Editor’s Note: In this weekly column “Cross-exam,” Elie Honig, a former federal and state prosecutor and CNN legal analyst, gives his take on the latest legal news and answers questions from readers. Post your questions below. The views expressed in this commentary are his own. View more opinion articles on CNN. Watch Honig answer reader questions on “CNN Newsroom” at 5:40 p.m. ET Sundays.

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Sen. Kamala Harris owned the stage last week during the first Democratic presidential debate, displaying keen intellect, poise under fire, quick reactions and dynamic presence. In the pressurized, high-stakes environment of the debate, Harris gained an edge over the other candidates by deploying her secret weapon: her experience as a prosecutor. And we are already seeing how potent that weapon is, as public support for Harris surged in a CNN post-debate poll.

Harris worked in law enforcement for over 25 years, starting as an in-the-trenches prosecutor before winning election as district attorney of San Francisco in 2003 and California attorney general in 2010 (the first woman and first African American to hold the latter office). As she demonstrated last week, Harris’ prosecutorial background has uniquely prepared her to excel in the debates and to thrive in the grueling campaign ahead.

Elie Honig

Debates are hard. Candidates are on an overcrowded stage. They get to speak only in short bursts. The questions are somewhat unpredictable. And pundits analyze every word, gesture and facial expression.

But criminal trials are harder. The prosecutor must convince 12 ordinary people from all walks of life of a defendant’s guilt – unanimously. Try getting any 12 people to agree on anything unanimously – what kind of pizza to order for lunch, for example – and you’ll understand how hard that is.

And the prosecutor must convince the jury beyond a reasonable doubt, the highest burden of proof in our legal system. One significant slip-up, and the case is lost. Prosecutors must question unpredictable witnesses and respond to unexpected twists, on the spot. Along the way, judges enforce strict rules of evidence and procedure, while razor-sharp defense attorneys slash away at every word out of the prosecutor’s mouth.

As such, good prosecutors learn to read an audience and to think and speak on the fly. Harris displayed the savvy of an experienced prosecutor during the first debate. She knew exactly when to hold steady and when to attack. She sensed when to ratchet up the drama – most memorably when she told her own story of being bused to school, culminating with the indelible line “that little girl was me” – and when to pull back (for example, Harris made clear that she thinks former Vice President Joe Biden is not racist or ill-intentioned, but simply out of touch). Beyond the moments of high drama, Harris stuck determinedly to her central campaign message about working for middle class families, just as a skilled prosecutor lays out and then reinforces the core theory of a case for the jury.

This is not the first we’ve seen of Harris’ considerable courtroom skill. When Attorney General William Barr testified in the Senate, Harris was effective, asking pointed questions that left Barr first pretending he couldn’t hear and then stammering about not understanding the word “suggest.” It was a prosecutor’s dream: Harris shredded Barr, and she did it calmly and politely.

Harris has come under fire for her record as an aggressive (arguably nonprogressive) prosecutor. Critics note that in the past she fought to uphold questionable convictions, advocated against abolition of the death penalty and expressed doubt about decriminalizing marijuana. Harris’ record from two-plus decades as a prosecutor is absolutely fair game for criticism, and she will need to answer tough questions about her prior work.

But Harris can also point to innovative policies she enacted – including prisoner re-entry programs, modernized police training and the use of police body-worn cameras – and she has made clear she intends to run on a progressive criminal justice platform.

Any candidate is a product of his or her experience. Harris’ long history as a prosecutor gives her a skill set, presence and perspective – in short, an edge – that few other Democratic primary candidates can match (even the ones that also served as prosecutors). And the prospect of facing off against an unflappable courtroom tactician like Harris should be keeping President Donald Trump awake at night, too.

Now, your questions

Nadia, California: When Mueller testifies, does he have to stay within the four corners of his written report, or can he say things that are not covered in his report?

Mueller does not want to testify beyond the substance of his report – “the report is my testimony,” he stated in May – and Trump’s personal attorney Jay Sekulow claimed it would be “inappropriate” for Mueller to testify to anything beyond the report. Both are wrong.

This is not how subpoenas work. Subpoenas are mandatory, not optional. Witnesses testifying under subpoena do not get to pick and choose what they do and do not feel like answering. Mueller of all people knows this: he served over 2,800 subpoenas during his investigation, and the utility of those subpoenas depends largely on their compulsory nature. Nor can outside attorneys for potentially aggrieved parties (like Sekulow) impose self-serving, arbitrary limits on the testimony.

There are some questions that Mueller can appropriately and lawfully decline to answer, including those relating to ongoing criminal investigations and sensitive national security issues – largely due to the need for ongoing confidentiality.

As a practical matter, however, if Mueller declines to answer anything beyond the report, there is little that House committee members can do. The committee can go to court to compel Mueller to answer, but that process would be time consuming and burdensome. It would hardly seem worth the trouble and controversy, particularly if Mueller only declines to answer a few questions.

Mueller has serious questions left to answer, within and beyond his report, in which he decided to take a cautious, ambiguous and at times indecipherable approach to describing his findings. Most pointedly, he left unclear whether he found sufficient evidence that Trump committed obstruction of justice. If Mueller refuses to answer fully as the law requires, he will do a disservice to his investigation, his legacy and the American public.

Chris, Pennsylvania: According to federal law, nepotism is illegal, so why isn’t anyone pressing this issue against Trump’s appointment of his children to high-ranking positions?

Federal law does prohibit nepotism, defined as the hiring by the President or other senior officials of a family member to an agency over which he or she has jurisdiction. But the Department of Justice in 2017 opined that the law does not apply to White House staff – giving Trump the green light to hire family members as White House advisers. Trump used the Justice Department’s end-around to name his daughter Ivanka Trump “adviser to the President.” Similarly, Trump’s son-in-law Jared Kushner is “senior adviser to the President.”

Controversy arose when Trump brought Ivanka Trump to the G20 summit and had her provide a “readout” of Trump’s meetings with other world leaders. The absurdity of Ivanka Trump – who never worked in foreign affairs before her father became President – attempting to conduct high-stakes foreign relations with other world leaders underscores the need for anti-nepotism laws. But until Congress closes the loophole for White House staffers, or the Justice Department amends its opinion permitting the hiring of such personnel, we run the risk of giving undue power to underqualified relatives of top federal officials.

Sam, Hawaii: Doesn’t Congress have some inherent contempt authority to arrest people who disobey its subpoenas?

With Trump administration officials repeatedly defying congressional subpoenas, House Judiciary Committee Chair Jerrold Nadler has vowed that he will file lawsuits seeking to compel testimony from Barr, former White House counsel Don McGahn, former White House aide Hope Hicks and others. If Nadler succeeds, courts will order the witnesses to comply with the subpoenas and testify.

But the law also gives Congress its own inherent enforcement powers, separate and apart from the courts, to arrest and imprison witnesses held in contempt for defying a subpoena. Despite the antiquated title, there actually is a House Sergeant-at-Arms – Paul Irving, a former Secret Service agent – who is “the chief law enforcement and protocol officer … and is responsible for maintaining order” within the House. While there currently is no functioning jail on the Capitol grounds, there are several rooms inside the Capitol building that historically were used to imprison people held in contempt.

Like the Capitol jail, however, Congress’ inherent contempt authority is now a curious relic. House Speaker Nancy Pelosi recently referenced the House’s contempt powers, jokingly threatening to arrest and imprison administration members who defy congressional subpoenas. Indeed, Congress has not exercised its inherent contempt authority since 1935. There is no particular legal reason why Congress’ inherent contempt authority has effectively disappeared; it simply has gone dormant over many years of non-use.

Chris, New York: How is it that the Supreme Court ruled this term that a person can be prosecuted twice, once by a state and once federally, for the same offense? Doesn’t this violate double jeopardy?

The Fifth Amendment of the Constitution does prohibit double jeopardy: no person shall be “subject for the same offense to be twice put in jeopardy.” But the Supreme Court ruled last month in Gamble v. United States that it does not violate double jeopardy for the same person to be tried for the same conduct in two different jurisdictions. The court ruled that, as long as the two prosecutions are brought by “separate sovereigns” – in Gamble’s case, the state of Alabama and then the federal government – there is no double jeopardy problem. If, however, a person is charged twice by the same sovereign for the same crime, then double jeopardy bars the second prosecution.

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    The decision crossed traditional ideological lines between conservative and liberal justices. Seven of the nine justices – John Roberts, Clarence Thomas, Stephen Breyer, Samuel Alito, Sonia Sotomayor, Elena Kagan and Brett Kavanaugh – comprised the majority. Ruth Bader Ginsburg and Neil Gorsuch, who usually stand far apart on the ideological spectrum, dissented.

    The Gamble decision is bad news for former Trump campaign chair Paul Manafort, who was convicted in federal court and then charged in New York court with crimes relating to some of the same conduct as his federal conviction. There is now no question that the New York prosecution can continue and does not violate double jeopardy.

    Three questions to watch for next week:

    1) What caused Trump to lash out at the New York attorney general in tweets on two consecutive days? Was he informed that bad news might be coming?

    2) When will Nadler make good on his continued declarations that the House Judiciary Committee will go to court to enforce its subpoenas?

    3) How will the D.C. District Court respond to the House Ways and Means Committee lawsuit seeking to compel Trump to release his tax returns?