After months assailing Robert Mueller as a supposedly biased and unethical prosecutor before the release of his report, Rudy Giuliani shrugged at the news that House Democrats had subpoenaed the special counsel to testify later this month: “Who cares?”

The answer is that a lot of people care what Mueller has to say about President Donald Trump, including many of the former federal prosecutors whose investigations during the 1980s catapulted Giuliani to fame as the hard-hitting U.S. attorney for the Southern District of New York. In interviews with The Daily Beast, Giuliani’s former Justice Department colleagues spoke of Mueller in glowing terms, and most said that his report had set out a triable obstruction of justice case against Trump. Many expressed deep disappointment in Giuliani’s attacks on Mueller and the FBI, albeit with a grudging recognition that his approach has been effective.