What was hallucinated

Fabricated: Case Law | Non-existent case; 394 F. Supp. 2d 393 points to a different case (Díaz Rodríguez v. Torres Mártir, 394 F. Supp. 2d 389). Counsel admitted AI use. || Fabricated: Case Law | Non-existent case; KLCE number and WL cite lead to unrelated cases. Counsel attributed to human/Google error. || False Quotes: Case Law | Quoted language not found in the cited case; court noted ConnectU addresses amendment as of right, not prejudice/delay factors. || Misrepresented: Case Law | Case cited for prejudice/delay amendment factors, but it concerns amendment as of right; misstates the case’s holding. || Misrepresented: Case Law | Cited for permitting amendment to add federal claims after finding no diversity, but the case addresses personal jurisdiction and was dismissed. || Misrepresented: Case Law | Cited to support permitting alternative pleadings, but the court did not address or endorse that concept. || False Quotes: Case Law | Quoted language does not exist in the cited decision (WL cite also misstated). Counsel admitted AI use. || False Quotes: Case Law | Quote attributed to Tambone is not in that case; originates from Texas Gulf Sulphur. Counsel admitted AI use. || Fabricated: Case Law | Non-existent case in Westlaw, Lexis, and CM/ECF. Counsel admitted AI use. || False Quotes: Case Law | Quoted proposition not in the cited case. Counsel believed it true generally but conceded mis-citation and AI use. || False Quotes: Case Law | Quoted language not found in the cited Second Circuit case. Counsel admitted AI use.

Details

Plaintiff's counsel in the case of Mintvest Capital, LTD v. NYDIG Trust Company, et al., was found to have included numerous non-existent cases, false quotations, and misrepresented precedents in their filings. The errors were attributed to the use of the AI tool 'Claude' without proper verification. The court recommended sanctions under Rule 11, requiring the attorney to pay the defendants' attorney fees related to the faulty submissions. The court emphasized the need for attorneys to ensure the accuracy of citations, especially when using AI tools, to maintain professional standards.

Sanction teardown · D. Puerto Rico, USA · 2025-06-23

Mintvest Capital, LTD v. NYDIG Trust Company, et al.

What happened

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

Fabricated (Case Law)

Non-existent case; 394 F. Supp. 2d 393 points to a different case (Díaz Rodríguez v. Torres Mártir, 394 F. Supp. 2d 389). Counsel admitted AI use.
Fabricated (Case Law)

Non-existent case; KLCE number and WL cite lead to unrelated cases. Counsel attributed to human/Google error.
False Quotes (Case Law)

Quoted language not found in the cited case; court noted ConnectU addresses amendment as of right, not prejudice/delay factors.
Misrepresented (Case Law)

Case cited for prejudice/delay amendment factors, but it concerns amendment as of right; misstates the case’s holding.
Misrepresented (Case Law)

Cited for permitting amendment to add federal claims after finding no diversity, but the case addresses personal jurisdiction and was dismissed.
Misrepresented (Case Law)

Cited to support permitting alternative pleadings, but the court did not address or endorse that concept.
False Quotes (Case Law)

Quoted language does not exist in the cited decision (WL cite also misstated). Counsel admitted AI use.
False Quotes (Case Law)

Quote attributed to Tambone is not in that case; originates from Texas Gulf Sulphur. Counsel admitted AI use.
Fabricated (Case Law)

Non-existent case in Westlaw, Lexis, and CM/ECF. Counsel admitted AI use.
False Quotes (Case Law)

Quoted proposition not in the cited case. Counsel believed it true generally but conceded mis-citation and AI use.
False Quotes (Case Law)

Quoted language not found in the cited Second Circuit case. Counsel admitted AI use.

Which AI tool

Claude. 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

Order to pay opposing counsel's fees (monetary penalty: 1 USD.)

Additional detail

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.

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Source: https://www.damiencharlotin.com/documents/561/Mintvest_Capital_LTD_v._NYDIG_Trust_Company_et_al_USA_23_June_2025.pdf, via Damien Charlotin's public AI Hallucination Cases Database (CC0).

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