Jonathan Turley, a constitutional law professor called by Republicans to testify, said he believes it's a "best practice" to hold a full House vote to open an impeachment inquiry.

"It brings solemnity and weight of the decision," Turley told Democratic Rep. Ro Khanna.

Republicans have yet to hold a formal vote. House Speaker Kevin McCarthy, despite previously stating he'd hold a floor vote, unilaterally ordered the inquiry on Sept. 12. At the time, it appeared he lacked the support from his caucus for any such measure to pass.

When pressed by Khanna if he'd advise McCarthy to change course, Turley responded: "I always said I thought it was best practice."

Whether or not a House vote is needed to launch an impeachment inquiry -- as has been tradition -- is a point of contention. Democrats have pointed to a Trump-era Office of Legal Counsel memo that stated impeachment inquiries must have sign off from the House. Meanwhile, Republicans highlighted a 2019 federal district judge decision that the Democrats were legally engaged an impeachment inquiry into former President Donald Trump despite no vote being held at the time (Democrats later did vote to formalize the impeachment inquiry).

Rep. Jamie Raskin, D-Md., has propped up a clock that is counting down to the the end-of-the-day Saturday deadline when the federal government runs out of money.

Raskin brought up the impending shutdown when he questioned law professor Michael Gerhardt, a witness called by Democrats.

"Professor Gerhardt, have there ever been an impeachment process launched in the middle of a government shutdown?" Raskin asked.

"No," Gerhardt responded.

Several Democrats have said they want to hear from Trump ally Rudy Giuliani.

Rep. Jamie Raskin put forward a motion to subpoena Giuliani and former Giuliani ally Lev Parnas for testimony about what Raskin said were their efforts to dig up dirt on the Biden family's business dealings -- and Biden's actions as then-vice president -- in Ukraine during the Trump administration.

Rep. Jim Jordan, R-Ohio, quickly moved to table Raskin's motion to subpoena both men. Republicans had the votes to kill the motion, though they seemed caught off guard by the request.

Later on, Democratic Rep. Stephen Lynch also said he wanted to hear from Giuliani as he noted none of today's witnesses have first-hand knowledge about what House Republicans have alleged about the Bidens.

"When I walked into this hearing room, my first question was: where's Rudy?" Lynch said.

University of North Carolina law professor Michael Gerhardt, a witness called by Democrats, told the committee the Constitution's founders designed an impeachment inquiry to have several safeguards -- and expressed concern that they are not be adhered to in this case.

The first safeguard, he said, is credible evidence of the commission of treason, bribery and other high crimes and misdemeanors.

"There is not, at least not that I've yet heard, such credible evidence," Gerhardt said.

"Let me give you an example of what I fear is similar to the current proceedings: Hunter Biden is arrested for speeding in a car owned by his father, and the police go after the father. I don't think that's how the law should work. I don't think that's how impeachment should work."

He also stressed the importance of judicial review, telling the panel the U.S. Supreme Court previously decided that the House Oversight Committee has to conduct an investigation for a legitimate purpose.

"A fishing expedition is not a legitimate purpose," he said.