What was hallucinated

Fabricated: Case Law | Plaintiff cited a non-existent case; the court confirmed no such case exists. || Misrepresented: Case Law | Plaintiff cited an existing case with an incorrect reporter citation; the cited volume/page corresponds to a different N.D. Cal. case, and it is unclear which Equifax case was intended.

Details

AI UseWhile not formally admitted, Plaintiff’s opposition brief referred to “legal generative AI program CoCounsel,” and the court noted that the structure and citation pattern were consistent with AI-generated output. Capital One was unable to verify several case citations, prompting the court to scrutinize the submission.Hallucination DetailsAt least one case was fully fabricated, and another was a real case misattributed to the wrong jurisdiction and reporter. The court emphasized that it could not determine whether the mis-citations were the result of confusion, poor research, or hallucinated AI output—but the burden rested with the party filing them.Ruling/SanctionThe court dismissed the complaint with prejudice, noting Plaintiff had already filed and withdrawn a prior version and had had full opportunity to amend. Though it did not impose monetary sanctions, it issued a strong warning and directed Plaintiff to notify other courts where he had similar pending cases if any filings included erroneous AI-generated citations.

Sanction teardown · D. DC, USA · 2025-03-18

Williams v. Capital One Bank

What happened

In D. DC, USA, a filing relied on CoCounsel to help draft legal argument. The court identified the following problems with the citations in that filing:

Fabricated (Case Law)

Plaintiff cited a non-existent case; the court confirmed no such case exists.
Misrepresented (Case Law)

Plaintiff cited an existing case with an incorrect reporter citation; the cited volume/page corresponds to a different N.D. Cal. case, and it is unclear which Equifax case was intended.

Which AI tool

CoCounsel. Note: Charlotin's public database records tool attribution only where a court order, brief, or reporting on the matter states it explicitly; "unidentified" or "implied" means the record indicates AI use but does not name a specific product — we do not guess.

Outcome

Case dismissed with prejudice for failure to state a claim. No monetary sanction imposed, but the court issued a formal warning

Additional detail

AI UseWhile not formally admitted, Plaintiff’s opposition brief referred to “legal generative AI program CoCounsel,” and the court noted that the structure and citation pattern were consistent with AI-generated output. Capital One was unable to verify several case citations, prompting the court to scrutinize the submission.Hallucination DetailsAt least one case was fully fabricated, and another was a real case misattributed to the wrong jurisdiction and reporter. The court emphasized that it could not determine whether the mis-citations were the result of confusion, poor research, or hallucinated AI output—but the burden rested with the party filing them.Ruling/SanctionThe court dismissed the complaint with prejudice, noting Plaintiff had already filed and withdrawn a prior version and had had full opportunity to amend. Though it did not impose monetary sanctions, it issued a strong warning and directed Plaintiff to notify other courts where he had similar pending cases if any filings included erroneous AI-generated citations.

How Citation Safe would have caught this

Citation Safe runs three deterministic layers before a brief is filed: (1) does the citation exist against CourtListener's database of published opinions, (2) if quoted, does that exact language appear in the source, (3) does the cited case actually support the proposition it is cited for. Fabricated case citations fail Layer 1. Fabricated or misattributed quotations fail Layer 2 even when the underlying case is real. Misrepresented holdings — a real case cited for a proposition it does not support — are the target of Layer 3. None of these checks involve asking another language model whether the citation looks right; they are lookups and text-matches against the actual source, which is why a hallucinated citation has to survive a direct lookup against the authoritative source — not another model's opinion — to earn a VERIFIED stamp; our measured false-verify rate is published live at /quality.

Check a brief before you file it → · See our live false-verify rate

Source: https://www.damiencharlotin.com/documents/362/Williams_v._Capital_One_Bank_N.A._D._D.C._March_18_2025.pdf, via Damien Charlotin's public AI Hallucination Cases Database (CC0).