Compiled by Citation Safe (Digital Empire Holdings LLC) from the court’s published sanction order (decided October 2, 2026). Quotes and case details come from the order itself — check the primary source before relying on them.

Sanction teardown · E.D. New York, USA · 2026-10-02

Mercante v. Tarzia

What happened

In E.D. New York, USA, a filing relied on Westlaw AI to help draft legal argument. The court identified the following problems with the citations in that filing:

Fabricated (Case Law)

Defense counsel cited a nonexistent case as authority for denying a fee motion. The court confirmed that the case was fictitious, characterized it as an AI hallucination, and held that citing it violated Rule 11.
False Quotes (Case Law)

Defense counsel attributed quoted language concerning willfulness, bad faith, and proportionality of sanctions to a real case, but the quoted language does not appear in the decision. The court found the citation correct and the case generally relevant, but treated the quotation as an apparent misuse of quotation marks rather than clear proof of AI use.
False Quotes (Case Law)

Defense counsel quoted a definition of attorney work product and attributed it to a real case, but the quoted language does not appear in that decision. The court noted that the case does address attorney work-product protection but found no clear indication that AI caused the error.
Misrepresented (Case Law)

Defense counsel cited a real case for a proposition about substantial privacy interests, but the Second Circuit's holding was the opposite: it declined to maintain a permanent seal because privacy interests were weak compared with the presumption of public access. The court treated this as a serious mischaracterization but not conclusive proof of AI use.
Fabricated (Case Law)

Defense counsel cited the correct case name but used an unrelated case's database identifier. The court determined that the real case supported the stated proposition despite the incorrect citation.
Fabricated (Case Law)

Defense counsel cited the correct case name but used an unrelated case's database identifier. The court determined that the real case supported the stated proposition despite the incorrect citation.

Which AI tool

Westlaw AI. 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

Not specified in source record.

Additional detail

Defense counsel admitted using a Westlaw AI tool to identify cases and copying propositions without verifying the authorities or citations. The court found one fictitious case, several false quotations and mis-citations, and at least one materially misrepresented precedent. It held that citing the fictitious case violated Rule 11, but affirmed the magistrate judge's decision not to issue an order to show cause or impose sanctions because Rule 11 sanctions are discretionary, the errors caused no sufficiently demonstrated burden requiring further proceedings, and an admonition was within the court's discretion.

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/3241/Mercante_v._Tarzia_USA_02-10-2026.pdf, via Damien Charlotin's public AI Hallucination Cases Database (CC0).