Jennifer Williams, an aide to Vice President Mike Pence since April, is testifying on Capitol Hill Thursday about her role in the Ukraine controversy fueling the House's impeachment inquiry.

Williams, a longtime foreign service officer based in London, joined Pence's team to advise on Europe and Russia matters just as President Donald Trump's posture toward Ukraine threw the foreign policy establishment into disarray.


Williams is testifying under subpoena after the White House attempted to block her testimony, according to an official working on the impeachment inquiry. Though the White House has ordered officials to refuse cooperation with the impeachment probe, a dozen National Security Council and State Department officials have sought subpoenas to circumvent the order. Williams is the first official from Pence's office to testify.