Two major cases that could impact President Donald Trump’s impeachment are being argued Friday inside the Beltway.

First, the U.S. Department of Justice is appealing a federal judge’s order requiring former White House counsel Don McGahn to testify before a House committee.

The committee wants a federal appeals court to order McGahn to testify as it examines potential obstruction of justice by the president during special counsel Robert Mueller's Russia investigation. The committee says McGahn's testimony could be useful for any Senate impeachment trial.

U.S. House Democrats have drafted two articles of impeachment against President Donald Trump. House leaders are charging the president with abuse of power and obstruction of Congress. They announced the articles of impeachment on Dec. 10, 2019. A full House impeachment vote could come before Christmas. If passed, the president would face a Senate trial in 2020, a presidential election year.

A judge last month directed McGahn to comply with the House Judiciary Committee subpoena, and a Washington-based appeals court was scheduled to hear arguments Friday.

»MORE: What are articles of impeachment all about?

Last month, only days after Trump was impeached, the House Judiciary Committee held open the possibility of recommending more articles of impeachment.

Also Friday, a federal court was scheduled to hear arguments whether the Justice Department must turn over additional materials from Mueller’s investigation to the House.

Despite already impeaching Trump, the House Judiciary Committee said it still needs information from Mueller’s investigation.

»MORE: House committee raises prospect of more impeachment articles

House Speaker Nancy Pelosi still hasn't sent Trump's articles of impeachment over to the Senate, the next step in an impeachment trial.

Impeachment was established in the U.S. Constitution as a way to accuse a president of a crime and then hold a trial to determine if guilty. The first step requires a U.S. House member to introduce an impeachment resolution. The House speaker directs the judiciary committee to hold a hearing to decide whether to put the full measure to a vote by the full chamber. A majority of the committee must approve the resolution. If approved, it moves to a full vote on the House floor. If a majority of the House vot

Despite Democrats' professed sense of urgency in passing House impeachment articles against the president, Pelosi has delayed sending the charges over to the Senate and refused to name the House managers who would handle the trial until Senate GOP leaders meet her demands.

»MORE: Who are the major players in a Trump impeachment trial?

Pelosi is demanding information from the Senate on how it plans to conduct Trump’s trial and hopes to give Senate Minority Leader Chuck Schumer of New York more leverage in talks with Mitch McConnell, the Kentucky Republican who is Senate majority leader.

Signs of independence among key U.S. senators are continuing to percolate out of Washington, as Trump’s presumably pending impeachment trial will again dominate the nation’s political headlines in coming weeks.

»MORE: Anti-Trump GOP groups upping pressure on Senate Republicans

On Monday, Sen. Susan Collins, R-Maine, slammed fellow Sens. Elizabeth Warren and McConnell for making comments ahead of the impeachment trial before it's even been officially scheduled.

One of the very first things she will have to deal with is impeachment and the Senate trial.

Collins joined Sen. Lisa Murkowski, R-Alaska, in criticizing McConnell's comments in December that the Senate will work in "total coordination" with the White House in developing Trump's defense.

»MORE: More senators breaking ranks from their parties on Trump impeachment

Trump is only the third sitting president in American history to be impeached, joining Andrew Johnson and Clinton.

The two articles of impeachment by House Democrats — abuse of power and obstruction of Congress — point to Trump pressuring Ukraine to investigate 2020 political rival Joe Biden while withholding as leverage military aid the country relies to counter Russia as well as his efforts to block the House investigation.

»MORE: Which U.S. presidents have faced impeachment?

The Constitution requires a two-thirds majority in the Senate to convict in an impeachment trial, thus making Trump’s actual removal from office highly unlikely in the GOP-controlled Senate.