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 (6 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 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: 19 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)
Caso No. 0000140/2025-00 TSJ Gran Canaria (Spain) (Spain) 10 February 2026 Lawyer Unidentified
Fabricated Case Law (1), Legal Norm (1), other (1)
False Quotes Case Law (2)
Misrepresented Case Law (1)
Monetary Sanction; Bar Referral 420 EUR
Sentencia 000126/2025 TSJ Gran Canaria (Spain) 31 December 2025 Lawyer Implied
Fabricated Case Law (1), Doctrinal Work (1)
False Quotes Case Law (2)
Misrepresented other (1)
Unknown criminal case Ceuta (Spain) 1 December 2025 Judge, Prosecutor Implied
Fabricated Case Law (1)

See here for details.

⚠ Alleged AI Use
SAP A 1558/2025 - ECLI:ES:APA:2025:1558 AP Alicante (Spain) 8 October 2025 Lawyer Implied
False Quotes Case Law (1)
Bar referral
Anonymous Spanish Lawyer Tribunal Constitucional (Spain) 9 September 2024 Lawyer Unidentified 19 fabricated Constitutional Court decisions Formal Reprimand (Apercibimiento) + Referral to Barcelona Bar for Disciplinary Action

AI Use

The Court noted that the false citations could stem from AI, disorganized database use, or invention. Counsel claimed a database error but provided no evidence. The Court found the origin irrelevant: verification duty lies with the submitting lawyer.

Hallucination Details

Nineteen separate fabricated citations to fictional Constitutional Court judgments. Fake quotations falsely attributed to those nonexistent decisions. Cited to falsely bolster claims of constitutional relevance in an amparo.

Ruling/Sanction

The Constitutional Court unanimously found that the inclusion of nineteen fabricated citations constituted a breach of the respect owed to the Court and its judges under Article 553.1 of the Spanish Organic Law of the Judiciary. Issued a formal warning (apercibimiento) rather than a fine due to absence of prior offenses. Referred the matter to the Barcelona Bar for possible disciplinary proceedings

Key Judicial Reasoning

The Court stressed that even absent express insults, fabricating authority gravely disrespects the judiciary’s function. Irrespective of whether AI was used or a database error occurred, the professional duty of diligent verification was breached. The Court noted that fake citations disrupt the court’s work both procedurally and institutionally.

ATSJ NA 38/2024 TSJ Navarra (Spain) 4 September 2024 Lawyer CHATGPT 3
Fabricated Legal Norm (1)