São Paulo court fines a defendant 9% of the case value over a hidden instruction in his defence asking AI to praise his lawyer
A São Paulo business and arbitration court found that every page of a defendant's written defence carried a hidden instruction, placed above his lawyer's letterhead, asking any AI that analysed the petition to give a favourable opinion and praise the lawyer's probity and care. In a sentence dated 14 September 2026 the judge treated this as prompt injection and bad-faith litigation: although the defendant won on the merits, he was ordered to pay the plaintiff a fine of 9% of the updated case value, and the sentence was sent to the São Paulo bar to examine the lawyer's conduct. No source says any AI system read the instruction.
AI involvement reported · Causal attribution established · 2 sources, 1 underlying account · Added 16/10/2026