A legal brief that argued for overturning a murder conviction contained fake testimony from fabricated witnesses, including supposed police officers who do not exist, according to New Mexico’s Supreme Court.

Stephen D. Aarons, a lawyer representing convicted murderer Oscar Renee Sandoval, admitted to using ChatGPT, an artificial intelligence tool made by OpenAI, when developing his primary brief in the case, the court said in a four-page order on Sept. 9.

“Respondent admitted to the Court that the brief in chief contained false testimony from wholly fabricated witnesses—Officer Michelle Amarillo, Officer Sanchez, Manal Al-Jibury, and Teresa Marquez; false testimony from Danny Stanton that he received threats, which he took seriously, from Defendant-Appellant; false testimony from Linda Stanton about the threats her husband received; false testimony from Mariah Chavez and Teresa Marquez (fabricated witness) regarding the shooter’s clothing and appearance; and misrepresented legal authority” in citing multiple cases, the court said.

Aarons signed the brief despite not verifying the factual claims and legal authority in the AI-generated document, the court said. He did not inform his client of the failure to verify or that the brief contained incorrect information.

Aarons also acknowledged not informing his client after the court discovered the misrepresentations.

That constituted a lack of remorse and a lack of concern for the client, the state’s top court said.

It found Aarons, who is based in Santa Fe, in contempt of court, barred him from appearing before the court, fined him $5,000, and referred him to the Disciplinary Board of the New Mexico Supreme Court. The board, which declined to comment, will investigate and undertake proceedings, the court said.

OpenAI did not respond to a request for comment.

Aarons told The Epoch Times in an email that after he agreed to handle the appeal, he used ChatGPT to summarize trial proceedings.

“I wrote the brief, but the table of contents and the summary contained numerous errors,” he said. “At the time, I didn’t know that AI could hallucinate facts not only in my brief, but in pleadings submitted by other attorneys.

“I am glad the court threw out my defective pleading and ordered the public defender to write a new brief on behalf of my former client. As for myself, I am remorseful but hopeful that the disciplinary board takes into account it was an honest mistake. It is a lesson learned for all professionals who rely upon this powerful but sometimes unstable technology.”