While the Supreme Court has never definitively ruled on the subject, the answer appears to be yes.
The question was tested during the Watergate scandal in 1974, when justices held unanimously that a president could be compelled to comply with a subpoena for tapes and documents. After the ruling, President Richard Nixon turned the materials over to prosecutors and then resigned.
Twenty-three years later, in allowing Paula Jones’ sexual harassment suit to go forward against President Bill Clinton, Justice John Paul Stevens wrote: “We have made clear that in a criminal case the powerful interest in the ‘fair administration of criminal justice’ requires that the evidence be given under appropriate circumstances lest the ‘very integrity of the judicial system’ be eroded.”
In the same case, Stevens also said that presidents have given testimony and produced documents often enough that “such interactions … can scarcely be thought a novelty.”
In 1998, independent prosecutor Ken Starr served a subpoena on Clinton that ordered him to testify about his relationship with White House intern Monica Lewinsky. Clinton soon agreed to testify voluntarily, an arrangement Starr went along with because it headed off a potential challenge to the subpoena on constitutional grounds.
That testimony led to Clinton’s impeachment on charges he lied under oath and obstructed justice. The occasion also was the first in which a sitting president testified under oath in a criminal investigation in which he was a potential target.
Whether President Donald Trump will be the second as part of special counsel Robert Mueller’s Russia probe remains to be seen. Mueller is investigating Russian meddling in the 2016 election, whether Trump’s campaign coordinated with Russia in any way and whether Trump obstructed justice after the election.
As Trump’s lawyers have negotiated with Mueller’s team over the terms of a possible interview, Mueller raised the prospect in March of issuing a grand jury subpoena for his testimony, his former attorney said. Attorney John Dowd told The Associated Press on Tuesday that Mueller’s team had broached the subject.
As the Clinton case demonstrates, the issuance of a subpoena would not mean the end of negotiations over an interview.
But if he were subpoenaed and did not want to testify, Trump could always invoke his constitutional right not to testify against himself and decline to answer questions. But that act would pose significant political risk.
“As a practical matter, the president would have the ability to refuse to answer practically any question,” said Bill Jeffress, a veteran Washington defense lawyer who was involved in Nixon’s defense. “He has to give his name, his occupation, and that sort of thing. But any questions about his official activities or campaign activities, he can just refuse to answer.”
Trump could seek a court order to quash the subpoena, though it’s not clear that he would have any success.
Jeffress said he knows of no law that would “remotely prohibit” subpoenaing a president for testimony.
“The idea that the president would be immune from testifying in a serious criminal prosecution is probably a nonstarter,” he said.