The Digital Hallucination: A CZK 25,000 Lesson in AI Legal Ethics

The rapid integration of Artificial Intelligence brings new risks to the legal profession. The Czech judiciary is now beginning to penalize respective violations of attorney duty of care. A landmark decision by the Constitutional Court (file no. I. ÚS 3004/25) serves as a vital warning for legal professionals who rely on AI-generated content without rigorous verification. In this case, the Court imposed a disciplinary fine of CZK 25,000 on an attorney whose submission was found to be based on "hallucinated" legal authorities.

A lawyer filed a constitutional complaint that appeared, at first glance, to be a standard, professional document. However, upon a detailed review by the Court, it was discovered that a significant portion of the cited jurisprudence was entirely fabricated. Out of the 12 decisions of the Czech Constitutional Court and the European Court of Human Rights referenced in the complaint, several simply did not exist. For instance, the attorney cited specific "judgments" regarding the unconstitutionality of certain procedural codes that the Court had never actually issued. Other citations pointed to real file numbers but were "grossly misinterpreted," describing legal principles that were nowhere to be found in the actual rulings.

The Court’s reasoning highlights a critical technological shift. The Court noted that the submission displayed classic symptoms of Large Language Model (LLM) usage: unnatural "Anglicisms," inconsistent citation formats, and a fundamental failure to distinguish between different types of court rulings, such as a "judgment" (nález) versus a "resolution" (usnesení). This led the Court to conclude that the attorney had used AI to generate the arguments but failed to perform the essential professional task of verifying the output.

This decision reinforces a fundamental principle of the legal profession: responsibility is non-delegable. Whether an attorney uses a junior lawyer or a generative AI model to draft a brief, the attorney remains fully liable for the accuracy of the filing. The Court emphasized that the purpose of mandatory legal representation is to ensure communication at a high formal and substantive level, protecting the client from procedural harm. By submitting "hallucinated" arguments, the attorney was found to have grossly obstructed the proceedings by misleading the Court and causing unnecessary delays.

While the maximum fine for such conduct is CZK 100,000, the Court opted for a penalty at the lower end of the spectrum because it was the attorney's first offense and the defects in the complaint could still be remedied. For legal practitioners this case is a clear signal: while AI can be a powerful assistant, it lacks the professional judgment and factual accuracy required in a courtroom. Every citation generated by a machine must be treated as suspect until manually confirmed against an official legal database.

By JUDr. Ondřej Rathouský

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