In this weekly column "Cross-Exam," Elie Honig, a CNN legal analyst and former federal and state prosecutor, gives his take on the latest legal news. Post your questions below. The views expressed in this commentary are his own. View more opinion on CNN. Watch Honig answer reader questions on "CNN Newsroom with Ana Cabrera" at 5:40 p.m. ET Sundays.

(CNN) When the House of Representatives launched its impeachment inquiry into President Donald Trump over the Ukraine scandal, the White House decried it as "invalid" and "baseless," and ordered some subpoenaed officials not to testify to Congress. This obstructionist strategy worked once before, as the White House effectively stonewalled the House Judiciary Committee's investigation of Robert Mueller's findings on Russian election interference by instructing executive branch employees not to comply with subpoenas.

But this time, something is different. Now, some executive branch employees who had received orders from the White House to clam up chose to comply with the House's request for testimony, as required by law. By doing so, those dutiful public officials met their oath of office to uphold the Constitution and, in the process, called the White House's high-stakes bluff.

Former Ambassador to Ukraine Marie Yovanovitch defied the White House's instruction to remain silent and instead testified to the House about the efforts of Trump's counsel, Rudy Giuliani, to have her removed from her post; one House member said she gave a "gripping and emotional account of presidential abuse of power."

Trump could have tried to enforce his direction to executive branch employees not to cooperate by going to court and seeking restraining orders preventing them from testifying. But -- perhaps recognizing that his legal grounding was shaky at best -- he didn't. Trump blinked. He got caught bluffing and, when Yovanovitch and others called him, he folded.

Now that the parade of witnesses has started, Congress and the public will learn more about Trump's efforts to push Ukraine to investigate his political rivals. Bill Taylor -- the top US diplomat in Ukraine, who famously texted Sondland that it would be "crazy to withhold security assistance for help with a political campaign" -- provided devastating testimony Tuesday. In his opening statement , Taylor established clear as day that there absolutely was a "quid pro quo" of American foreign aid in exchange for Ukrainian investigations of Trump's political rivals.

Taylor's testimony reportedly has made a major impact , with one House Democrat calling it a "sea change" and another saying it "resolved any remaining doubts I may have."

Taken together, the testimony of the public officials that have testified so far paints a damning picture. Had they meekly obeyed the White House's instructions to stay quiet -- as Don McGahn Mike Pompeo and others did before -- neither Congress nor the public would have had a full understanding of Trump's apparent misuse of office and abuse of power. But by refusing to capitulate, these public servants have caused the White House's previously impregnable stone wall to start to crumble.

Now, your questions:

Greg (Missouri): Ukrainian President Zelensky claims he felt "no pressure" from President Trump's alleged quid pro quo of military aid in return for investigation of a political rival. Legally, does this matter?

Trump has defended himself by noting that Zelensky stated he felt "no pressure" while dealing with Trump over delivery of foreign aid to Ukraine. And indeed, Zelensky has said , "nobody pushed me." But even if Zelensky truly felt no pressure, it hardly matters criminally or in impeachment.

Looking first at possible crimes committed by Trump -- bribery extortion and foreign election aid -- it makes no difference in the cases of bribery or foreign election aid charges whether the other party in the transaction felt fear or pressure.

Arguably, Zelensky's state of mind is relevant only to an extortion charge, which requires "wrongful use of actual or threatened force, violence, or fear." So, at most, if Zelensky felt no pressure, it would be relevant to only one of several potential crimes. (Color me skeptical about Zelensky's claim. As a prosecutor, I dealt with many victims of mafia extortions, and the vast majority of them claimed they felt no pressure or fear -- often because they feared angering the very person who extorted them in the first place.)

On impeachment, Zelensky's "no pressure" claim should have minimal if any impact. Congress need not find a crime to impeach. Arguably, Zelensky's subjective sense of fear or pressure could be relevant to a Congressional determination of whether Trump abused power to an extent that would justify impeachment. But ultimately, the focus of impeachment should be on Trump's actions, not on Zelensky's (dubious) claim about how he perceived those actions.

Roger (Kansas): To what extent did Mick Mulvaney's public comments undercut Trump's "no quid pro quo" defense? Can the House use Mulvaney's comments against Trump?

White House chief of staff Mick Mulvaney admitted at a news conference that Trump had engaged in a quid pro quo with Ukraine by freezing nearly $400 million in foreign aid in part to pressure Ukraine into investigating Democrats. "That's why we held up the money," Mulvaney stated, before adding an indelible punctuation mark: "Get over it."

Mulvaney's comments directly contradict one of Trump and his allies' core defenses to potential impeachment: "no quid pro quo." (Note that an explicit quid pro quo is not necessary for a federal bribery charge -- which applies to either "direct or indirect" solicitation -- and that no crime is necessary at all for impeachment.)

Mulvaney's statement can be used against Trump. In a criminal case, the law permits evidence of a statement made by an opposing party's "agent or employee on a matter within the scope of that relationship and while it existed." It would be very difficult for Trump to argue that his own chief of staff was somehow not his "agent or employee" and that Mulvaney's statement -- made at a news conference, while standing in front of the official White House seal -- somehow was not within the scope of the official relationship.

Moreover, the federal rules of evidence do not apply in an impeachment proceeding. Members of the House and Senate can consider whatever evidence they deem appropriate. So, again, Mulvaney's comments undermining Trump are in play and potentially quite damaging.

Rob (Colorado): Can the President be removed for being mentally unfit? If so, how would that be approached?

The 25th Amendment -- ratified in 1967 , largely in response to the assassination of President John F. Kennedy -- establishes procedures to temporarily remove a president from office based on incapacity.

First, the vice president, joined by a majority of the President's Cabinet members, must certify in writing to the Senate president pro tempore and the speaker of the House of Representatives that the president is "unable to discharge the powers and duties of his office." The vice president then assumes the role of "acting president," at least until the president certifies in writing that "no inability exists." The president then re-assumes office, unless the vice president and a majority of the Cabinet again declare in writing that the president is unfit. In that case, the president still remains in power unless and until both houses of Congress vote by a two-thirds majority that he is unable to serve, in which case the vice president takes over.

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I do not see the 25th Amendment as a viable means to remove Trump from office. Given the language of the amendment ("unable to discharge the powers and duties of his office") and the historical record of the amendment, it seems to apply where a president is fully incapacitated, not where a president acts impulsively, irrationally or even dishonestly. And as a practical matter, the chances of Vice President Pence and a majority of the Cabinet certifying in writing that Trump is unfit -- and both the Senate and House agreeing by a two-thirds vote if Trump contests it -- are near zero.

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Three questions to watch this week:

1. What will we learn about the Southern District of New York's ongoing investigation of Rudy Giuliani, including his relationship with recently indicted associates Lev Parnas and Igor Fruman?

2. What will we learn from testimony by Taylor and other executive branch officials?

3. Will Republicans follow the lead of Sen. Lindsey Graham and keep the door open on impeachment?