AI Hallucination Cases

This database tracks legal decisions1 I.e., all documents where the use of AI, whether established or merely alleged, is addressed in more than a passing reference by the court or tribunal.

Notably, this does not cover mere allegations of hallucinations, but only cases where the court or tribunal has explicitly found (or implied) that a party relied on hallucinated content or material.

As an exception, the database also covers some judicial decisions where AI use was alleged but not confirmed. This is a judgment call on my part. in cases where generative AI produced hallucinated content – typically fake citations, but also other types of AI-generated arguments. It does not track the (necessarily wider) universe of all fake citations or use of AI in court filings.

While seeking to be exhaustive (54 cases matching search), it is a work in progress and will expand as new examples emerge. This database has been featured in news media, and indeed in several decisions dealing with hallucinated material.2 Examples of media coverage include:
- M. Hiltzik, AI 'hallucinations' are a growing problem for the legal profession (LA Times, 22 May 2025)
- E. Volokh, "AI Hallucination Cases," from Courts All Over the World (Volokh Conspiracy, 18 May 2025)
- J-.M. Manach, "Il génère des plaidoiries par IA, et en recense 160 ayant « halluciné » depuis 2023" (Next, 1 July 2025) - J. Koebler & J. Roscoe, "18 Lawyers Caught Using AI Explain Why They Did It (404 Media, 30 September 2025)

If you have any questions about the database, a FAQ is available here.
And if you know of a case that should be included, feel free to contact me.3 (Readers may also be interested in this project regarding AI use in academic papers.)

Based on this database, I have developed an automated reference checker that also detects hallucinations: PelAIkan. Check the Reports Report icon in the database for examples, and reach out to me for a demo.

For weekly takes on cases like these, and what they mean for legal practice, subscribe to Artificial Authority.

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Last updated: 31 May 2026
State
Party
Nature – Category
Nature – Subcategory

Case Court / Jurisdiction Date ▼ Party Using AI AI Tool ⓘ Nature of Hallucination Outcome / Sanction Monetary Penalty Details Report(s)
In re Thomas Grant Neusom M.D. Florida (USA) 8 May 2025 Lawyer Unidentified Multiple fictitious or misrepresented case citations Suspension from practice before the Middle District of Florida for one year; immediate prohibition on accepting new federal matters; conditional reinstatement — —

(Grievance Committee Report available here.)

AI Use

Neusom told the grievance committee that he “may have used artificial intelligence” in preparing filings, and that any hallucinated cases were not deliberately fabricated but may have come from AI tools. The filings in question included a notice of removal and a motion for summary judgment. The judge later noted a pattern of citations inconsistent with established case law and unsupported by known databases.

Hallucination Details

Citations included cases that either did not exist or were grossly mischaracterized. Notably:

  • Southern Specialties, Inc. v. Pulido Produce, Inc. – no such case found in Westlaw, Lexis, or PACER
  • Trilogy Communications v. Times Fiber – cited in support of breach of contract when it was a patent matter involving no such principles

Neusom failed to produce the full texts of the cited cases when requested and instead filed a 721-page exhibit in violation of court orders.

Ruling/Sanction

The court adopted the grievance committee’s recommendation and imposed a one-year suspension. Neusom is prohibited from accepting new federal cases in the Middle District of Florida during the suspension and must:

  • Notify existing clients and the court of his suspension
  • File a compliance affidavit within 30 days
  • Complete appropriate CLE and counseling programs
  • Remain in good standing with the Florida Bar
  • Apply for reinstatement only after certifying compliance

Key Judicial Reasoning

The court found that Neusom violated Rules 4-1.3, 4-3.3(a)(3), 4-3.4(c), and 4-8.4(c) of the Florida Rules of Professional Conduct. His failure to verify AI-generated content, compounded by noncompliance with orders and false statements to opposing counsel, demonstrated a pattern of recklessness and dishonesty. The court emphasized that federal proceedings require a high standard of diligence and that invoking AI cannot excuse failure to meet professional obligations.
Sheets v. Presseller M.D. Florida (USA) 11 March 2025 Pro Se Litigant Implied Allegations by the other party that brief was AI-generated Warning — —
O’Brien v. Flick and Chamberlain S.D. Florida (USA) 10 January 2025 Pro Se Litigant Implied
Fabricated Case Law (2)
Case dismissed with prejudice, inter alia for use of fake citations and misrepresentations — —

AI Use

Although O’Brien denied deliberate fabrication and described the inclusion of fake citations as a “minor clerical error” or “mix-up,” the court rejected this explanation. The opinion notes that the citations had no plausible source in other filings and that the brief exhibited structural traits of AI-generated text. The court explicitly concluded that O’Brien “generated his Reply with the assistance of a generative artificial intelligence program.”

Ruling/Sanction

The court dismissed the case with prejudice on dual grounds:

  • The claims should have been raised as compulsory counterclaims in prior pending litigation and were thus procedurally barred under Rule 13(a)
  • O’Brien submitted fake legal citations, failed to acknowledge the issue candidly, violated local rules, and engaged in a pattern of procedural misconduct in this and other related litigation. While monetary sanctions were not imposed, the court granted the motion to strike and ordered dismissal with prejudice as both substantive and disciplinary remedy.

Key Judicial Reasoning

Judge Melissa Damian found that the fabricated citations and O’Brien’s refusal to admit or correct them constituted bad faith. She referenced multiple prior instances where O’Brien had been warned or sanctioned for similar behavior, and emphasized that while pro se litigants may receive procedural leniency, they are not exempt from ethical or legal standards. Dismissal with prejudice was chosen as a proportionate sanction under the court’s inherent powers.
Carlos E. Gutierrez v. In Re Noemi D. Gutierrez Fl. 3rd District CA (USA) 4 December 2024 Pro Se Litigant Unidentified
Fabricated Case Law (1)
False Quotes Case Law (1)
Appeals dismissed as sanction; Appellant barred from future pro se filings in related probate matters without attorney signature — —

AI Use

The court did not specify how the hallucinated material was generated but described the bulk of appellant’s cited cases as “phantom case law.”

Hallucination Details

The court identified that the “Augmented Appendix Sections” attached to each brief consisted of numerous nonexistent Florida cases. Some real cases were cited, but quotes attributed to them were fabricated.

Ruling/Sanction

Dismissal of both consolidated appeals as a sanction. Bar on further pro se filings in the underlying probate actions without review and signature of a Florida-barred attorney. Clerk directed to reject noncompliant future filings

Key Judicial Reasoning

The Court held that Gutierrez’s submission of fictitious legal authorities and failure to respond to the show cause order constituted an abuse of process. It emphasized that pro se litigants are bound by the same rules as attorneys and referenced prior sanctions cases involving AI hallucinations.