One of the key special counsel prosecutors to explore whether President Trump obstructed justice is headed to private practice, and he said in an interview he will try to bring with him the ethos that Robert S. Mueller III instilled in his investigators.

Andrew Goldstein, a senior assistant special counsel under Mueller, will join the Cooley law firm as a litigation partner working in New York and Washington, the firm announced Monday. In an interview, Goldstein declined to address the specifics of his special counsel work but talked broadly about what it was like to work under Mueller in the special counsel’s office — which he called “the privilege of a lifetime.”

“He is an extraordinary public servant, and he created an environment in our office where our only mission was to do the right thing for the right reasons,” Goldstein said. “And in private practice, I very much believe in the law and being a lawyer in a way that helps serve the public good, and I’m hoping to find ways to continue to do that at Cooley.”

As part of the special counsel team, Goldstein played an instrumental role in investigating whether Trump had sought to obstruct justice, and he was involved in the prosecutions of Michael Cohen, Trump’s former personal lawyer and fixer; Roger Stone, a longtime Trump friend; and George Papadopoulos, a foreign policy adviser to the Trump campaign. He remained on the team until the special counsel’s office formally closed last month.

Over the course of a two-year investigation, the special counsel charged 34 people, including 26 Russian nationals, and secured guilty pleas from seven, including several high-level Trump campaign and administration officials. The investigation concluded in March, and the following month the Justice Department released the office’s 448-page report documenting its work.

The report said investigators found insufficient evidence to show a conspiracy between the Trump campaign and Russia to influence the election and reached no conclusion on whether Trump obstructed justice — despite laying out a series of episodes of the president apparently seeking to stymie the investigation. Mueller’s team wrote that they were bound by Justice Department policy that forbids the indictment of a sitting president from deciding or alleging — even privately — that Trump had committed a crime.

Goldstein declined to comment on whether the team unanimously supported that analysis. “I’m not going to say one way or the other,” he said. He also declined to say whether he personally felt there was sufficient evidence to charge Trump with obstruction, were he not president, as more than 1,000 former federal prosecutors have asserted.

“I do not believe I should say anything beyond what that report said,” he said.

Goldstein described Mueller’s shop as “a small office of truly exceptional people” who worked “extremely closely with one another” on the sensitive investigation. He said he is still in contact with many of them.

“I expect to be colleagues and friends with them for the rest of my career and life,” he said.

In recent weeks, several of those who worked under Mueller have made public what they are doing next — though even those who have left government have not publicly discussed the specifics of their work. Goldstein said he “potentially” could say more in the future, but added, “I think all of us who were on the team are going to continue to be very careful and discreet in the way that we’ve been from the beginning.”

On Friday, the firm Paul Weiss announced it would add Jeannie Rhee, another senior member of Mueller’s team who had left the WilmerHale firm to work on the special counsel investigation. The Justice Department revealed this week that Michael Dreeben, a deputy solicitor general who has argued more than 100 cases before the Supreme Court and took a sabbatical to work with Mueller, would be leaving the department.

Last month, the firm Davis Polk announced it would add Greg Andres, the senior assistant special counsel who led the prosecution of former Trump campaign chairman Paul Manafort, to its litigation department in New York. The New York Times reported that Andrew Weissmann, another senior assistant special counsel who is now a fellow at New York University School of Law, is writing a book.

Mueller himself spoke briefly at a news conference last month, but he took no questions and said he hoped the appearance would be his last public comments. The House Judiciary Committee has been negotiating with Mueller to get him to testify on Capitol Hill, though he has been reluctant to do so.

Goldstein declined to say whether he thought Mueller should testify. “I don’t want to say, one way or the other, my personal view,” he said. He added, though, that he was “100 percent supportive” of the public statement Mueller made.

Goldstein also declined to say whether he would be willing to testify publicly.

“It’s premature to even consider that,” he said. He said he has no plans to write a book.

Before joining the special counsel team, Goldstein headed the public corruption unit in the U.S. attorney’s office for the Southern District of New York. He led several high-profile cases and investigations, including the corruption prosecutions of former New York State Assembly speaker Sheldon Silver and former New York State Senate majority leader Dean Skelos. He worked as a staff writer at Time magazine and as a high school teacher before pursuing his legal career.

Goldstein said his experience on corruption cases in New York “was enormously helpful in terms of the perspective that I could bring to the special counsel’s office.”

After the special counsel’s office closed, Goldstein returned briefly to the Southern District of New York. He formally left government Friday. He said his first day at Cooley is Monday, though he plans to take time off with his family over the summer and start in earnest in September.