Landberg v. City of New York: an AI-fabricated appellate brief drew $10,500 in sanctions

The problem

An attorney’s court filing is only as trustworthy as its citations. Generative-AI research tools will fabricate case names, invent quotations, and misstate holdings with complete fluency, and an appellate brief that repeats them without verification wastes the opposing party’s time, burdens the court, and can deprive the client of arguments grounded in real precedent.

What was built

In Landberg v City of New York (Appellate Division, Second Department, Docket 2025-02380, Index No. 509670/18), the plaintiff’s appellant’s brief, submitted by attorney Michael Sanders of the Law Offices of Michael S. Lamonsoff, PLLC, was, in the court’s own words, a “brief, prepared with the assistance of generative artificial intelligence (hereinafter GenAI), containing citations to nonexistent cases, fictitious purported Court of Appeals quotations wholly contrary to actual law, and misrepresentations about what certain real cases actually held or decided” (source). The underlying case was a sidewalk trip-and-fall over a loose brick in a tree well; the AI-drafted brief was the vehicle for the sanctioned conduct, not the merits (source).

The court found the brief “cited to several nonexistent cases, misstated the law, and misrepresented the holdings of real cases” (source). It relied on three fictitious cases, Xiang Fu Ji v City of New York (13 NY3d 791, 794), Hausser v Giunta (88 AD3d 969, 970), and Lack v Lack (841 NYS2d 403, 404), and twice quoted a fabricated Court of Appeals passage saying Administrative Code section 7-210 should be “construed liberally to effectuate its remedial purpose” when the Court of Appeals has actually held that provision “must be strictly construed” (source). Sanders acknowledged submitting a brief “to this Court unknowingly with three fabricated citations,” which he believed “originated during the AI-assisted portion of [his] supplemental research which [he] negligently failed to verify” (source). He stated he did “not recall which exact tool [he] used, it was one of the free ones available to the public” (source).

The outcome

The sanction on the attorney: $8,000. Acting under 22 NYCRR 130-1.1, the court held “we deem it appropriate to impose a monetary sanction on Sanders in the sum of $8,000” and directed him to pay it to the Lawyers’ Fund for Client Protection of the State of New York (source).

The sanction on the firm: $2,500. Because “the law firm’s name appeared on a brief that contained significant misrepresentations, and in light of the deterrent purpose of sanctions,” the court imposed a further $2,500 on the Law Offices of Michael S. Lamonsoff, PLLC, to the same fund, for a combined $10,500 (source). The NY Daily Record reported the same total: “monetary sanctions totaling $10,500 for an attorney and his law firm” (source).

The candor finding. The court weighed “Sanders’s lack of candor”: at oral argument he first said the authorities came from Lexis, Westlaw, a book, or a prior case, and only later admitted in an affirmation that he “should have stated that they were hallucinated by artificial intelligence,” explaining he “was genuinely scared at the time” (source).

The open question. The court noted the matter before it “is limited to whether the conduct of the attorney and the law firm warrants sanctions. Whether disciplinary action is also warranted may be a matter for the Attorney Grievance Committee” (source).

Conflation guards. The opinion names no AI product, so it is not attributable to any brand; the $250 figure in the opinion is a different case (Matter of Julien v Arthur) cited by comparison, not part of this sanction; and the sidewalk-injury merits are unrelated to the AI conduct (source).

How this was verified

This is a court-origin record, not a vendor claim, and it carries a green badge under TIN’s public-record standard. On 2026-08-16 the published appellate opinion (2026 NY Slip Op 03935) was re-fetched live from the official New York State Law Reporting Bureau site, and every figure and quotation above was checked against it verbatim. The $8,000/$2,500/$10,500 figures and the Grievance Committee note are independently corroborated by the NY Daily Record (Bennett Loudon, 2026-06-26). The earlier 404 Media report (Samantha Cole, 2026-06-04) corroborates the fabricated citations and the oral argument but predates the sanction decision and does not state the dollar figures; it is used only for what it actually covers. No confirmation was sought from Sanders, his firm, or any vendor: green never depends on the subject confirming anything.

Related case files

The same New York sanctions regime under 22 NYCRR 130-1.1 produced New York’s first appellate AI-sanction in Deutsche Bank Natl. Trust Co. v LeTennier, which the Landberg court cites as controlling precedent on how appellate sanctions should deter the bar at large. For a state appellate court reaching the same $10,000-scale penalty on the other side of the country, see Noland v. Land of the Free, California’s first published opinion on AI-fabricated citations. And for the same failure inside a large firm rather than a solo appeal, Wadsworth v. Walmart shows a federal judge fining Morgan and Morgan lawyers $5,000 after AI hallucinated eight of nine cited cases.

Sources

Tier 1 = the published court opinion (primary). Tier 2 = independent press naming the parties. Each source was checked against the live page or its archived capture on 2026-08-16.

1. New York State Law Reporting Bureau, “Landberg v City of New York, 2026 NY Slip Op 03935,” decided 2026-06-23 (Tier 1, primary court opinion; re-fetched live 2026-08-16). https://www.nycourts.gov/reporter/current/3dseries/2026/2026_03935.shtml
2. NY Daily Record, “New York attorney, law firm sanctioned for AI fake citations” (Bennett Loudon), 2026-06-26 (Tier 2, independent newsroom; corroborates the $8,000/$2,500/$10,500 figures and the Grievance Committee note; via Wayback full-body capture, digest GWIC6HTCDL773BGJYFKCOTOZLESJ5VJE). https://web.archive.org/web/20260627090232/https://nydailyrecord.com/2026/06/26/new-york-attorney-law-firm-sanctioned-ai-fake-citations/
3. 404 Media, “Watch These Judges Rip Into Lawyers For Citing Cases That Don’t Exist” (Samantha Cole), 2026-06-04 (Tier 2, independent newsroom; covers the oral argument and fabricated citations, predates the sanction decision and does not state the dollar figures). https://www.404media.co/new-york-court-ai-citations-landberg-case/