By John Kruzel WASHINGTON (Reuters) -Artificial intelligence represents a mixed blessing for the legal field, U.S. Supreme Court Chief Justice John Roberts said in a year-end report published on Sunday, urging “caution and humility” as the evolving technology transforms how judges and lawyers go about their work. Roberts struck an ambivalent tone in his 13-page report. He said AI had potential to increase access to justice for indigent litigants, revolutionize legal research and assist courts in resolving cases more quickly and cheaply while also pointing to privacy concerns and the current te…