A ChatGPT Brief Invented Four Witnesses. A Court Fined the Lawyer $5,000.

Stephen Aarons, a New Mexico defense lawyer of more than 40 years, was held in contempt and referred to a disciplinary board.

A New Mexico defense lawyer was fined $5,000 for filing an appeal brief that quoted witnesses who never testified. The New Mexico Supreme Court entered the order on Wednesday, September 9, 2026. It held the attorney, Stephen Aarons, in direct contempt and referred him to a disciplinary board, Ars Technica reported.

The person carrying the cost of it is in prison. Aarons's now-former client, Oscar Renee Sandoval, was sentenced to life in February 2025. He was convicted of killing Shiereen Al-Jibury, his partner and the mother of his children.

The court has now struck every brief filed in Sandoval's appeal, ordered the public defender's office to assign him a new lawyer, and pushed the case into its 2026-27 term. Chief Justice Julie Vargas told Aarons at a hearing that Sandoval stays in custody until the matter is sorted out.

Aarons admitted he didn't verify the factual claims or the legal authority in the AI-generated brief before signing and filing it, the order says. He didn't tell his client about any of it either. The order says the brief contained “false testimony from wholly fabricated witnesses.” It names four: Officer Michelle Amarillo, Officer Sanchez, Manal Al-Jibury and Teresa Marquez. Invented quotes were also attributed to real people, about threats and about the shooter's clothing.

He didn't cite cases that don't exist, which is the familiar version of this failure. He described real ones inaccurately instead, the order says.

At an August 21, 2026 hearing, Aarons told the justices he'd run a computer-generated trial transcript and other case materials through ChatGPT. He used a version powered by OpenAI's o3 model, he said. The chatbot produced the quotes. He'd assumed the output was a reliable summary of the proceedings because AI use is so widespread in law and medicine, he told the court. The audio had first been transcribed by Rev.com, he said, and the trouble started after he loaded that transcript into the chatbot.

Justice C. Shannon Bacon wasn't having the explanation. Her 13-year-old nephew and her 75-year-old stepmother both know AI tools make things up, she said. She told Aarons he'd violated eight or nine provisions of the code of conduct. He'd either kept himself deliberately uninformed or taken a gamble, she said, and staying uninformed is a choice somebody makes.

Justice Michael Vigil said the tool is beside the point. A lawyer who files work without checking it is responsible either way, he said, whether the draft came from a chatbot or from a junior attorney. Bacon made a related point about the citations. There's no meaningful difference between misdescribing a real case and inventing one, she said, because the duty of candor applies the same.

The fine goes to the State Bar of New Mexico Client Protection Fund. Aarons is also barred from appearing before the state Supreme Court while the disciplinary investigation runs. The court said more penalties could follow. That board hasn't ruled.

Bacon pressed Aarons on whether Sandoval knew. He said he hadn't told him. He'd told Sandoval's brother and cousin, who hired him, only that there was a problem with the first brief. In a statement to Ars Technica, Aarons said he hadn't known AI could hallucinate facts. He added: “I am remorseful but hopeful that the disciplinary board takes into account it was an honest mistake.”

The appeal starts over, with a public defender writing the brief.

Source: arstechnica.com, retrieved September 14, 2026.