What is an AI-hallucinated citation?
https://citationsafe.com/faq/what-is-an-ai-hallucinated-citation
An AI-hallucinated citation is a citation a generative AI tool produced that does not hold up against a primary source — because the case or statute it names doesn’t exist, because a quotation attributed to a real source never appears in it, or because a real, correctly-cited case doesn’t actually stand for the proposition it’s attached to. The term comes from the broader “AI hallucination” problem: large language models generate the statistically plausible next token, not a fact they looked up, so a citation can read exactly like a real one — correct-looking reporter volume, plausible court and year — while referring to nothing.
The three failure modes
In practice, an AI-hallucinated citation fails in one of three distinct ways, and it matters which one because each requires a different check to catch:
- Existence failure. The case or statute simply does not exist. This is the Mata v. Avianca failure mode — ChatGPT invented six case names, complete with plausible reporter citations, none of which correspond to a real opinion.
- Quote failure. The cited case is real, but the quotation attributed to it never appears in the actual opinion — either fabricated outright or lifted from a different case entirely.
- Proposition failure. The case is real, correctly cited, and the quote is accurate, but the case doesn’t actually support the legal proposition it’s cited for — sometimes because the holding was misread, sometimes because the case was later overruled or distinguished on the exact point being cited.
Existence-only citation checkers catch the first failure mode reliably. They generally do not catch the second or third, which is why a citation can pass a basic “does this case exist” check and still be functionally fabricated in the way that matters to a judge.
Real examples
S.D. New York — decided 2023-06-22 — 5000 USD
Monetary Fine (Lawyers & Firm); Letters to Client/Judges
2nd. Cir. CA — decided 2024-01-30
Referral to Grievance Panel + Order to Disclose Misconduct to Client.
Mata is the existence-failure archetype: six ChatGPT-invented cases, none real. Park v. Kim is a single existence failure in a reply brief that the Second Circuit itself caught while preparing for oral argument — proof that a hallucinated citation doesn’t need to be caught by opposing counsel to end in sanctions.
Why AI tools produce these with such confidence
A generative AI model is not a database lookup. When asked for supporting authority, it produces text that pattern-matches the surface texture of a real citation — plausible party names, a correctly formatted reporter citation, a court and year that fit the fact pattern — because that is what its training optimized it to do. It has no internal notion of “I don’t actually know this case,” and when asked to confirm a citation is real, it will typically just generate another confident-sounding confirmation, which is exactly what happened in the Mata record. That is why verifying a citation by re-asking the same model, or a different model, does not work — see how to check if a case citation exists for what does.
Related resources
- How do I check if a case citation exists?
- What sanctions have courts imposed for AI-hallucinated citations?
- How do you verify a legal citation manually?
- How does Citation Safe compare to other citation-checking tools?
- All FAQ topics
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Written by the Citation Safe Research Desk · Reviewed by Andy Gaber, Founder