Who's Submitting AI-Tainted Filings in Court?

Source: Riana Pfefferkorn, Stanford Center for Internet and Society · 2025-10-15

It seems like every day brings another news story about a lawyer caught unwittingly submitting a court filing that cites nonexistent cases hallucinated by AI. The problem persists despite courts’ standing orders on the use of AI, formal opinions and continuing legal education (CLE) courses on ethical use of AI in law practice, and revelations that AI-powered legal research tools are more fallible than they purport to be.

Who are the attorneys submitting AI-tainted briefs? A recent 404 Media article about lawyers’ use of AI drew my attention to a database of AI Hallucination Cases compiled and maintained by Damien Charlotin, a French lawyer and scholar. Charlotin classifies the nature of the incident by various types of inaccuracies: fabricated cases, false quotes from or misrepresentations of real cases, or outdated invocations of cases that have been overturned. Besides helping the public understand how lawyers are getting tripped up by AI, Charlotin’s database also enables a better view of who is getting tripped up by AI.

Using the database, I analyzed 114 cases from U.S. courts where, according to either opposing counsel and/or the court’s own investigation, an attorney’s filing included inaccuracies that were suspected or shown to have been caused by the use of AI. I find that the vast majority of the law firms involved – 90% – are either solo practices or small firms. What’s more, in 56% of the cases, the AI hallucinations were attributed to the plaintiff’s counsel, compared with 31% to the defense. And, while most cases in the sample did not specify the AI tool used, of those that did, fully half involved some version of ChatGPT.

I based my analysis on cases I downloaded in a .csv file from Charlotin’s database on October 9, 2025. The time period covers court orders issued from June 2023 (the month of the landmark order in Mata v. Avianca) through October 7, 2025.

[Note: October 9 was a Thursday; by the following Monday, when I began drafting this write-up, Charlotin had added three new matters involving pro se litigants (which I exclude from my analysis) as well as two updates on cases that were already in the database (and thus already in my sample), plus there was news coverage of an oral argument where an attorney was grilled about hallucinations in his briefing. I did not add that last matter, which had not yet yielded a written opinion at the time I wrote this, to my sample.

There may be errors in my data, thanks to having to guess about some things (such as whether someone is a solo practitioner) or relying on inaccurate or outdated sources (for example, third-party reporting on firm size). If you find an error, please email me (riana at stanford dot edu) and I’ll fix it and update this post.

The plaintiff is more commonly the party allegedly responsible for submitting filings containing AI hallucinations. Out of 114 cases, 64 were attributed to the plaintiff (56.1%), compared with 35 to the defendant (30.7%). There were 15 “other” cases (13.2%): bankruptcy, family, probate, and tax court matters, agency matters, a habeas petition, and an attorney disciplinary proceeding. (The lawyer allegedly submitted filings with AI hallucinations during that disciplinary proceeding, not in an underlying case involving that lawyer like other disciplinary proceedings in the sample. Where the attorney was facing discipline for misusing AI while representing a client, I classified the lawyer according to the party they were representing in the underlying case.)

Solo practices and small firms represent the overwhelming majority of that number. Solos account for half (50.4%) and small firms of 2-25 lawyers for another 39.5%. Of the remaining 10% of firms, 3.1% are firms of 26-100 lawyers; 2.3% are firms of 201-500 lawyers; 1.6% are firms of 1001+ attorneys; 1.6% are government entities; and firms of either 101-200 or 501-700 lawyers each represent less than 1%. There were no cases involving firms of 701-1000 lawyers.

The number of firms in the sample with more than 25 lawyers is small enough to count on two AI-generated hands. Four have up to 100 lawyers: Ellis George, Hagens Berman Sobol Shapiro, Merlin Law Group, and Williams Kastner. Five have 101-700 lawyers: Butler Snow, Goldberg Segalla, Morrison Mahoney, Quintairos Prieto Wood & Boyer, and Spencer Fane. Two have more than 1000 attorneys: K&L Gates and Morgan & Morgan.

Five lawyers are implicated in more than one case in the sample. All are either solo practitioners or small-firm lawyers: solo Maren Miller Bam of Salus Law; Jane Watson of Watson & Norris (who was only admitted to the bar in 2024); Chris Kachouroff of McSweeney Cynkar & Kachouroff (who gained notoriety for appearing pantsless at a Zoom court hearing); solo Tyrone Blackburn (who got arrested for assault in June in connection with a different case of his); and William Panichi, a family-court attorney. While the first four allegedly misused AI in two separate cases, Panichi was called out in an astonishing four cases in one 30-day period; he has supposedly begun winding down his law practice and surrendering his license.

Of the 114 cases in the sample, only 34 (30%) identified the specific AI tool(s) used by the attorneys. Some cases involved the use of more than one AI tool. OpenAI’s ChatGPT (any version, including in-house versions and the ChatGPT-powered app Ghostwriter Legal) was far and away the most common: it was implicated in fully half (18) of the 34 cases that specified a tool. Coming in a distant second were AI tools offered by Westlaw, followed by Anthropic’s Claude (any version), Microsoft Copilot, Google Gemini, and LexisNexis’s AI tools.

This analysis confirms what many lawyers and judges may have suspected: that the archetype of misplaced reliance on AI in drafting court filings is a small or solo law practice using ChatGPT in a plaintiff’s-side representation.

Ultimately, the buck stops with the attorney to make sure that she can stand behind every word of every brief filed over her signature. But the 404 Media article that led me to Charlotin’s database paints a picture of how hard it is to live up to that obligation, particularly for solo or small-firm attorneys. Lawyers struggle with busy caseloads, the trustworthiness of their co-counsel, junior attorneys, and support staff, and personal issues (health problems, caregiving obligations, etc.) that compete with work for their time and attention. Of course, that was already true long before AI. Lawyers, even very good ones, have always made the occasional mistake or oversight in their work. AI tools have merely provided a new way to make those errors – while also promising a way out of the underlying issues that contribute to them, like time crunches and insufficient support. As the 404 Media article observed, “the legal industry is under great pressure to use AI.” To overworked attorneys at small law offices, these tools must seem like a godsend.

However, as the lawyers in this analysis learned the hard way, these tools are not reliable for their core purpose of accurate, comprehensive legal research results. Several of my Stanford colleagues are coauthors on a recent paper that investigated AI legal tools’ claims to be “hallucination-free” or to “eliminate” or “avoid” hallucinations. To the contrary, they found disturbingly high levels of hallucinations in all the tools they studied: OpenAI’s GPT-4, Lexis+ AI (offered by LexisNexis), Westlaw’s AI-Assisted Research, and Ask Practical Law AI (which, like Westlaw, is owned by Thomson Reuters). All of those companies are represented in the 34 cases analyzed above.

The incidents in Charlotin’s database illustrate the real-world impact of AI legal tools’ shortcomings – and not just on the lawyers, who end up humiliated and sanctioned for relying on tools they thought were reliable. AI-tainted legal briefs negatively affect those lawyers’ clients, who depend on them for high-quality representation, including in incredibly high-stakes matters such as criminal prosecutions or the termination of parental rights. They affect opposing counsel, who must waste their time tracking down nonexistent case citations. And they affect the courts, which are busy enough already without also having to police this new form of attorney ethics violations and take care not to let nonexistent cases cited by counsel creep into court opinions.

These cases keep happening at an alarming pace. Dozens of cases have been added to Charlotin’s database since the American Bar Association (ABA) issued its formal opinion warning about generative AI tools in July 2024. For all the news stories about lawyers caught flat-footed by these tools, clearly there are lawyers who never read them and subsequently become the headline of the next one.