AI Hallucination Cases

"This case adds yet another unfortunate chapter to the story of artificial intelligence misuse in the legal profession. Here, Defendants' counsel not only included an AI-hallucinated citation and quotations in the summary judgment brief that led to the filing of this motion for sanctions, but also included multiple new AIhallucinated citations and quotations in Defendants' brief opposing this motion. In other words, counsel relied upon unvetted AI—in his telling, via inadequately supervised colleagues—to defend his use of unvetted AI."

"Were Advani a lawyer, the Court would consider imposing sanctions on her. But in view of the fact that she is not a lawyer and of the dismissal of this case, the Court declines to pursue the matter further and merely warns Advani that presentation of false citations, quotations, and holdings in the future may indeed result in the imposition of sanctions."

The district court independently found numerous inaccurate quotations and citations in Plaintiff's Opposition—misquoted language attributed to binding Third Circuit authority, Westlaw citations and dates that were incorrect or non-existent, and miscited pincites. The court concluded the pattern suggested the brief may have been prepared using generative AI without adequate verification and ordered counsel to show cause under Rule 11 and ethical rules. The court preserved the inaccuracies in the official opinion but removed links to invalid citations.

AI Use

Alim Al-Hamim, appearing pro se (self-represented), used a generative AI tool to prepare his opening brief appealing the dismissal of his claims against his landlords. He had also submitted a document with fabricated citations in the lower court.

Hallucination Details

The appellate brief contained eight fictitious case citations alongside legitimate ones. The court could not locate the cases and issued an order to show cause.

Ruling/Sanction

Al-Hamim admitted relying on AI, confirmed the citations were hallucinations, stated he failed to inspect the brief, apologized, and accepted responsibility. The court affirmed the dismissal of his claims on the merits. While finding his submission violated Colorado Appellate Rules (C.A.R. 28(a)(7)(B)), the court exercised its discretion and declined to impose sanctions.

Key Judicial Reasoning

Factors against sanctions included Al-Hamim's pro se status, his contrition, lack of prior appellate violations, the absence of published Colorado precedent on sanctions for this issue, and the fact that opposing counsel did not raise the issue or request sanctions. However, the court issued a clear and strong warning to "the bar, and self-represented litigants" that future filings containing AI-generated hallucinations "may result in sanctions". The court emphasized the need for diligence, regardless of representation status.

In an earlier decision, the court had already warned the plaintiff against "any further legal misrepresentations in future communications".

Defendant Holly Nelson, appearing pro se, filed a motion to dismiss that included a fabricated case citation, Finch v. Smith, which does not exist. The court inferred that Nelson used AI to draft the motion without verifying the accuracy of the citations. The court issued an order to show cause, requiring Nelson to justify why her filing does not violate Rule 11, or alternatively, to withdraw her motion. If she fails to do so, the court intends to strike her motion entirely.

The underlying motion was later withdrawn, with the result that the tentative ruling was not adopted.

AI Use

The plaintiff, proceeding pro se, submitted filings citing multiple nonexistent cases. The court noted patterns typical of ChatGPT hallucinations, referencing studies and prior cases involving AI errors, though the plaintiff did not admit using AI.

Hallucination Details

Several fake citations identified, including invented federal cases and misquoted Supreme Court opinions. Defendants flagged these to the court, and the court independently confirmed they were fictitious.

Ruling/Sanction

No sanctions imposed at this stage, citing special solicitude for pro se litigants. However, the court issued a formal warning: further false citations would lead to sanctions without additional leniency.

Key Judicial Reasoning

The court emphasized that even pro se parties must comply with procedural and substantive law, including truthfulness in court filings. Cited Mata v. Avianca and Park v. Kim as established examples where AI-generated hallucinations resulted in sanctions for attorneys, underscoring the seriousness of the misconduct.

"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."

The Board found over 70% of citations in Huffman's reply brief inaccurate, including fabricated cases, misattributed reporter citations, cases that did not support cited propositions, and incorrect or non-existent transcript/Rule 4 citations. Counsel admitted using AI to generate portions of the brief. The Board treated the motion as one for Rule 11-type sanctions and struck the reply brief; it emphasized attorneys' duty to verify AI-generated content.

AI Use

Counsel admitted using a “new legal research medium”, appears to be a generative AI system or platform capable of generating fictitious case law. Counsel did not deny using AI, but claimed the system may have been corrupted or unreliable. The amended filing removed the false authorities.

Hallucination Details

The court did not identify the specific fake cases but confirmed that “citations to non-existent cases” were included in Defendants’ original brief. Counsel’s subsequent filing corrected the record but did not explain how the citations passed into the brief in the first place.

Ruling/Sanction

Judge William Griesbach denied the motion for summary judgment on the merits, but addressed the citation misconduct separately. He cited Rule 11 and Park v. Kim (91 F.4th 610, 615 (2d Cir. 2024)) to underline the duty to verify. No formal sanctions were imposed, but counsel was explicitly warned that further use of non-existent authorities would not be tolerated.

Key Judicial Reasoning

The court emphasized that even if the submission of false citations was not malicious, it was still a serious breach of Rule 11 obligations. Legal contentions must be “warranted by existing law,” and attorneys are expected to read and confirm cited cases. The failure to do so, even if caused by AI use, is unacceptable. The court accepted counsel’s corrective effort but insisted that future violations would be sanctionable.

The court found multiple exhibits (videos, photographs, messaging screenshots, and metadata) to be fabricated or materially altered using generative AI. The court deemed Plaintiffs' explanations not credible, declined criminal referral, declined monetary sanctions, and imposed a terminating sanction under Cal. Civ. Proc. Code § 128.7(b).

" While in our discretion we will not impose sanctions on petitioner, who is proceeding pro se, we warn petitioner that continuing to cite nonexistent caselaw could result in the imposition of sanctions in the future. "

AI Use

The plaintiff, proceeding pro se, cited “Darling v. Linde, Inc., No. 21-cv-01258, 2023 WL 2320117 (D. Or. Feb. 28, 2023)” in briefing. The court stated it could not locate the case in any major legal database or via internet search and noted this could trigger Rule 11 sanctions if not based on a reasonable inquiry. The ruling cited Saxena v. Martinez-Hernandez as a cautionary example involving AI hallucinations, suggesting the court suspected similar conduct here.

AI Use

Counsel used ChatOn to rewrite a reply brief with case law, under time pressure, without verifying the outputs. The five cases did not exist; citations were entirely fictional. Counsel later admitted this in a sworn declaration and at hearing, describing her actions as a lapse caused by workload and inexperience with AI.

Hallucination Details

Fabricated cases included:

• Klein v. E.I. Du Pont de Nemours & Co., 406 F.2d 1004 (cited case does not exist)
• Gordon v. N.Y. Cent. R.R. Co., 202 F. Supp. 2d 290
• Mitchell v. JCG Industries, 2010 WL 11627832
• Hollander v. Sweeney, 2005 WL 19904045
• Davis v. S. Farm Bureau Cas. Ins. Co., 2019 WL 3452601

None of these cases matched any legal source. Counsel filed them as part of a sworn statement under penalty of perjury.

Ruling/Sanction

The court imposed a $1,000 sanction payable to the Clerk; ordered the counsel to serve the order on her client and file proof of service. The court acknowledged her sincere remorse and remedial CLE activity, but emphasized the seriousness of submitting hallucinated cases under oath. Sanctions were tailored for deterrence, not punishment.

Key Judicial Reasoning

Quoting Park v. Kim and Mata v. Avianca, the court held that submitting legal claims based on nonexistent authorities without checking them constitutes subjective bad faith. Signing a sworn filing without knowledge of its truth is independently sanctionable. Time pressure is not a defense. Lawyers cannot outsource core duties to generative AI and disclaim responsibility for the results.

In the November 2024 Show Cause Order, Judge Robinson noted that: "First, the briefing does not cite the forum-selection clause from the contract between the parties; instead, it cites and quotes a forum-selection clause that appears nowhere in the papers submitted by the parties. Second, Defendant’s reply brief includes a citation, Hogan v. Allstate Insurance Co., No. 19-CV-00262-JPM, 2020 WL 1882334 (D. Kan. Apr. 15, 2020), in which the court purportedly “transferred a case to the Southern District of Texas because the majority of the witnesses were located in Texas. The court found that the burden on the witnesses outweighed the convenience of litigating the case in Kansas.” As far as the Court can tell, this case does not exist. The Westlaw database number pulls up no case; the Court has found no case in CM/ECF between the parties “Hogan” and “Allstate Insurance Co.” Moreover, docket numbers in this district have at least four digits—not three—after the case-type designation, and there is no judge in this district with the initials “JPM.”"

During the show cause hearing (Transcript), Counsel apologised and pledged to reimburse the other side's costs, as well as his client's.

AI Use

Counsel filed opposition briefs citing two nonexistent cases. The court suspected generative AI use based on "hallucination" patterns but Counsel neither admitted nor explained the citations satisfactorily. Failure to comply with a standing AI order aggravated sanctions.

Hallucination Details

Two fake cases cited. Citation numbers and Westlaw references pointed to irrelevant or unrelated cases. No affidavit or real case documents were produced when ordered.

Ruling/Sanction

Counsel's appearance was struck with prejudice. The Court ordered notification to the State Bar of Pennsylvania and the Eastern District Bar. Consel was required to inform his client, Bevins, of the sanctions and the need for new counsel if re-filing.

The court held that: "It is likely that Appellant employed argument generated by an artificial intelligence (AI) program which contained the fictitious case citation and cautions Appellant that many harms flow from the use of non-existent case citations and fake legal authority generated by AI programs, including but not limited to the waste of judicial resources and time and waste of resources and time of the opposing party. Were courts to unknowingly rely upon fictitious citations, citizens and future litigants might question the validity of court decisions and the reputation of judges. If, alternatively, Appellant's use of a fictitious case was not the result of using an AI program, but was instead a conscious act of the Appellant, Appellant's action could be deemed a fraud on the Court. Appellant is hereby expressly warned that submission of fictitious case authorities may subject Appellant to sanctions under the S.C. Frivolous Proceedings Act, S.C. Code Ann. § 15-36-10(Supp. 2024)."

In her latter response to the Court, Counsel apologised for her use of a "a non-firm approved general AI service".

Although no immediate sanctions were imposed, Magistrate Judge Ho explicitly warned Plaintiff that future misconduct of this nature may violate Rule 11 and lead to consequences.

In a subsequent Order, the court pointed out that "This Court's opinion pointing out Buckner's citation to nonexistent case law, along with its implications, is an issue for appeal and not a valid basis for recusal. "

AI Use

Counsel admitted using ChatGPT to draft two motions (Motion to Withdraw and Motion for Leave to Appeal), without verifying the cases or researching the AI tool’s reliability.

Hallucination Details

2 Fake cases:

• McNally v. Eyeglass World, LLC, 897 F. Supp. 2d 1067 (D. Nev. 2012) — nonexistent
• Behm v. Lockheed Martin Corp., 460 F.3d 860 (7th Cir. 2006) — nonexistent

Misused cases:

• Degen v. United States, cited for irrelevant proposition
• Dow Chemical Canada Inc. v. HRD Corp., cited despite later vacatur
• Eavenson, Auchmuty Greenwald v. Holtzman, cited despite being overruled by Third Circuit precedent

Ruling/Sanction

The Court sanctioned Counsel $2,500 payable to the court and ordered him to complete at least one hour of CLE on AI and legal ethics. The opinion emphasized that deterrence applied both specifically to Counsel and generally to the profession.

Key Judicial Reasoning

Rule 11(b)(2) mandates reasonable inquiry into all legal contentions. No AI tool displaces the attorney’s personal duty. Novelty of AI tools is not a defense.

In May, the court asked Counsel to show cause why they should not be sanctioned for filing briefs with hallucinations - especially since they continued filing hallucinated submissions after being warned about it.

In their Answer, Counsel revealed that "specific citations and quotes in question were inadvertently derived from internal draft text prepared using generative AI research tools designed to expedite legal research and brief drafting".

In the Order, the court noted that Counsel "was not candid to the Court when confronted about his use of AI, stating that some of these documents were “prepared under time constraints,” when he had nearly two more weeks before the deadline to submit his responses." The judge was also unimpressed by Counsel's attempt to shift the blame to a paralegal.

Finally, in the fee dispute order, the court cited this database to point out that its approach to award costs and fees was appropriate, especially given the egregiousness of the claimant's conduct in this case. The judge also took into account "the significant, if indirect, monetary losses that may arise from nonmonetary sanctions in other cases, such as loss of business and loss of reputation, or the monetary loss borne by a client when a motion or even an entire case is adversely decided due to counsel’s misuse of AI."

The appellate court dismissed the appeals due to lack of jurisdiction and ordered respondent's appellate Counsel to pay $1,000 in monetary sanctions for violating Illinois Supreme Court Rule 375 by citing multiple cases that did not stand for the propositions of law for which they were cited. The court also ordered a copy of the decision to be sent to the Illinois Attorney Registration and Disciplinary Commission.

Counsel had previously admitted to using AI to prepare briefs in another case (in Re Boy) without thoroughly reviewing the work-product, leading to similar issues. The court found it reasonable to conclude AI was used in this case as well, although not explicitly admitted by Counsel.

AI Use

The court did not specify how the hallucinated material was generated but described the bulk of appellant’s cited cases as “phantom case law.”

Hallucination Details

The court identified that the “Augmented Appendix Sections” attached to each brief consisted of numerous nonexistent Florida cases. Some real cases were cited, but quotes attributed to them were fabricated.

Ruling/Sanction

Dismissal of both consolidated appeals as a sanction. Bar on further pro se filings in the underlying probate actions without review and signature of a Florida-barred attorney. Clerk directed to reject noncompliant future filings

Key Judicial Reasoning

The Court held that Gutierrez’s submission of fictitious legal authorities and failure to respond to the show cause order constituted an abuse of process. It emphasized that pro se litigants are bound by the same rules as attorneys and referenced prior sanctions cases involving AI hallucinations.

"Counsel should take seriously its obligation to provide the Court with an accurate description of the law. See, e.g., United States v. Hayes, 763 F. Supp. 3d 1054 (E.D. Cal. 2025) (levying $1,500 in monetary sanctions against counsel personally for fictitious cases and quotations that the court suspected were produced using artificial intelligence),reconsideration denied, No. 2:24-CR-0280-DJC, 2025 WL 1067323 (E.D. Cal. Apr. 9, 2025); Grant v. City of Long Beach, 96 F.4th 1255 (9th Cir. 2024) (striking an appellant's brief and dismissing an appeal for materially misrepresenting or fabricating case citations). After New Materials freely accused opposing counsel of misstating the law, New Materials’ submission of non-existent quotes is troubling (Dkt. 30 at 5 (“Chenco's argument for remand collapses under the weight of its own misreading of the law”); id.at 7 (“Chenco fundamentally misrepresents the applicable removal standard”); Dkt. 34 at 1 (“The proposed sur-reply ... is necessary to address new legal misstatements ....”); id. at 2-3 (“Chenco's failure to address this standard ... misstates controlling law and warrants correction.”)). Accordingly, the Court reminds counsel of their duties to act according to the Idaho Rules of Professional Conduct."