Now that two congressional committees have subpoenaed Special Counsel Robert Mueller to testify, what are the key questions for him? Mueller will appear on July 17 to testify before the House Judiciary and Intelligence Committees in open and closed sessions. Here are some questions for the committees to ask.

1. What do we need to know to safeguard our elections from Russia in the future?

Mueller’s most important conclusion in his report was that Russia interfered with our election in “sweeping and systematic fashion.” What are the lessons learned about its social media propaganda campaign and hacking operation that we could use to disrupt such efforts in the future?

The report also states, “Victims included U.S. state and local entities, such as state boards of elections (SBOEs), secretaries of state, and county governments, as well as individuals who worked for those entities. The GRU also targeted private technology firms responsible for manufacturing and administering election-related software and hardware, such as voter registration software and electronic polling stations.” Did the attack impact the outcome of the election? What steps should we take to harden our election infrastructure? Classified aspects of the investigation can be addressed during the closed session.

Mueller’s report states that President Trump attempted to have then-Attorney General Jeff Sessions reverse his decision to recuse himself from the investigation and publicly announce that the investigation would focus on future elections only. If Trump had been successful, he would have prevented Mueller from learning about how Russia attacked our presidential election in 2016. What lessons about the attack that would remain unknown if this attempt to obstruct the investigation had been successful?

2. What were the key findings of your investigation?

During his press remarks, Mueller said that his report is his testimony, but it is clear that many people have not read or absorbed the substance of his report. His testimony is an opportunity to inform the public about some of his key findings. Even if he merely highlights some of his factual determinations, his testimony will raise public awareness about hundreds of links between Russia and the Trump campaign and obstructive conduct to conceal them. Attorney General William Barr seized the narrative when he published his own summary of the report three weeks before its public release, and announced that the special counsel found no “collusion” during his public remarks on the day the report was released, parroting Trump’s terminology.

In fact, the report describes troubling incidents of communicating with Wikileaks about the release of stolen email messages, sharing polling data with Russian intelligence, meeting with Russians for the purpose of receiving “information and documents that would incriminate Hillary” Clinton as “part of Russia and its government’s support for Mr. Trump,” among others. Mueller’s description of these events would raise public awareness of these incidents. While these acts may not have amounted to the technical crime of conspiracy, they demonstrate a lack of loyalty to the United States that should trouble every American.

3. How was your investigation impeded?

While Barr has stated that the White House was “fully cooperative with the Special Counsel’s investigation,” Mueller’s report tells a different story about members of the Trump campaign and Trump himself. He wrote that “the investigation established that several individuals affiliated with the Trump Campaign lied to the Office, and to Congress, about their interactions with Russian-affiliated individuals and related matters. Those lies materially impaired the investigation of Russian election interference.” He further noted that some witnesses provided incomplete information, deleted text messages, and used encrypted messaging apps that prevented Mueller from discovery all relevant information. Trump himself refused to sit for an interview. Other witnesses invoked their Fifth Amendment rights against self-incrimination, and while they have a constitutional right to do so, they cannot accurately be described as “fully cooperative.”

4. What were the “gaps” in your investigation?

Mueller wrote that in light of these “identified gaps,” in the evidence, “the Office cannot rule out the possibility that the unavailable information would shed additional light on (or cast in a new light) the events described in the report.” Uncooperative witnesses, legal privileges and documents and witnesses located overseas, beyond the reach of grand jury subpoenas, impeded the investigation, according to the report. What questions remain as a result of these gaps in the evidence?

“ Did Barr ask you to end the investigation before you thought it was ready? ”

For example, the report says that one area that Mueller’s team was unable to fully understand was the sharing of polling data by former campaign chair Paul Manafort to Konstantin Kilimnik, whom the FBI assesses is connected to Russian intelligence. The polling data included information about Michigan, Wisconsin, and Pennsylvania, three states in which Trump won upset victories on election night. Mueller could point the committees toward a path for obtaining information to fill those gaps in his investigation.

5. Why did Mueller not pursue an in-person interview of Trump?

Mueller attempted unsuccessfully to arrange for an interview with Trump for more than a year. He wrote that an interview of Trump was “vital” to his investigation, and “in the interest of the Presidency and the public for an interview to take place.” Trump refused to participate in an interview and instead submitted responses to written questions. Even then, he responded only to questions about conspiracy, refusing to answer questions about obstruction. More than 30 times, Trump responded that he did not recall or remember. Mueller’s report describes these responses as “inadequate,” “incomplete” and “imprecise.” Why did he let Trump off the hook?

6. Did Barr ask you to end the investigation before you thought it was ready?

Mueller investigated for 21 months before Barr became attorney general. Three weeks later, the investigation ended. Barr was Trump’s nominee for attorney general after he fired Sessions and complained that he wanted an attorney general who could protect him. Last year, Barr sent an unsolicited memo to the Department of Justice, expounding a legal theory that a sitting president can never obstruct justice as a matter of law, a theory that Mueller rejected.

Mueller ended his investigation even though 14 investigations remained ongoing, the president was not interviewed, the trial of Roger Stone had not occurred, and grand jury matters involving Stone associate Andrew Miller and an undisclosed foreign entity remained unresolved. Why did he end the investigation without completing those tasks? Were there other tasks he would have liked to have completed?

7. Why did you send a letter to the attorney general stating that his letter “did not fully capture the context, nature, and substance of this Office’s work and conclusions.”

Barr’s initial letter stated that “[T]he investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities.” Barr omitted the first part of that sentence from Mueller’s report, which stated, importantly, “Although the investigation established that the Russian government perceived it would benefit from a Trump presidency and worked to secure that outcome, and that the Campaign expected it would benefit electorally from information stolen and released through Russian efforts…”

What did you have in mind when you wrote the letter to Barr? What aspects of the context, nature, and substance of his work and conclusions did Barr’s letter fail to capture?

With regard to obstruction of justice, Barr’s letter stated that Mueller “leaves it to the Attorney General to determine whether the conduct described in the report constitutes a crime,” and then concluded that it did not. Did Mueller intend to leave it to the attorney general to decide or did he have something else in mind when he said he did not want to “preempt constitutional processes for addressing presidential misconduct” (that is, impeachment)?

8. You wrote that you were bound by the DOJ opinion that a sitting president cannot be charged, but you sought to “preserve the evidence.” What are all of the purposes for preserving evidence?

Mueller wrote that other individuals could be charged, and, in fact, were charged. He also wrote that a president can be charged after he is no longer in office. Did he also preserve the evidence so that the information could be used by Congress to pursue impeachment?

9. If Trump were not a sitting president, do you believe that the evidence would amount to a crime of obstruction of justice?

Mueller’s report describes ten separate episodes of obstructive conduct. The essential elements of obstruction are an obstructive act, a nexus to an official proceeding, and a corrupt intent. He found “substantial evidence” for each and every element with regard to four of those episodes–directing White House Counsel Don McGahn to fire Mueller, asking McGahn to falsely deny reports about that order and to create a false document consistent with the false denial, asking Corey Lewandowski to direct Sessions to reverse his recusal decision and then limit the investigation to future elections and attempting to influence the testimony of witnesses. Mueller wrote that his report did not “conclude that the President committed a crime,” but “it also does not exonerate him.” Mueller believed that because a sitting president could not be charged, fairness required that he not even accuse Trump of a crime. But 1,000 former federal prosecutors have signed a letter stating that if they had seen this behavior committed by any other person, they could conclude that the crime of obstruction of justice had been committed. Does Mueller agree?

10. Have you seen anything about the predication for the case that causes you to believe that it is necessary to investigate the investigators?

Barr has stated that he believed that “spying” on the Trump campaign occurred, that he has “not gotten answers that are … satisfactory” and that some of the facts that he has learned “don’t hang together with the official explanation of what happened.” Did Mueller see anything in his work to suggest that there is merit to Barr’s criticisms? Was the FISA process abused in any way? To what extent was the Steele dossier relied upon? Was any reliance inappropriate? Has the dossier been discredited or verified?