Prososki v. Regan: Filing Fictitious (Including AI-“Hallucinated”) Authority Warrants Striking the Brief, Dismissing the Appeal, and Disciplinary Referral Under Existing Candor/Competence Rules

1. Introduction

Prososki v. Regan, 321 Neb. 38 (Mar. 20, 2026), arose from a Douglas County decree dissolving the marriage of Jennifer M. Prososki (appellee/cross-appellant) and Jason C. Regan (appellant/cross-appellee). The merits issues typical of dissolution litigation—custody/parenting time, child support, and property division—were overtaken on appeal by an issue the Nebraska Supreme Court described as “novel” for Nebraska courts: an appellant’s brief containing numerous fictitious or inaccurate citations, fabricated quotations, and misstatements of legal authority, which the appellee asserted were generated by generative AI.

The case therefore presented two intertwined questions: (1) how the appellate court should respond to a brief “riddled” with fabricated authority and quotations (from both cases and statutes/rules), and (2) whether any reversible error existed on the cross-appeal regarding inclusion of real estate in the marital estate when evidence necessary to apply Nebraska’s “source of funds” methodology was missing.

2. Summary of the Opinion

The Nebraska Supreme Court held that submission of fictitious authority—whether produced by generative AI or otherwise—is addressable under existing Nebraska Rules of Professional Conduct and court rules. As sanctions, the Court:

  • Struck Jason’s appellate brief,
  • Dismissed Jason’s appeal, and
  • Referred Jason’s counsel to the Counsel for Discipline.

Despite the dismissal, the Court exercised discretion to review the appellant’s assignments for plain error and found none. On Jennifer’s cross-appeal, the Court affirmed the district court’s property classification, concluding the evidence was insufficient to establish any marital interest in Jason’s premarital duplex under Stava v. Stava because the record lacked proof of mortgage history, principal reduction, and reliable valuation at the relevant date—making any computation speculative.

3. Analysis

A. Precedents Cited

1) Appellate briefing noncompliance and plain-error review

  • Swicord v. Police Stds. Adv. Council, 309 Neb. 43, 958 N.W.2d 388 (2021): Cited for the principle that when a brief fails to comply with Neb. Ct. R. App. P. § 2-109(D)(1)(e), the appellate court may treat the party as having failed to file a brief or may review for plain error. The Court used this framework as the procedural gateway to impose sanctions while still checking the record for plain error.
  • Seivert v. Alli, 309 Neb. 246, 959 N.W.2d 777 (2021): Cited for de novo review on the record and the weight given to the trial court’s credibility determinations when evidence conflicts—important context for the cross-appeal’s evidentiary shortcomings.
  • Seemann v. Seemann, 316 Neb. 671, 6 N.W.3d 502 (2024): Cited for the proposition that the weight of expert testimony is for the fact finder, reinforcing that valuation disputes (if properly supported) are not mechanically retried on appeal.
  • Simons v. Simons, 312 Neb. 136, 978 N.W.2d 121 (2022): Cited for the rule that appellate courts generally do not consider arguments raised for the first time on appeal; later used to note Jennifer did not pursue discovery enforcement below and did not assign discovery error on appeal.

2) Property classification and the “source of funds” methodology

  • Stava v. Stava, 318 Neb. 32, 13 N.W.3d 184 (2024): The central property precedent. The Court relied on Stava to restate: (i) property may have mixed marital/nonmarital components; (ii) premarital equity is separate; (iii) marital payments reducing principal on premarital encumbered property can create a marital interest; and (iv) Stava’s formula requires evidence of value at division and the marital and total contributions to equity. Prososki’s cross-appeal failed because the record did not provide these inputs.
  • Estate of Block v. Estate of Becker, 313 Neb. 818, 986 N.W.2d 726 (2023): Cited for the evidentiary axiom that findings cannot rest on “guess, speculation, or conjecture,” which became dispositive against Jennifer’s proposed calculation based on incomplete data.

3) Professional conduct—candor, competence, and dishonesty standards

  • State ex rel. Counsel for Dis. v. Pearson, 310 Neb. 256, 965 N.W.2d 28 (2021); State ex rel. Counsel for Dis. v. Schmidt, 303 Neb. 755, 930 N.W.2d 577 (2019); State ex rel. Counsel for Dis. v. Bouda, 278 Neb. 380, 770 N.W.2d 648 (2009): These disciplinary cases grounded the Court’s discussion of the duty of candor and the kinds of misrepresentations that implicate professional discipline (false statements in pleadings, misrepresenting party approval, misrepresenting settlement authority).
  • State ex rel. Counsel for Dis. v. Hanson, 305 Neb. 566, 941 N.W.2d 193 (2020): Used for a key mens rea clarification: proof of actual intent is not required under misconduct involving “dishonesty, fraud, deceit, or misrepresentation”; the inquiry focuses on the effect of the conduct. This supports sanctioning even when counsel claims inadvertence or tool error.
  • State ex rel. Counsel for Dis. v. Glass, 320 Neb. 201, 26 N.W.3d 538 (2025): Cited for the proposition that violations of the Rules of Professional Conduct are grounds for discipline under the Court’s exclusive jurisdiction.
  • White v. White, 320 Neb. 256, 26 N.W.3d 924 (2025): Cited for language describing arguments “so wholly without merit as to be ridiculous,” reinforcing the Court’s characterization of briefs supported by fabricated law.

4) Sanctions and inherent authority (including out-of-jurisdiction persuasive authority)

  • Mata v. Avianca, Inc., 678 F. Supp. 3d 443 (S.D.N.Y. 2023): Persuasive authority illustrating sanctions for citing nonexistent cases and emphasizing the “gatekeeping role” attorneys have to ensure accuracy—used by the Court to anchor its conclusion that existing rules suffice to address AI-related hallucinations.
  • Pillay v. I.N.S., 45 F.3d 14 (2d Cir. 1995): Cited for the proposition that an appellate court has inherent authority to dismiss a frivolous appeal.

5) Concurrence’s sanctions landscape (comparative references)

Justice Stacy’s concurrence canvassed additional authorities showing the range of sanctions used elsewhere for fabricated authority: Park v. Kim, 91 F.4th 610 (2d Cir. 2024); Grant v. City of Long Beach, 96 F.4th 1255 (9th Cir. 2024); Kruse v. Karlen, 692 S.W.3d 43 (Mo. App. 2024); and others, while also citing Nebraska inherent-power authority, Houser v. American Paving Asphalt, 299 Neb. 1, 907 N.W.2d 16 (2018), and briefing-compliance precedent, Kellogg v. Mathiesen, 320 Neb. 223, 26 N.W.3d 651 (2025). The concurrence further noted In re Estate of Marsh, 145 Neb. 559, 17 N.W.2d 471 (1945), for the proposition that dismissal of an appeal generally operates as affirmance—supporting the concurrence’s preference to affirm (after plain-error review) rather than dismiss.

B. Legal Reasoning

1) The new operational rule: fictitious authority is sanctionable under existing Nebraska doctrine

The Court’s core doctrinal move was to reject the need for “AI-specific” procedural innovations as a prerequisite to enforcement. It held that submission of fictitious authority—“whether through generative AI or not”—is resolvable through established duties:

  • Candor to the tribunal (Neb. Ct. R. of Prof. Cond. § 3-503.3(a)(1)): lawyers must not make false statements of law or fail to correct them. The Court accepted that “conscious avoidance” or inadequate verification can satisfy the “knowingly” component, and it found an additional breach in counsel’s delayed attempt to correct only after being confronted by the motion to strike.
  • Competence (§ 3-501.1): competent representation requires thoroughness and awareness of the benefits and risks of technology (comment 6). The Court treated basic verification (Westlaw/Lexis, official sources, or the free Nebraska Appellate Courts Online Library) as an expected minimum.
  • Diligence (§ 3-501.3) and nonfrivolous contentions (§ 3-503.1): fake authority cannot be “existing law” and thus cannot supply a nonfrivolous basis for relief.
  • Misconduct involving dishonesty/misrepresentation (§ 3-508.4(c)): relying on State ex rel. Counsel for Dis. v. Hanson, the Court emphasized that actual intent is not required; the effect of the conduct is sufficient.

2) Sanction selection: striking the brief + dismissing the appeal + disciplinary referral

The Court framed the fabricated citations and quotations as a “serious dereliction” undermining the judicial process. Given the breadth of the defects (including fabricated quotations from statutes and court rules), it exercised inherent authority to strike the brief and dismiss the appeal, and it referred counsel to the Counsel for Discipline. The Court explicitly left open Jennifer’s ability to seek attorney fees, signaling that dismissal did not necessarily exhaust remedial consequences.

3) Plain error review as a fairness backstop to the litigant

Although the Court found the appeal “entirely meritless” as presented, it nevertheless reviewed the assignments for plain error “in fairness to Jason.” This is a notable procedural posture: the Court protected institutional integrity through sanctions while attempting to mitigate the risk that the client would be punished for counsel’s briefing misconduct beyond the dismissal itself. It found no plain error.

4) Cross-appeal: applying Stava requires evidence, not estimation

On Jennifer’s cross-appeal, the Court applied Stava v. Stava to reiterate that a marital interest can arise when marital funds pay down principal on premarital encumbered property, and that appreciation in the marital interest is marital. But it refused to manufacture the missing data. Because the record lacked (i) reliable 2016 valuation, (ii) mortgage origination terms and balances at relevant times, and (iii) evidence of principal reduction attributable to marital funds during the 2012–2016 period, any attempt to compute a marital share would be speculative under Estate of Block v. Estate of Becker. The Court also noted Jennifer did not pursue discovery enforcement below and did not assign discovery error on appeal, limiting appellate remedies.

C. Impact

1) Nebraska’s first explicit AI-hallucination appellate discipline framework—without new rules

Prososki functions as Nebraska’s foundational precedent for handling fabricated authority in filings, including those plausibly generated by AI. The Court’s key practical message is that the source of the fabrication (AI, clerical error, or otherwise) does not alter the attorney’s verification duty or the availability of sanctions. This likely increases:

  • Verification expectations (cite-checking and quotation checking) as a minimum competency requirement;
  • Sanction risk for “conscious avoidance” of verification and for delayed correction after notice;
  • Disciplinary exposure even absent proven intent to deceive, because the effect on the tribunal is central.

2) Appellate practice consequences

The remedy chosen—striking the brief and dismissing the appeal—signals that systemic fabrication may be treated as a structural assault on appellate adjudication. Litigants may increasingly seek early motions to strike where fabricated authority is suspected, and courts may more readily order show-cause proceedings, referrals, or fee-shifting.

3) Property division: Stava’s evidentiary prerequisites

The cross-appeal portion reinforces that Stava is powerful but data-dependent. Parties seeking to prove a marital interest in premarital encumbered real estate must develop the mortgage timeline, principal reduction amounts, and reliable valuation evidence; otherwise the claim fails as speculative even if the general legal theory is sound.

4. Complex Concepts Simplified

  • “Hallucinations” (generative AI): outputs that look like plausible legal citations or quotations but are invented or inaccurately attributed. The Court treated them as ordinary falsities for sanction purposes.
  • Duty of candor to the tribunal: the lawyer’s obligation not to mislead the court—especially by citing fake cases, fake quotations, or misstating holdings—and to correct errors once discovered.
  • Plain error: a clear, obvious error in the record that threatens the fairness or integrity of the process and can be corrected even when briefing is deficient.
  • “Source of funds” rule (Stava): ownership classification tracks who paid for the property’s equity. If marital funds paid down principal on a premarital mortgage, the marital estate may gain a proportional interest (including passive appreciation on that marital share).
  • Passive vs. active appreciation: passive appreciation is market-driven; active appreciation results from effort/improvement. Prososki reiterates that appreciation in the marital interest is marital, but premarital equity (and its passive appreciation) remains separate if established.
  • Speculation is not proof: courts cannot assign numeric values or shares without evidence; they cannot choose among “quantitative possibilities” without a factual basis.

5. Conclusion

Prososki v. Regan establishes Nebraska’s first clear appellate response to briefs supported by fabricated legal authority: existing rules of candor, competence, diligence, nonfrivolous advocacy, and misconduct are sufficient to sanction the submission of fictitious citations and quotations, including those associated with generative AI. The Court’s chosen sanctions—striking the brief, dismissing the appeal, and referring counsel for discipline—underscore that accuracy in legal authorities is not a stylistic preference but a structural requirement of adjudication.

On the merits-adjacent cross-appeal, the opinion also serves as a practical evidentiary reminder: Stava v. Stava can expand the marital estate through mortgage principal reduction and appreciation, but only where the record supplies the necessary valuation and mortgage data. Without that proof, courts will not speculate.