Former President Donald Trump is expected to travel to New York on Monday, sources familiar with the matter told ABC News.

He is expected to appear in court on Tuesday at the earliest, the sources said, on what is expected to be around two dozen counts - including felonies.

The exact charges are unknown since the indictment will not be unsealed until Trump appears in court.

-ABC News’ Aaron Katersky, Katherine Faulders, John Santucci

As legal experts speculate on what charges lay inside the sealed indictment ahead of former President Donald Trump's expected surrender on Tuesday afternoon, many predict that prosecutors could try out a new legal theory to justify bringing the charges.

"This could be a novel legal theory," said Kate Shaw, a law professor at Cardozo and ABC News contributor, speculating on what charges the public could see against Trump while stressing it's unknown until the indictment is unsealed.

Read more here.

-ABC News' Libby Cathey

Former President Donald Trump has been charged with around two dozen counts, including felonies, sources familiar with the sealed indictment told ABC News.

The exact charges remain unknown since the indictment will not be unsealed until Trump appears in court on Tuesday.

The Manhattan district attorney’s office declined to comment.

The Senate sergeant at arms is warning of potential demonstration activity related to the indictment of former President Donald Trump.

"While law enforcement is not tracking any specific, credible threats against the Capitol or state offices, there is potential for demonstration activity," an email obtained by ABC News said.

Capitol Police "is working with law enforcement partners, so you may observe a greater law enforcement presence on Capitol Hill," the email said, adding that there could be "nationwide impacts to Senate state offices."

The Capitol Police declined to comment and the sergeant at arms didn't immediately respond to ABC News' request for comment.

-ABC News' Luke Barr

Trump's lawyer said on Sunday on ABC's "This Week" that he doesn't know what to expect when the former president is arraigned on Tuesday in New York City, given the historic nature of Trump's indictment.

"This is unprecedented. I don't know. I've done a million arraignments in that courthouse with celebrities and whatnot. But this is a whole different thing. We have Secret Service involved. I understand they're closing the courthouse for the afternoon. I just don't know what to expect to see," Joe Tacopina told "This Week" anchor George Stephanopoulos.

He likened the case to "persecution" and said the charges, which remain under seal, "revolved around" Trump paying money to adult film actress Stormy Daniels before the 2016 election to keep her from going public with a claim of an affair that Trump denies.

He told Stephanopoulos that he didn't know whether Trump would hold a press conference on Tuesday after he is arraigned.

"What I hope is that we get in and out of there as quickly as possible, that it's, at the end of the day, a typical arraignment," he said.

-ABC News' Tal Axelrod