By Associated Press

WASHINGTON (AP) – An aide to Vice President Mike Pence has arrived on Capitol Hill to testify behind closed doors in the Democrats’ impeachment investigation.

Jennifer Williams’ appearance comes as higher profile witness, former national security adviser John Bolton, has so far failed to show up for his scheduled interview.

Democrats booked Bolton after other witnesses, including former White House aide Fiona Hill, testified about Bolton’s concerns over the administration’s Ukraine policy.

Democrats are investigating President Donald Trump’s dealings with Ukraine.

Williams is a career foreign service officer in the State Department who is detailed to Pence’s office as an adviser for Europe and Russia.