AI Hallucination Cases

"In her declaration, Attorney Cervantes described the erroneous citation as her own inadvertent error and further implied that Westlaw’s tool may have “glitched” by erroneously producing the citation. [Dkt. 31 at ¶ 4]. Specifically, she indicates that the copy citation tool mayhave inadvertently copied the wrong citation information.

Yet, that explanation seems highly improbable. The citation was incorrect in every respect and none of the sub-parts of the citation match each other, including the case docket number, reporter, pincite, court information, and date information. The likelihood of every component of a citation being simultaneously wrong due to a software malfunction in transcribing from a “correct” citation is, in the Court’s view, statistically improbable (particularly given Westlaw’s representations as to the accuracy of its tools and the apparent resources Westlaw has devoted to promoting the reputation of this tool). If one set of numbers had been transposed, or if the date were wrong, such transcription errors might be explicable. However, the fact that the party names, docket number, Westlaw citation, date, and court all failed to match, resulting in a mashup citation, cannot credibly be attributed to a software error, let alone a mistranscription or copying mistake. Rather,this Frankensteinian legal citation, stitched together from mismatched party names, docket numbers, dates, and courts, bears the hallmarks of an AI-generated hallucination, as documented in numerous published opinions and reports."

AI Use

Counsel used CoCounsel, Westlaw’s AI tools, and Google Gemini to generate a legal outline for a discovery-related supplemental brief. The outline contained hallucinated citations and quotations, which were incorporated into the filed brief by colleagues at both Ellis George and K&L Gates. No one verified the content before filing. After the Special Master flagged two issues, counsel refiled a revised brief—but it still included six AI-generated hallucinations and did not disclose AI use until ordered to respond.

Hallucination Details

At least two cases did not exist at all, including a fabricated quotation attributed to Booth v. Allstate Ins. Co., 198 Cal.App.3d 1357 (1989). Misquoted or fabricated quotes attributed to National Steel Products Co. v. Superior Court, 164 Cal.App.3d 476 (1985). Several additional misquotes and garbled citations across three submitted versions of the brief. Revised versions attempted to silently “fix” errors without disclosing their origin in AI output.

Ruling/Sanction

The Special Master (Judge Wilner) struck all versions of Plaintiff’s supplemental brief, denied the requested discovery relief, and imposed:

• $26,100 in fees to reimburse Defendant for Special Master costs
• $5,000 in additional attorney’s fees to Defendant
• Total monetary sanction: $31,100, payable jointly and severally by Ellis George LLP and K&L Gates LLP
• No sanctions against individual attorneys due to candid admissions and remedial action, but strong warning issued

Key Judicial Reasoning

The submission and re-submission of AI-generated material without verification, especially after warning signs were raised, was deemed reckless and improper. The court emphasized that undisclosed AI use that results in fabricated law undermines judicial integrity. While individual attorneys were spared, the firms were sanctioned for systemic failure in verification and supervision. The Special Master underscored that the materials nearly made it into a judicial order, calling that prospect “scary” and demanding “strong deterrence.”

AI Use

While 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 Details

At 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/Sanction

The 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.