CoCounsel, in the Workday AI-bias litigation. A citation stitched together from parts of real ones.
Anthony Hill sued his former employer, Workday. During a discovery fight, Hill's counsel filed a Joint Discovery Letter Brief on July 21, 2025. The brief cited South Pointe Wholesale, Inc. v. Vilardi, 2017 WL 11570668 (E.D.N.Y.), a case that does not exist, and used a parenthetical claiming it acknowledged that "discovery may uncover facts justifying amendments." The brief also misstated the holding of a real case, Mir v. L-3 Communications.
The court flagged the problems and issued an order to show cause. Attorney Katherine Cervantes, who signed the brief, filed a declaration the same day. She first suggested the research tool may have glitched, then at the hearing said the citation was mis-copied. She testified she used Westlaw's CoCounsel and had her paralegal review citations, but admitted she never personally checked the South Pointe citation.
The court found every component of the citation was wrong at once, including party names, docket number, reporter, court, and date. It described the result as a "mashup" bearing the hallmarks of an AI-generated hallucination.
Offered for: supporting authority in the brief
The court publicly admonished Cervantes for violating its AI standing order and Rule 11(b) and for failing to verify the citation. Crediting mitigating factors, including her prompt response and acceptance of responsibility, it declined harsher sanctions but ordered her to circulate the orders firm-wide and complete at least four hours of in-person CLE covering staff supervision, ethics, and AI use. Attorney Lenden Webb, whose name was also on the brief, did not appear; the court admonished him and ordered him to file a declaration within fourteen days. The order to show cause was not discharged as to Webb.
Kingsfield returned REJECT. A 'mashup' citation that matches no real opinion. The court treated it as an AI fabrication and faulted counsel for not verifying it.
This matter is among the US case-law cases we ran Kingsfield against in the Charlotin benchmark. Kingsfield's existence check confirms every citation against the case-law corpus and an independent source (CourtListener) before any claim resting on it can stand. Across the run Kingsfield ruled 696 of 700 testable claims correctly, including every one of the 504 fabricated citations and 92 fabricated quotes.
Honest scope. This measures Kingsfield's ruling layer given an extracted citation, not an end-to-end run over a full brief. The case record and the AI-tool attribution come from Damien Charlotin's public database and the court order; the verdict is Kingsfield's. See the full 700-claim benchmark.