AI is already enabling people who cannot afford lawyers to find answers to questions such as how to fill out court forms, Justice Roberts said. He said AI can "increase access to justice" with tools that "have the welcome potential to smooth out any mismatch between available resources and urgent needs in our court system."

"But any use of AI," he added, "requires caution and humility" because it risks "dehumanizing the law."

A growing number of lawyers have been using AI in their work, and several lawyers were sanctioned over the summer for including non-existent cases, put forth by AI, as citations in a brief. Some defendants have also said they or their lawyers erroneously used AI in building their cases.

There's also concern about courts using AI in assessing key factors about people who are charged, such as flight risk, due to "potential bias," with studies showing "human adjudications, for all of their flaws, are fairer than whatever the machine spits out," Justice Roberts said.

In the report, addressed to the federal judiciary, he said that "machines cannot fully replace key actors in court," bringing up how judges keep a close eye on the demeanor of defendants when handing down sentences.

"Nuance matters: Much can turn on a shaking hand, a quivering voice, a change of inflection, a bead of sweat, a moment's hesitation, a fleeting break in eye contact," he said.

"And most people still trust humans more than machines to perceive and draw the right inferences from these clues."

AI applications do help advance just, speedy, and inexpensive resolutions to cases, which the federal system is directed to prioritize under federal rules, but as AI evolves, courts must take care in figuring out how AI can be properly used, the chief justice said. The Judicial Conference of the United States, which sets policy for the federal courts, will be involved in that calculus, he said.