The statute criminalises a broad array of conduct related to the mishandling of sensitive government records connected to the “national defence”, a term generally referring to military records that if disclosed could damage US national security.

Over the years, the law has been used as a legal tool by the Justice Department to prosecute people ranging from suspected Soviet spies to famous whistle-blowers like Daniel Ellsberg, who leaked the Pentagon Papers, and Edward Snowden, a former intelligence consultant who leaked classified National Security Agency records to reveal the existence of a domestic surveillance programme.

During the Obama and Trump administrations, some of the Justice Department’s most high-profile Espionage Act prosecutions targeted government employees who leaked classified information to the press or to the website WikiLeaks, such as former US Army Private First Class intelligence analyst Chelsea Manning and former intelligence contractor Reality Winner.

Trump ‘toast’ if classified records case proven: ex-attorney general

Manning was sentenced to 35 years in prison, though President Barack Obama later commuted her sentence, while Winner was sentenced to more than five years after she admitted to leaking a top secret report on Russian interference in US elections to the media outlet The Intercept.

WikiLeaks founder Julian Assange has also been charged under the Espionage Act, and is fighting extradition to the United States.

How does the espionage act apply to Trump?

Special Counsel Jack Smith’s office filed charges against Trump after the FBI searched the Florida resort where he lives in August 2022 and located about 13,000 government records, about 100 of which were marked as secret or top secret – the highest classification level, reserved for the government’s most closely-held secrets. Altogether, prosecutors say he improperly retained 337 classified records.

Trump has previously denied breaking the law, arguing that he declassified the records in question and that his broad presidential powers gave him the authority to disclose or declassify materials.

However, the Espionage Act itself does not explicitly require prosecutors to prove that the records themselves were classified, and neither Trump nor his lawyers have provided any evidence to suggest they were ever declassified.

Prosecutors have charged Trump with violating a section in the Espionage Act which applies to someone who has “unauthorised possession” of national defence information – the same crime to which Winner pleaded guilty.

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Donald Trump becomes first ex-US president to face criminal charges: lawyer

Donald Trump becomes first ex-US president to face criminal charges: lawyer

This section of the law makes it a crime to wilfully retain the information and fail to deliver it back to the proper US government official.

What will prosecutors have to prove to a jury?

To obtain a conviction against Trump, the government will need to prove beyond a reasonable doubt that he wilfully retained the material and failed to turn it over to the government.

Prosecutors do not need to show that Trump knew it was national defence information, but rather that a reasonable person should have known it was.

Part of the government’s evidence will likely entail laying out all the steps it took to get the records returned.

This includes a year-long effort by the US National Archives and Records Administration, which repeatedly reached out to Trump through his lawyers to request that he return missing records.

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While Trump finally agreed to send the Archives 15 boxes of material a year after leaving the White House, some of those records were marked as classified, and the boxes did not include all of the records in his possession.

Even after the Justice Department tried to retrieve the remaining records with a subpoena, Trump only handed over an additional 38 pages marked as classified.

It took a court-approved search warrant before the FBI was able to retrieve the bulk of the records that remained.

The government will also present evidence from Trump’s own lawyer, who was forced to testify to a grand jury about his communications with Trump. The indictment alleges Trump tried to get his own lawyer to lie to the government about the existence of the records, even going so far as to ask the lawyer to destroy or hide them.