WASHINGTON DC — Former President Donald Trump has been charged with mishandling hundreds of classified documents, including about US nuclear secrets and military plans.

The 37-count indictment accuses him of keeping the files at his Florida estate, including in a ballroom and a shower, and lying to investigators.

It alleges he then tried to obstruct the investigation into the handling of the documents. Trump, who is running for president again in 2024, denies any wrongdoing.

But legal experts say that the criminal charges against Trump could lead to substantial prison time if he is convicted.

Charges have also been filed against Walt Nauta, a personal aide to Trump. The former White House military valet is accused of moving files to hide them from the FBI.

The 49-page indictment contains the first-ever federal charges against a former US president. It says the classified documents Trump stored in his boxes contained information about:

• United States nuclear programs.

• Defence and weapons capabilities of both the United States and foreign countries.

• Potential vulnerabilities of the United States and its allies to military attack.

• Plans for possible retaliation in response to a foreign attack.

Prosecutors say that when Trump left office, he took about 300 classified files to Mar-a-Lago — his oceanfront home in Palm Beach, which is also an expansive private members’ club.

The charge sheet notes that Mar-a-Lago hosted events for tens of thousands of members and guests, including in a ballroom where documents were found.

Prosecutors said Trump tried to obstruct the FBI inquiry into the missing documents by suggesting that his lawyer “hide or destroy” them, or tell investigators he did not have them.

“Wouldn’t it be better if we just told them we don’t have anything here?” Trump said to one of his attorneys, according to the indictment.

Trump’s first court appearance in the case will be in Miami, Florida, on Tuesday — the eve of his 77th birthday.

Mar-a-Lago “was not an authorized location” for classified documents to be kept or discussed, the indictment says.

Some files were allegedly stored on stage in the ballroom, where events and gatherings took place — and later in a bathroom and a shower, an office space, and in Trump’s bedroom.

On two occasions in 2021, the former president allegedly showed classified documents to people without security clearance, including a writer and two members of staff.

At his golf club in Bedminster, New Jersey, which was also an “unauthorized location”, he is said to have displayed and described a “plan of attack” that he told others had been prepared for him by the Department of Defense.

“As president, I could have declassified it. Now I can’t, you know, but this is still a secret,” Trump allegedly said, according to an audio recording.

Prosecutors say Trump then showed off classified documents again in August or September 2021 at the Bedminster club.

The former US president allegedly “showed a representative of his political action committee who did not possess a security clearance a classified map”.

This map “related to a military operation” and Trump told the person “he should not be showing it” to them and they “should not get too close”, the indictment says.

Special Counsel Jack Smith, who is overseeing the investigation, said on Friday that laws protecting national defense information were critical and must be enforced.

“We have one set of laws in this country, and they apply to everyone,” he said in a brief statement in Washington.

In a social media post, Trump blasted Smith as a “deranged lunatic”.

“He is a Trump hater — a deranged ‘psycho’ that shouldn’t be involved in any case having to do with ‘Justice,’” he wrote on his Truth Social platform.

Trump pointed out that classified files were also found in President Joe Biden’s former office and Delaware home, including in his garage.

The White House has previously said it immediately cooperated with officials as soon as those files were discovered, contrasting with Trump’s alleged efforts to obstruct investigators.

A federal investigation into Biden’s handling of classified documents is being led by Special Counsel Robert Hur and is still under way.

Shortly before the Department of Justice made the criminal charges public, two of Trump’s lawyers suddenly quit the case without much explanation, saying this was a “logical moment” to resign.

This is the second criminal case for Trump, who is due to go on trial in New York next year in a state case involving a hush-money payment to a porn star. — BBC