Criminal statutes cited by the Justice Department in the search of Donald Trump’s Florida estate for mishandled documents are rarely prosecuted, according to legal experts, but investigators may still be building a criminal case rather than simply retrieving classified records.

During the unprecedented search of the former president’s property, the FBI recovered 11 sets of “secret” and “top secret” records from Mar-a-Lago. Authorities were looking for evidence of potential violations of the Espionage Act, mishandling defense documents, and obstruction of justice.

Aside from recovering the documents, legal experts believe that reports of authorities questioning Trump aides about whether the documents were declassified indicate that authorities are still gathering evidence to build a potential criminal case against Trump himself.

Former federal prosecutor and senior counsel on President Bill Clinton’s Whitewater investigation, Paul Rosenzweig, also stated that prosecutors would not pursue witnesses about Trump’s alleged standing order for document declassification if a case could not be built.

“They wouldn’t be doing that if they just wanted the paper back,” said Rosenzweig, who now manages Red Branch Consulting for cybersecurity. “That means they’re attempting to shut down defenses and lock people in.”

Bradley Moss, a national-security lawyer, predicted on Friday that Trump would be indicted after reading the redacted affidavit. According to Lawrence Tribe, an emeritus professor at Harvard Law School, in order to uphold the rule, Attorney General Merrick Garland would have to prosecute Trump under the three statutes cited in the search warrant.

The investigation into Hillary Clinton’s use of private email while serving as Secretary of State was a watershed moment in how prosecutors will weigh the evidence against Trump, according to legal experts.

The FBI conducted an investigation into 30,000 Clinton emails to determine whether her system improperly transferred or stored classified information. According to then-FBI Director James Comey, the investigation discovered 110 emails containing classified information, including eight chains of messages containing “top secret” information.

However, after reviewing similar cases, Comey described Clinton’s actions as “extremely careless,” but not “grossly negligent.” Because there was no willful mishandling of information, disloyalty to the United States, or efforts to obstruct justice, Comey said no criminal charges were appropriate.

Former federal prosecutor and Columbia Law School professor Daniel Richman said the Clinton case demonstrated that the nature of the documents and how they were handled will be factors in whether prosecutors pursue a case.

Previous cases involving such charges involve high-profile leaks of documents, such as the Pentagon Papers about the Vietnam War, Wikileaks about State Department diplomatic cables, or Edward Snowden’s release of information about National Security Agency surveillance.

The government dropped its charges against Defense Department analyst Daniel Ellsberg after a mistrial that included revelations about undisclosed wiretaps and a government-ordered break-in at his psychiatrist’s office.

To avoid prosecution, Snowden fled to Russia. The US Justice Department is attempting to extradite Wikileaks founder Julian Assange from England.

Chelsea Manning, a former Army intelligence analyst, was sentenced to 35 years in prison for providing Wikileaks with a cache of State Department cables. After about six years, President Barack Obama commuted the sentence.

Former CIA officer Jeffrey Sterling was sentenced to 42 months in prison for disclosing classified information to a New York Times reporter about a covert operation providing false nuclear blueprints to Iran.

Stephen Jin-Woo Kim, a former State Department contract analyst, was sentenced to 13 months in prison for disclosing classified information about North Korea’s nuclear program to a Fox News reporter.

Former Army General and CIA Director David Petraeus was fined $100,000 after pleading guilty to a misdemeanor charge of sharing classified documents with his biographer. Sandy Berger, a former national security adviser to President Bill Clinton, was fined $50,000 after pleading guilty to the same misdemeanor of stealing classified documents and destroying copies of records.

The letter revealed that Trump was aware he possessed the classified documents sought by the archives months before the FBI search, which legal experts said could be used to demonstrate criminal intent to allegedly mishandle documents.

Barbara McQuade, a former U.S. attorney and now a law professor at the University of Michigan, said the letter illustrated Trump hadn’t been cooperative with federal authorities and that his claims of executive privilege to keep the documents confidential were wrong.