When he spoke publicly about the report in May, Mueller said that the report would serve as his testimony and that he "would not provide information beyond that which is already public in any appearance before Congress." This means that despite the high stakes of today's hearings, Mueller might end up dodging more questions than he answers.

Again, I can’t get into internal deliberations. Robert Mueller

We'll be keeping track during the hearings. The chart will track each time Mueller declines or deflects a question.

Some of Mueller’s deflections

Mueller has declined to answer certain questions throughout his testimony today, and deflected or deferred answering others. His reasons include: He didn’t want to speculate, couldn’t get into internal deliberations, had answered the question in his report, or was under orders not to answer a particular question.

This sampling of the questions Mueller declined will be updated.

House Judiciary Committee Chairman Jerrold Nadler, D-N.Y.: “So President Trump's efforts to exert undue influence over your investigation intensified after the president became aware that he personally was being investigated?”

Robert Mueller: “I stick with the language that's in front of you.”

Rep. Doug Collins, R-Ga.: “Isn't it true the evidence did not establish that the president or those close to him were involved in the charged Russian computer hacking or active measure conspiracies or that the president otherwise had unlawful relationships with any Russian official, Volume 2, page 76? Correct?”

Mueller: “I will leave the answer to our report.”

Rep. Zoe Lofgren, D-Calif.: “We went through and we counted 126 contacts between Russians or their agents and Trump campaign officials or their associates. So, would that sound about right?”

Mueller: “I can't say. I understand the statistic.”

Rep. Sheila Jackson Lee, D-Texas: “And when you talk about the president's pattern of conduct, that include the 10 possible acts of obstruction that you investigated, is that correct? When you talk about the president's pattern of conduct, that would include the 10 possible acts of obstruction that you investigated, correct?”

Mueller: “I direct you to the report for how that is characterized.”

Rep. Steve Cohen, D-Tenn.: One of the key players in the June 2016 Trump Tower meeting was Natalia Veselnitskaya, who you described in your report as a Russian attorney who advocated for the repeal of the Magnitsky Act. Veselnitskaya had been working with none other than Glenn Simpson and Fusion GPS since at least early 2014. Are -- are you aware of that?

Mueller: “Outside my purview.”

Rep. Louie Gohmert, R-Texas: “When you were appointed as special counsel, was President Trump's firing of Comey something you anticipated investigating, potentially obstruction of justice?”

Mueller: “I can't get into that. That's internal deliberations of the Justice Department.”

Follow the NBC News liveblog of the Mueller testimony.