John Bolton Says He Will Testify in Impeachment Trial if Subpoenaed. President Donald Trump's former national security advisor made the statement on Monday. ... since my testimony is once again at issue ... I have concluded that, if the Senate issues a subpoena for my testimony, I am prepared to testify, John Bolton, Former National Security Advisor, via CNN. Bolton has first-hand knowledge of several of the instances that were front and center of the House's impeachment case against the president. He was not subpoenaed to testify before the House committee. Bolton's statement renews pressure on Senate Majority Leader Mitch McConnell to allow witnesses to be called during the Senate impeachment trial. Because he likely has more than enough Senate votes to acquit the president, McConnell has indicated he is seeking an expedited trial without calling witnesses. This has led to a stall in the impeachment process. . Speaker of the House Nancy Pelosi has refused to send the articles of impeachment to the Senate until both parties agree on Senate trial terms. Before releasing his statement, Bolton forewarned McConnell about his willingness to testify. . The White House received no forewarning.