ChatGPT Made Up Testimony From Fake Police Officers, State Supreme Court Says

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 (AI) 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 did not return a request for comment by publication time, will investigate and undertake proceedings, the court said.

OpenAI did not respond to a request for comment by publication time.

Aarons told Reuters that he used ChatGPT to summarize the trial proceedings when he agreed to take up the defendant’s appeal last year and did not understand the degree to which AI could “hallucinate” facts.

“I am remorseful but hopeful that the disciplinary board takes into account it was an honest mistake,” he said. “It is a lesson learned for all professionals who rely upon this powerful but sometimes unstable technology.”

Sandoval pleaded not guilty to the murder of the mother of his children before he was convicted and sentenced in 2025 to life in prison.

The appeal is still pending and was assigned on Sept. 2 to Kim Chavez Cook, a New Mexico public defender. Cook declined to comment.

The district attorney’s office for Doña Ana County also declined to comment.

Reuters contributed to this report.