Ironburg, such a reference is estopped because it is exactly the kind of art a skilled searcher, employing the disclosed methods, “reasonably could have been expected to discover.” Ironburg, 64 F.4th at 1298.

IV. The Mirage of Confidentiality
The SDD memorandum attempts to address practitioner anxiety by providing confidentiality mechanisms. Petitioners may file SDDs as “Filing Party and Board” documents, accompanied by a motion to seal and a request for in camera review under 37 C.F.R. § 42.14. SDD Memo, supra, at 2. The memo further states that deposition testimony concerning SDDs will not be permitted “absent extraordinary circumstances.” Id.

Those assurances, however, are confined to the PTAB’s procedural universe. The Board’s rules do not bind Article III judges managing discovery in infringement litigation. Once a patent owner asserts § 315(e)(2) estoppel under Ironburg, the content of any SDD filed in the earlier IPR becomes highly probative of what the petitioner’s search looked like and what a skilled searcher might reasonably have done. A district court may conclude that the SDD—and the search methodology it describes—is squarely relevant to whether the patent owner has carried its burden to show that the later‑asserted art “reasonably could have been” raised in the earlier IPR. See Ironburg, 64 F.4th at 1298–99.

Nor does PTAB sealing guarantee insulation in district court. A federal judge addressing estoppel can order production of the SDD subject to a protective order, treat it as confidential litigation material, and still permit each side’s experts to dissect it in detail. Once disclosed, the SDD becomes a ready‑made script for the patent owner’s search expert: here are the databases, the queries, and the classification pathways that a sophisticated petitioner deemed appropriate at the time; here is how the later‑asserted art fits within that pattern.

In that setting, the SDD’s initial confidentiality looks increasingly like a mirage. It may limit public access and cabin PTAB‑specific discovery, but it does not eliminate the risk that the same document will later be used to build the patent owner’s estoppel case under Ironburg.

V. Practical Implications and Strategic Balance
Ironburg provided petitioners with meaningful protection by defining the “skilled searcher” as someone exercising reasonable, not extraordinary, diligence, and by assigning the burden of proving that standard to patent owners. The SDD framework offers petitioners a new sword for cutting through discretionary denials: by laying bare the mechanics of their prior‑art searches, they can make a stronger case that institution is warranted to correct Office error and to consider art unearthed by superior private‑sector tools.

But the sword has two edges. Every detail a petitioner chooses to disclose in an SDD—every reference to bespoke analytics, to uncommon repositories, to extensive time investments—becomes potential grist for a future estoppel record. What helps distinguish the petitioner from the examiner at the institution stage can later narrow the gap between the petitioner and Ironburg’s hypothetical “skilled searcher.”

Patent attorneys now need to balance short‑term PTAB gains against long‑term litigation risks. In cases where discretionary denial is a serious concern and estoppel exposure is limited—for example, where the district‑court case is stayed or settlement is likely—leaning into a robust SDD may make sense. In other matters, especially where future district‑court litigation is almost guaranteed and the prior‑art landscape is unsettled, counsel may decide that the marginal benefit of an SDD at the PTAB does not justify the additional estoppel ammunition it hands to the patent owner under Ironburg.

The bottom line is that the “skilled searcher” in § 315(e)(2) is supposed to be hypothetical, and Ironburg gives petitioners room to argue that they are not held to a scorched‑earth standard. The SDD regime invites petitioners to describe, in detail, how they actually search. Bridging that gap may help in the near term at the PTAB, but only if counsel are equally clear‑eyed about how those same disclosures will look when a patent owner later asks a district judge to shut down new invalidity defenses in light of what a skilled searcher, armed with the petitioner’s own methods, reasonably could have found.