AI-hallucinated citations in briefs: how to cite-check before you file
Courts have sanctioned lawyers for AI-invented cases and quotations. A cite-check method that confirms every quotation appears verbatim at the pin cite.
Key takeaways
- In Mata v. Avianca (S.D.N.Y. 2023), lawyers were sanctioned $5,000 for filing a brief citing cases ChatGPT had invented.
- Every citation needs four checks: the authority exists, the quotation is verbatim, the pin cite is right, and the authority supports the proposition.
- AI errors are not only invented cases. Changed words inside a real quotation are harder to spot.
- Keep a record of the cite-check, especially when AI tools were used in drafting.
In 2023, a federal court in New York sanctioned two lawyers and their firm after they filed a brief citing judicial decisions that did not exist. The cases had been generated by ChatGPT. Since then, more courts have dealt with filings containing AI-generated errors, and some judges now require lawyers to disclose or certify their use of generative AI.
The lesson is not to avoid AI tools. It is that the cite-check, always part of good practice, now carries more weight.
What happened in Mata v. Avianca
In Mata v. Avianca, Inc., a personal injury case in the Southern District of New York, the plaintiff's lawyers filed an opposition brief citing several decisions that could not be found. When the court asked for copies, the lawyers relied again on ChatGPT, which confirmed that the cases were real. They were not. In June 2023 the court imposed a $5,000 penalty on the lawyers and their firm.
The invented cases were the headline. The underlying failure was that no one checked the citations against the actual opinions before filing.
The four checks every citation needs
- The authority exists. Pull the opinion itself from a reporter or a legal research database. A citation that cannot be retrieved is not a citation.
- The quotation is verbatim. Every word, including alterations marked with brackets and omissions marked with ellipses.
- The pin cite is right. The quoted language appears on the cited page. Note that the page of a PDF is rarely the page of the reporter.
- The authority supports the proposition. Read the passage in context. A quotation from a dissent, a description of a party's argument, or a rule later rejected does not support the point.
A citator such as Shepard's or KeyCite then confirms that the authority is still good law.
Where AI-assisted drafting goes wrong
- Invented authorities, with plausible names, reporters and pages.
- Real cases, wrong quotations: a sentence that sounds like the court but is not in the opinion.
- Changed words inside a real quotation, such as "shall" for "may", which reverses the meaning.
- Paraphrase presented as a quotation.
- Wrong pin cites, and quotations from headnotes or syllabi rather than the opinion.
The same risks apply to record cites: a quotation from a deposition or an exhibit should be checked against the transcript or document itself.
A quotation check that scales
For a brief with dozens of quotations, the bottleneck is finding each one in the source. A practical workflow:
- Collect every cited opinion, transcript and exhibit as a PDF.
- Extract every quotation from the draft, with its citation.
- Find each quotation in its source, word for word, and confirm the page.
- Flag every difference, however small, and every quotation that cannot be found.
- Read the flagged passages in context, and fix the brief.
How CiteLLM helps with quotation checks
With CiteLLM in ChatGPT or Claude, attach the cited opinions or transcripts, up to 20 PDFs in one review, and paste the quotations from the brief. Each one comes back with the matching passage highlighted on the page. A quotation with changed words is flagged, and one that cannot be found after the whole document has been read is reported as insufficient evidence rather than guessed.
CiteLLM checks quotations against the documents you provide. It does not confirm that a case exists in a reporter or is still good law, so pull every authority yourself and run your citator as usual.
Frequently asked questions
Does CiteLLM replace Shepard's or KeyCite?
No. A citator tells you whether an authority is still good law. CiteLLM confirms that quoted language appears, word for word, in the documents you attach.
Can it check record cites to a deposition transcript?
Yes, if the transcript is a text-based PDF. It finds the passage and its PDF page; confirm the transcript's own page and line numbers on the highlighted page.
Do courts require disclosure of AI use?
Some judges have issued standing orders on generative AI in filings, and practice varies by court. Check the local rules and the judge's individual practices.