Trump indictment updates: Trump attacks special counsel after court

Of all the federal charges that former President Donald Trump and his aide Walt Nauta face in the investigation into the alleged mishandling of top secret government documents, obstruction is one of the most serious, according to legal experts.

Claire Finkelstein, the founder and faculty director of the Center for Ethics and the Rule of Law at the University of Pennsylvania’s Annenberg Public Policy Center, noted that the obstruction charges in the indictment against Trump and his aide carry as much serious weight as the charges related to keeping the top secret documents, with a maximum penalty of 20 years in prison.

Finkelstein said an obstruction charge can cover a broad range of alleged activities, from as simple as lying to investigators, to as major as destroying evidence. But she said it all comes down to one clear allegation: that the accused deliberately interfered with an ongoing criminal investigation.

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-ABC News' Ivan Pereira

The federal indictment against former President Donald Trump alleges that he willfully retained documents containing the nation's most sensitive secrets, including nuclear programs, after he left office, showed some of them on at least two occasions and then tried to obstruct the investigation into their whereabouts.

Federal prosecutors allege that the classified documents included "defense and weapons capabilities of both the United States and foreign countries; United States nuclear programs; potential vulnerabilities of the United States and its allies to military attack; and plans for possible retaliation in response to a foreign attack."

Boxes of the documents were allegedly stored in locations around Trump's Mar-a-Lago club, including a ballroom stage and a bathroom, according to prosecutors.

Read the full indictment here:

Miami police officers on horseback, motorcycles and bicycles are moving into positions around the downtown federal courthouse, while the Federal Protective Service is positioning cars by the building's entrance.

A few supporters of former President Donald Trump are outside the courthouse, some carrying flags and others in costume. Some opponents are in the crowd, as well, including a man carrying a "Lock Him Up" sign.

All demonstrators at this point are peaceful.

-ABC News' Brian Hartman, Aaron Katersky and Mara Robles

Former New Jersey Gov. Chris Christie took aim at former President Donald Trump during a CNN Republican Presidential Town Hall Monday night, calling Trump's conduct "inexcusable" for someone who wants to occupy the Oval Office.

"He has shown himself, and I think most particularly in his post-presidency, to be completely self-centered, completely self-consumed, and doesn't give a damn about the American people, in my view, if what the American people want is in conflict with what Donald Trump thinks is best for him," Christie said.

"I mean, put aside taking the documents in the first place," Christie said. "But then when you start getting asked … nicely with a letter from the archivist saying, 'Could you please give it back,' and you ignore it, ignore it, ignore it. Then they come with a grand jury subpoena, and then, according to the indictment, you tell your lawyers to tell them we don't have anything even though you have dozens and dozens of boxes of material. That's obstruction of justice, if it's true."

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