The House Judiciary Committee kicks off its first hearing of the impeachment inquiry at 10 a.m. Wednesday with an exploration of the constitutional grounds for impeachment, including what constitutes bribery, high crimes and misdemeanors and whether President Donald Trump's actions meet those definitions.

The witnesses will include Harvard law professor Noah Feldman; Stanford law professor Pamela Karlan; University of North Carolina law professor Michael Gerhardt; and George Washington University law professor Jonathan Turley. The first three witnesses were asked to testify by the committee's Democrats, and Turley was called by the panel's Republican members.

The White House refused an invitation to Trump and his lawyers to participate, but it has not ruled out the possibility of taking part in future hearings.