What's next in Trump impeachment probe: Depositions turn to White House

President Donald Trump ( Official White House photo by Shealah Craighead )

For only the fourth time in U.S. history, the House of Representatives has started a presidential impeachment inquiry. House committees are trying to determine if President Donald Trump violated his oath of office by asking Ukraine to investigate political rival Joe Biden and his family, and to investigate the country's involvement in the 2016 U.S. presidential election.

A quick summary of the latest news:

DEPOSITIONS TURN TO WHITE HOUSE

The three House committees leading the Democratic probe have scheduled several current and former National Security Council officials to testify this week behind closed doors - an attempt to get a better look inside the White House as Trump pushed Ukraine to conduct politically motivated investigations.

The officials include Charles Kupperman, a former deputy at the NSC who worked for former National Security Adviser John Bolton, and current NSC staff Tim Morrison and Alexander Vindman. Morrison is particularly key, as top Ukraine diplomat William Taylor told lawmakers in his deposition last week about phone calls he had with Morrison that described the Ukraine effort.

The committees have scheduled to hear from three other State Department and Defense Department witnesses as well as they attempt to determine whether military aid to Ukraine was held up as a condition of the investigations.

The Democrats are moving quickly - sometimes scheduling multiple depositions in one day - as they are trying to compile facts and eventually transition to public hearings. House Intelligence Committee Chairman Adam Schiff, who is leading the probes, said Saturday that the panels are making "rapid progress."

___

A WITNESS SUES

It is unclear if all of the officials will appear as Trump has vowed to obstruct the probe. So far, most witnesses have decided to testify after receiving subpoenas from the committees.

One of the witnesses, Kupperman, has taken the extraordinary step of asking a federal court who he should listen to - Congress or Trump.

After he was subpoenaed, Kupperman filed a lawsuit in federal court on Friday asking a court whether he should accede to House demands for his testimony or to assert "immunity from congressional process" as directed by Trump.

In the lawsuit, Kupperman said he "cannot satisfy the competing demands of both the legislative and executive branches." Without the court's help, he said, he would have to make the decision himself - one that could "inflict grave constitutional injury" on either Congress or the presidency.


RELATED COVERAGE:


DEMOCRATIC COURT VICTORY

A judge on Friday ordered the Justice Department to give the House secret grand jury testimony from special counsel Robert Mueller's Russia investigation , handing a victory to Democrats who want the material for the impeachment inquiry.

In ordering the department to turn over the material by Oct. 30, Chief U.S. District Judge Beryl Howell affirmed the legality of the impeachment inquiry itself. The Mueller materials could reveal previously hidden details to lawmakers about Trump's actions during the 2016 election and become part of the impeachment push.

The Trump administration could appeal the decision, however, further delaying the release of the materials.

___

WORTH WATCHING

The basics of the impeachment process are explained in under two minutes in this AP-produced animated video: