What was hallucinated

Fabricated: Case Law | Opposition cites a non-existent Tenth Circuit case styled United States v. Hoffman/Hoffmann. || Misrepresented: Case Law | Opposition lists United States v. Hassan as Tenth Circuit authority; court notes it is a Fourth Circuit case and not binding. || False Quotes: Case Law | Opposition falsely quotes Pure as stating 'reputation and character are inextricably intertwined'; court found the quote does not appear. || Misrepresented: Case Law | Opposition cites Reaves to claim evidence can implicate multiple evidentiary rules; court found Reaves discusses only Rule 608(b) and does not support that proposition. || Fabricated: Case Law | Opposition cites a non-existent Tenth Circuit case styled Perkins v. Fed. Fruit & Produce Co. || Fabricated: Case Law | Opposition cites a non-existent District of Colorado case styled Estate of Martinelli v. City & County of Denver. || Misrepresented: Case Law | Opposition misattributes Ginter as a District of Colorado decision; court notes it is from the Eastern District of Kentucky. || Misrepresented: Case Law | Opposition asserts Perrin supports routine admission of truthfulness evidence in defamation actions; court found Perrin is not a defamation case and does not state that rule.

Details

Prior Order to Show Cause available here.After reviewing - and dismissing - the factual allegations made by Counsel, and noting that they had submitted errata in parallel cases (dealing with other fabricated citations), the court swiftly concluded that they "have violated Rule 11 because they were not reasonable in certifying that the claims, defenses, and other legal contentions contained in Defendants’ Opposition to Motion in Limine [Doc. 283] were warranted by existing law or by a nonfrivolous argument for extending, modifying, or reversing existing law or for establishing new law."Both counsel were sanctioned with a 3,000 USD fine, payable to the court.

Sanction teardown · D. Colorado, USA · 2025-07-07

Coomer v. Lindell/MyPillow, Inc. (1)

What happened

In D. Colorado, USA, a filing relied on Co-Pilot, Westlaw’s AI, Gemini, Grok, Claude, ChatGPT, Perplexity to help draft legal argument. The court identified the following problems with the citations in that filing:

Fabricated (Case Law)

Opposition cites a non-existent Tenth Circuit case styled United States v. Hoffman/Hoffmann.
Misrepresented (Case Law)

Opposition lists United States v. Hassan as Tenth Circuit authority; court notes it is a Fourth Circuit case and not binding.
False Quotes (Case Law)

Opposition falsely quotes Pure as stating 'reputation and character are inextricably intertwined'; court found the quote does not appear.
Misrepresented (Case Law)

Opposition cites Reaves to claim evidence can implicate multiple evidentiary rules; court found Reaves discusses only Rule 608(b) and does not support that proposition.
Fabricated (Case Law)

Opposition cites a non-existent Tenth Circuit case styled Perkins v. Fed. Fruit & Produce Co.
Fabricated (Case Law)

Opposition cites a non-existent District of Colorado case styled Estate of Martinelli v. City & County of Denver.
Misrepresented (Case Law)

Opposition misattributes Ginter as a District of Colorado decision; court notes it is from the Eastern District of Kentucky.
Misrepresented (Case Law)

Opposition asserts Perrin supports routine admission of truthfulness evidence in defamation actions; court found Perrin is not a defamation case and does not state that rule.

Which AI tool

Co-Pilot, Westlaw’s AI, Gemini, Grok, Claude, ChatGPT, Perplexity. Note: Charlotin's public database records tool attribution only where a court order, brief, or reporting on the matter states it explicitly; "unidentified" or "implied" means the record indicates AI use but does not name a specific product — we do not guess.

Outcome

Monetary Sanctions (monetary penalty: 6000 USD.)

Additional detail

Prior Order to Show Cause available here.After reviewing - and dismissing - the factual allegations made by Counsel, and noting that they had submitted errata in parallel cases (dealing with other fabricated citations), the court swiftly concluded that they "have violated Rule 11 because they were not reasonable in certifying that the claims, defenses, and other legal contentions contained in Defendants’ Opposition to Motion in Limine [Doc. 283] were warranted by existing law or by a nonfrivolous argument for extending, modifying, or reversing existing law or for establishing new law."Both counsel were sanctioned with a 3,000 USD fine, payable to the court.

How Citation Safe would have caught this

Citation Safe runs three deterministic layers before a brief is filed: (1) does the citation exist against CourtListener's database of published opinions, (2) if quoted, does that exact language appear in the source, (3) does the cited case actually support the proposition it is cited for. Fabricated case citations fail Layer 1. Fabricated or misattributed quotations fail Layer 2 even when the underlying case is real. Misrepresented holdings — a real case cited for a proposition it does not support — are the target of Layer 3. None of these checks involve asking another language model whether the citation looks right; they are lookups and text-matches against the actual source, which is why a hallucinated citation has to survive a direct lookup against the authoritative source — not another model's opinion — to earn a VERIFIED stamp; our measured false-verify rate is published live at /quality.

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Source: https://www.damiencharlotin.com/documents/566/Coomer_v._Lindell_USA_7_July_2025.pdf, via Damien Charlotin's public AI Hallucination Cases Database (CC0).