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Incident Tracker / United States (federal)

McCarthy v. U.S. Drug Enforcement Administration (3d Cir. 2026), No. 24-2704

·US Court of Appeals for the Third Circuit·US-FEDWarning

The US Court of Appeals for the Third Circuit reprimanded an attorney whose opening brief contained AI-hallucinated case summaries and a nonexistent authority that he failed to correct. As its first AI-hallucination case, the court withheld monetary sanctions but warned that future violators may face them.

Court
US Court of Appeals for the Third Circuit
Date
2026-03-27
Who used the AI
Not recorded
AI tool
AI (unspecified)
Conduct
Petitioner's counsel filed an opening brief with incorrect, hallucinated case summaries and one nonexistent authority generated by AI, and failed to correct them after the government flagged the errors. The court reprimanded counsel under its Disciplinary Rules and directed notification of all courts of his admission and the National Disciplinary Data Bank.
Outcome
Warning
Penalty
No monetary penalty recorded
Regulatory outcome
No separate regulatory disposition recorded
Status
Verified against listed sources
Last checked
2026-09-16

What was fabricated or misused

  • Eight DEA adjudication summaries in the opening brief — seven inaccurate and one nonexistent; the Third Circuit did not list the adjudication names
  • Reply brief characterisation of the errors as “immaterial misstatements” and “minor discrepancies” — made without checking the authorities

What the court said

“Attorney “modified some of the [provided] language for ease of reading and then simply incorporated the same into the brief” without verifying the existence or accuracy of the citations.”
US Court of Appeals for the Third Circuit, slip op. at 3
“It was at this point that Attorney finally checked the authorities, and discovered for himself the summaries’ inaccuracies and the fact that one cited adjudication did not exist.”
US Court of Appeals for the Third Circuit, slip op. at 4
“We conclude that Attorney’s conduct violated R.P.C. 1.1 in that he failed to exercise the “thoroughness [] necessary for the representation” in this matter.”
US Court of Appeals for the Third Circuit, slip op. at 8
“Had this not been our first opportunity to address the use of AI, and had we given notice that we would consider whether Attorney’s conduct violated Pa. R.P.C. 1.1, it is likely that monetary sanctions would have been imposed here.”
US Court of Appeals for the Third Circuit, slip op. at 13

Timeline

  1. Counsel filed the opening brief with eight DEA adjudication summaries.
  2. Counsel filed a reply brief calling the errors immaterial.
  3. The court ordered counsel to provide copies of the eight adjudications.
  4. The court issued an order to show cause on discipline.
  5. The Third Circuit held the disciplinary hearing.
  6. The court issued a public reprimand and warned of future monetary sanctions.

Why this case matters

McCarthy is the Third Circuit's first precedential discipline opinion on AI-generated legal research. Compared with Mata v Avianca, it involved administrative adjudication summaries rather than ordinary case citations, and the false material was supplied through a non-attorney. Compared with Prososki v Regan, the court imposed only a reprimand because it had not yet addressed AI guardrails and had not noticed Rule 1.1 in the show-cause order. The opinion removes those mitigating factors for later Third Circuit lawyers.

Practice note

When a non-attorney or AI tool supplies authority summaries, the signing lawyer must check both existence and accuracy before filing. The check needs the underlying adjudication or opinion, not a summary. If the government or another party flags errors, counsel must read the authorities immediately, correct the record, and disclose any AI-generated source rather than file a reply that minimizes unverified mistakes.

Primary sources for this incident

Related regulation records for this incident

No related regulation record has been linked to this incident yet.

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Cite this record

SafeLegalAI Global Legal AI Incident Tracker, “McCarthy v. U.S. Drug Enforcement Administration (3d Cir. 2026), No. 24-2704”, safelegalai.com/tracker/mccarthy-v-dea (accessed 2026-09-16). Data: CC BY 4.0.

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