Donald Trump’s retention of documents marked classified at his Mar-a-Lago resort has aggravating factors that might support his criminal prosecution unlike the discovery of some documents also marked classified stored at Joe Biden’s former institute from his time as vice-president, legal experts said.

The US justice department has clear criteria for prosecuting people who intentionally mishandle highly sensitive government documents, and the facts of the Trump documents case appear to satisfy more elements than in the Biden documents case.

Broadly, the Department of Justice has typically pursued prosecutions when cases have involved a combination of four factors: wilful mishandling of classified information, vast quantities of classified information to support an inference of misconduct, disloyalty to the United States and obstruction.

The criminal investigation into Trump touches on at least two of those elements – obstruction, where a person conceals documents with an intent to impede a government agency, and the volume of classified materials at Mar-a-Lago – unlike the Biden case, which appears to touch on none.

The obstruction applies particularly to Trump because of his repeated refusal to fully surrender classified documents, including when he only partially complied with a grand jury subpoena issued in May demanding any classified materials, that led to the FBI search of Mar-a-Lago last August.

And Trump for months also resisted conducting a search for any classified documents that the justice department suspected were still in his possession even after the FBI seized hundreds of classified materials, only for that second search to turn up at least two more classified documents.

By contrast, the classified documents found last year at the University of Pennsylvania’s Biden Center for Diplomacy in Washington, where he was an honorary professor until 2019, were returned to the National Archives as soon as they were discovered when the office was being closed down.

The Trump documents case also significantly differs from the Biden documents case over the sheer quantity and scattered nature of classified materials that were potentially exposed in such a way as to support an inference of intentional misconduct, the legal experts noted.

Trump had kept hundreds of classified documents across his office and a storage room at Mar-a-Lago, as well as a separate storage unit in Palm Beach, Florida, compared with 10 classified documents found at the UPenn Biden Center in downtown Washington.

Taken together, the aggravating factors of Trump’s partial compliance with the grand jury subpoena – that led the justice department to believe Trump was actively concealing documents – and the number of classified materials at Mar-a-Lago make his case more perilous, the legal experts said.

“These cases typically are charged criminally only when an aggravating factor is present,” former US attorney Barb McQuade said of classified documents investigations. “The key difference with Trump is that two of the four are well met, and that is willful violation and obstruction of justice.

“The two factors that are present for Trump do not appear to be present in the Biden case, and so for that reason, I would say that these cases are very different,” McQuade said, adding that if she was the US attorney reviewing the Biden case, she would decline to prosecute the current president.

The two cases do share a notable similarity: both the Trump classified documents and the Biden classified documents were found commingled with other, non-classified materials, which can be an indicator of when a defendant would have been aware of their presence.

For Trump, the commingled non-classified materials were dated after the end of his presidency, suggesting he had access to the classified documents when he was no longer authorized. For Biden, the commingled materials were dated no more recently than 2016, when he was still the vice-president.