What was hallucinated

Fabricated: Case Law | Appellant cited jurisprudences that could not be located and were deemed nonexistent, suspected as AI-generated. || Misrepresented: Case Law | Appellant referenced a real STJ REsp number but misattributed it to a thesis perfectly aligned with the case; court found the cited REsp dealt with a completely different matter.

Details

In this rebuttal, the lawyer cited jurisprudence that the presiding judge (Relator) found to be "impressively so delineated and harmonious with the case". This prompted the judge to investigate the precedent more closely. He discovered that while the case number indicated was real, it belonged to a completely different case unrelated to the legal matter being discussed, leading to the suspicion of an AI "hallucination.The court concluded:"It is totally inconceivable to imagine that the Judiciary, already so burdened with countless lawsuits, needs to investigate all the case law set forth in the legal grounds reported by the parties in the procedural documents, despite the duty to act in good faith set forth in Article 5 of the CPC. After all, it is entirely based on the principle of trust expectation that all subjects act in accordance with existing and valid rules.Thus, even if the appellant claims that such conduct was the result of an error, a claim that has not been satisfactorily proven, but which is taken as a premise for the purposes of argumentation, in the present case, it would be, at the very least, an inexcusable, gross error resulting from serious misconduct, ruling out the possibility of proceeding without any implications in this judicial field, so as not to allow any hesitation in considering the aforementioned conduct as being clearly litigious in bad faith.Thus, as a result of having acted in a manifestly reckless manner (Art. 80, V of the CPC), I condemn the appellant for litigation in bad faith, and he must pay the fine set at 1% of the value of the case (Art. 81 of the CPC), in accordance with the grounds"Translated with DeepL.com (free version)

Sanction teardown · Parana State, Brazil · 2025-06-09

Rodney Chagas v. Fabricio Petinelli Vieira Coutinho

What happened

In Parana State, Brazil, a filing relied on an unnamed/unconfirmed AI tool to help draft legal argument. The court identified the following problems with the citations in that filing:

Fabricated (Case Law)

Appellant cited jurisprudences that could not be located and were deemed nonexistent, suspected as AI-generated.
Misrepresented (Case Law)

Appellant referenced a real STJ REsp number but misattributed it to a thesis perfectly aligned with the case; court found the cited REsp dealt with a completely different matter.

Which AI tool

an unnamed/unconfirmed AI tool. 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 fine (1% of case value)

Additional detail

In this rebuttal, the lawyer cited jurisprudence that the presiding judge (Relator) found to be "impressively so delineated and harmonious with the case". This prompted the judge to investigate the precedent more closely. He discovered that while the case number indicated was real, it belonged to a completely different case unrelated to the legal matter being discussed, leading to the suspicion of an AI "hallucination.The court concluded:"It is totally inconceivable to imagine that the Judiciary, already so burdened with countless lawsuits, needs to investigate all the case law set forth in the legal grounds reported by the parties in the procedural documents, despite the duty to act in good faith set forth in Article 5 of the CPC. After all, it is entirely based on the principle of trust expectation that all subjects act in accordance with existing and valid rules.Thus, even if the appellant claims that such conduct was the result of an error, a claim that has not been satisfactorily proven, but which is taken as a premise for the purposes of argumentation, in the present case, it would be, at the very least, an inexcusable, gross error resulting from serious misconduct, ruling out the possibility of proceeding without any implications in this judicial field, so as not to allow any hesitation in considering the aforementioned conduct as being clearly litigious in bad faith.Thus, as a result of having acted in a manifestly reckless manner (Art. 80, V of the CPC), I condemn the appellant for litigation in bad faith, and he must pay the fine set at 1% of the value of the case (Art. 81 of the CPC), in accordance with the grounds"Translated with DeepL.com (free version)

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.

Check a brief before you file it → · See our live false-verify rate

Source: https://www.damiencharlotin.com/documents/480/Rodney_Chagas_v._Fabricio_Petinelli_Vieira_Coutinho_Brazil_9_June_2025.pdf, via Damien Charlotin's public AI Hallucination Cases Database (CC0).