U.S. President Donald Trump’s former top aide on Russia and Europe, Fiona Hill, is expected to appear Monday for a private deposition in the House Democrats’ impeachment probe.

Hill officially left her post in the National Security Council (NSC) in August after serving about two and a half years.

Hill, however, handed over her responsibilities a week before U.S. President Donald Trump made the call to his Ukrainian counterpart Volodymyr Zelensky on July 25. She may not know much about the conversation.

Trump’s conversation with Zelensky triggered the unfolding impeachment investigation.

It is unclear if the White House will block Hill, now a private citizen, from testifying.

“The White House has opted to use executive privilege to stop officials from testifying before Congress, but it remains legally unclear if the president can force former officials who are now private citizens from testifying,” the Hill noted.

In a recent letter to House Democrat leaders, the White House said it would not cooperate with the impeachment probe. The move suggests the White House may try to block current and former officials from testifying.

Hill, described as a staunch anti-Russia hawk, was not viewed as a Trump loyalist. She worked with former British spy Christopher Steele, the author of the infamous, largely discredited anti-Trump dossier that detailed the president’s alleged ties to Russia.

The controversial Fusion GPS firm hired Steele to compile the “pee dossier” on behalf of the Democratic National Committee (DNS) and Hillary Clinton’s 2016 presidential campaign. Steele’s dossier was reportedly at the center of the Russia collusion hoax investigation by Robert Mueller.

In late September, Politico reported:

Hill also hailed from the Brookings Institution, the epitome of the D.C. establishment Trump had pointedly rejected. And she was recruited by K.T. McFarland and Michael Flynn, who were out as Trump’s top two national security officials before Hill even formally started. She had even worked with Christopher Steele, the British ex-spymaster behind the salacious dossier that rocked the early days of Trump’s presidency. National security insiders were shocked when she took the job—she was anything but a Trump loyalist (her colleagues weren’t even sure whether she was a conservative) and the Trump-Russia probe was gaining steam and in the headlines daily.

Still, the former top Russia aide left the administration on “good terms,” Politico noted.

She “helped craft responses to Russia’s malign behavior that, to many experts, are arguably even tougher than those imposed by the Obama administration,” it added.

Hill will testify Monday that “she was unaware of some aspects of the escalating Ukraine scandal,” CNN reported Friday, citing an anonymous source.

She is expected to tell congressional investigators that Trump’s private lawyer, Rudy Giuliani, and his associates pursued a “shadow policy on Ukraine,” bypassing the NSC, NBC News added, noting:

Fiona Hill, who was until recently President Donald Trump’s top aide on Russia and Europe, plans to tell Congress that Rudy Giuliani and E.U. ambassador Gordon Sondland circumvented the National Security Council and the normal White House process to pursue a shadow policy on Ukraine, a person familiar with her expected testimony told NBC News. Hill’s appearance next week before Congress has stoked fear among people close to the president, said a former senior White House official, given her central role overseeing Russia and Ukraine policy throughout most of the Trump administration.

The House Democrat chairmen conducting the impeachment inquiry have not subpoenaed Hill, NBC News pointed out.

In a letter sent to Hill on October 9, the Democrat committee chairmen pursuing the impeachment probe reportedly warned the former Russia aide:

Your failure or refusal to appear at the deposition or produce the requested documents, including at the direction or behest of the President or the White House, shall constitute evidence of obstruction of the House’s impeachment inquiry and may be used as an adverse inference against the president.

The House panel chairmen — Adam Schiff (D-CA), Eliot Engel (D-NY), and Elijah Cummings (D-MD) — are requesting Ukraine-linked documents from Hill dating back to January 20, 2017, the day Trump was inaugurated as president.

The chairmen subpoenaed Sondland after Trump blocked him from testifying. Sondland is expected to give his deposition this week.