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 the AI produced hallucinated content. 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 (3 cases identified so far), 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 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.)

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State
Party
Nature – Category
Nature – Subcategory

Case Court / Jurisdiction Date ▼ Party Using AI AI Tool Nature of Hallucination Outcome / Sanction Monetary Penalty Details
Malone & Anor v Laois County Council & Ors High Court (Ireland) 23 June 2025 Pro Se Litigant Implied
Fabricated Legal Norm (1)
False Quotes Case Law (1)
Misrepresented Exhibits or Submissions (1), Legal Norm (1)
Warning —

Referring to Ayinde, the judge held that "The principle is essentially the same - though I hasten to say that I would not push the analogy too far as to a factual comparison of the present case with that case and the error in the present case is not of the order of the misconduct in that case. However, appreciable judicial time was wasted on the issue - not least trying to find the source of the quotation. And it does illustrate:

  • The vital importance of precision and accuracy in written submissions. That duty lies on lay litigants as much as on lawyers.
  • That text in submissions formatted so as to convey that it is a direct and verbatim quotation from an identified source must be exactly that. Of course, it is permissible to edit the text (for example to exclude irrelevant content or by underlining for emphasis) but, if so, that it has been done must be apparent on the face of the document.
  • That opposing parties are entitled to written submissions in good time to check them.

43. All that said, in a substantive sense, the issue is not vital to this case. The underlying proposition for which Mr Malone contends - that domestic courts must implement EU law - is uncontroversial. Not least for that reason, and in light also of the manner in which Mr Malone generally presented his case at the hearing, I am inclined to accept that there was no attempt or intention to mislead and accept also that Mr Malone has apologized for the error. It does not affect the outcome of the present motions."
Reddan & An Bord Pleanála v. Trustees of Nenagh Golf Club (Ireland) 13 March 2025 Pro Se Litigant Unidentified
Fabricated Exhibits or Submissions (1), other (1)
Misrepresented Legal Norm (4), other (1)
Application for Judicial Review Denied; Express Judicial Rebuke for Misuse of AI —

AI Use

Justice Nolan suspected that Reddan's submissions, especially references to "subornation to perjury" and Constitutional Article 40 rights, were AI-generated, exhibiting typical hallucination patterns (pseudo-legal concepts, inappropriate cut-and-paste fragments). Reddan did not admit using AI but relied on internet-sourced legal arguments that closely resembled LLM-style outputs.

Hallucination Details

Inappropriate invocation of "subornation to perjury," a term foreign to Irish law. Constitutional and criminal law citations (Article 40, Non-Fatal Offences Against the Person Act) irrelevant to judicial review context. Assertions framed in hyperbolic, sensationalist terms without factual or legal basis. General incoherence of pleadings, consistent with AI-generated pseudo-legal text

Ruling/Sanction

The High Court refused leave to apply for judicial review on all nine grounds. While no formal financial sanction was imposed, Justice Nolan issued a sharp rebuke, highlighting the improper use of AI and warning against making scurrilous, unverified allegations in legal pleadings. The Court stressed that misuse of AI-generated material could itself amount to an abuse of the judicial process.
John Coulsto et al. v Elliott The High Court (Ireland) 10 December 2024 Pro Se Litigant implied
Outdated Advice Repealed Law (1)
Court rejected the submission as fallacious —

Defendants' written submissions (not argued at trial) advanced that s.19 of the Conveyancing Act 1881 had been repealed by the 2009 Act, undermining the power to appoint a receiver. The court found the argument fallacious, noted s.19 was reinstated by the 2013 Act, and observed the submissions were likely produced by a generative AI or an unqualified adviser.