Hallucinated Law vs. the Duty to Verify
Unmasking AI Fabrications in Modern Legal Practice
In the recent CBA Record article, Can Himmel Stem the Tsunami of AI Slop?, the question of whether an attorney’s duty to report opposing counsel's misconduct is triggered for filing documents with AI-generated fabrications.[1] While attorneys are required to report known substantial misconduct by other attorneys, there is no affirmative duty to investigate or police every filing by opposing counsel.
Nevertheless, a recent trend in court rulings suggests that every party must check every citation from every other party. In Noland v. Land of the Free, the court declined to award sanctions against opposing counsel for failing to alert the court to the fabricated citations and becoming aware of them only after the order to show cause.[2] In Elizondo v. City of Laredo, the court urged attorneys to be more diligent in identifying citation errors: "[T]he Court expects all parties to assist in maintaining the integrity of the judicial process by alerting the Court to such errors. The Court encourages greater diligence in flagging citation errors in the future—otherwise, the risk is too great that such errors will persist undetected, potentially leading to an outcome unsupported by law."[3]
In Perez-Castillo v. Blanche, the court discovered many erroneous citations in the petitioner’s brief: “Roughly half of the cases cited in the brief either do not exist or were falsely labeled as Seventh Circuit cases.”[4] The court imposed monetary sanctions of $5,000 on the attorney for failing to check the AI-generated fabricated citations, legal propositions, and factual representations in two briefs he signed and submitted to the court.[5] Notably, during oral argument, the panel asked the government attorney whether they should have noticed the AI errors. The panel indicated that the government’s diligence could have been better and that the brief would have been stronger if it had addressed the fabrications.
In Landberg v. City of New York, the plaintiff allegedly was injured when she tripped and fell on a loose brick in a tree well on a sidewalk.[6] The appellant commenced an action to recover damages for personal injuries against the landowner and the City of New York (the defendants).[7] The trial court granted summary judgment in favor of the defendants; the appellate court affirmed the ruling.[8] Additionally, the appellate court ordered all parties to show cause why sanctions should be (or should not be) imposed against the plaintiff's counsel.[9]
While preparing for this oral argument and reviewing the plaintiff's appellate brief, the court noticed that the brief cited at least three cases that appear to be fictitious.[10] None of these cases or the quoted language seemed to exist.[11] Additionally, there were ten other cases that misrepresented the law. [12] At oral argument, the plaintiff’s counsel was not prepared to comment on the erroneous citations and could not explain how he found the cases.[13] Judge Hector LaSalle also asked counsel for the landowner why these errors were not raised.[14] Judge LaSalle expected opposing counsel to bring the errors to the court’s attention.[15] Judge Valerie Brathwaite Nelson articulated the judiciary’s collective frustration with the endemic problem of AI hallucinations:
The misrepresentations here are of such a degree that they could not merely reflect a difference of opinion . . . . As an appellate court attorney, you would have to, if you were doing the work and reading the briefs and responding to the briefs, you would have to notice that something in the wording of the main brief for the appellant was wrong, if not many things being wrong. It's concerning because we are all officers of the court, and there is a responsibility that you also have to notify the court to do the work, notify the court when these types of misrepresentations and fictitious cases and fictitious citations and misrepresenting the holding of a court of appeals case. I could go on and on, but if you read the brief and looked at the cases, you would have realized it was your responsibility also to alert the court.[16]
Next, the court turned to counsel for the City of New York, asking why counsel failed to bring the fabrications and misrepresentations in the plaintiff's brief to the court's attention.[17] Counsel explained that she had read the brief but focused only on the portion relevant to the City.[18] When the City’s counsel concluded, all of the attorneys attempted to leave the courtroom. However, Judge LaSalle ordered them to stay and take their seats.[19] He then stated:
I just want to say this to you all. This is a very distressing situation. I know this is an outlier. We're very fortunate, my colleagues and I, we have the privilege of working with what I think is one of the best benches in the state, the bars in the state. For me the appellate bar here in the city of New York and its surrounding suburbs, we see excellent work. For me personally, it's been a highlight of my career to have the opportunity to work with such outstanding judges, and to have the opportunity to work with such outstanding lawyers . . . . A part of this profession, a big component of it, is that there's an element of trust, and mistakes are made. We make mistakes as judges, we've made mistakes. I don't want to speak for my colleagues, but I dare say that we've all made mistakes as practitioners, and we work very hard when there are mistakes to try to give the benefit of doubt to those lawyers who practice before us. We know how difficult your respective jobs are. And in reviewing this, I know my colleagues and I have tried to give every benefit of the doubt to the lawyers before us.[20]
Judge LaSalle closed the proceeding by concluding that it was “striking, concerning, disappointing, and saddening to think that members of the bar would forward cases to a court that don’t exist, and to think that the lawyers on the other side of that didn’t read it for whatever reason, didn’t check it.”[21]
Attorneys should always thoroughly review and analyze the legal authorities cited by opposing counsel when preparing a response. This practice is not only essential for effectively countering the other side’s arguments and strengthening one’s own position, but it also serves as a critical safeguard for the integrity of the judicial process. By reading and understanding the cases cited by the opposition, attorneys can identify weaknesses, misrepresentations, or even fabricated authority, which can be leveraged to undermine the opposing argument and potentially secure a favorable outcome. If fabricated authority is discovered, it provides a significant advantage, as courts expect all parties to assist in maintaining the integrity of the process by alerting the court to such errors. Moreover, attorneys have an ethical responsibility to report known substantial misconduct, including the use of fictitious or misrepresented citations, to the appropriate authorities. Ignoring such errors not only risks the persistence of unsupported outcomes but may also expose attorneys to criticism or sanctions for failing to uphold their duties as officers of the court. In sum, diligent review of opposing counsel's citations is both a strategic necessity and a professional obligation.
[1] Frank Young, Can Himmel Stem the Tsunami of AI Slop?, CBA Record, May/June 2026, at 26-28.
[2] Noland v. Land of the Free, 336 Cal. Rptr. 3d 897, 915 (Cal. Ct. App. 2025).
[3] Elizondo v. City of Laredo, No. 25-cv-00050, 2025 WL 2071072, at *3 (S.D. Tex. July 23, 2025).
[4] Perez-Castillo v. Blanche, No. 25-1988, 2026 WL 1533877, at *3 (7th Cir. June 1, 2026).
[5] Id. at *9.
[6] Landberg v. City of New York, No. 2025-02380, 2026 WL 1579730, at *1 (N.Y. App. Div. June 3, 2026).
[7] Id.
[8] Id. at 1-2.
[9] Landberg, 2026 WL 1428993, at *1 (N.Y. App. Div. May 20, 2026).
[10] Samantha Cole, Watch These Judges Rip Into Lawyers For Citing Cases That Don’t Exist, 404 Media (June 4, 2026).
[11] Id.
[12] Id.
[13] Id.
[14] Id.
[15] Id.
[16] Id.
[17] Id.
[18] Id.
[19] Id.
[20] Id.
[21] Id.