Donald Trump has pleaded "not guilty" to 37 charges of mishandling government secrets and scheming to prevent their return.
He faces the charges after removing classified documents upon leaving office and failing to give them up to the National Archives.
The US government accuses him of violating the Espionage Act and other laws.
Trump is vying to win back the White House next year and has dismissed the charges as "ridiculous." The runaway frontrunner in the 2024 Republican primary has vowed to stay in the race regardless of the outcome of the documents case.
Donald Trump, the former US president, faces multiple criminal probes and could face trial in multiple cases as he campaigns for reelection.
He has praised the rioters who ransacked the Capitol to halt the certification of the 2020 election and has promised pardons for many if he is reelected.
Trump vowed to appoint a special prosecutor to investigate President
Joe Biden and his family.
Republican leaders in Congress and Trump's rivals for the party's presidential nomination have largely ignored the allegations against Trump and instead attacked the Justice Department.
A pro-Trump super PAC launched an ad noting that an investigation into Biden's handling of classified documents has not yielded an indictment.
The two cases bear few similarities as Biden is not accused of refusing to return classified documents or suspected of thwarting government attempts to recover them.