CNN — 

At the heart of the case of “United States of America v. Donald J. Trump and Waltine Nauta” are 31 classified documents that former President Donald Trump kept at his Mar-a-Lago club, each briefly described in the indictment against him.

Trump has pleaded not guilty to the charges and given a variety of defenses for his handling of the documents.

Those 31 documents are alluded to in the indictment using an intelligence shorthand, such as one labeled: “TOP SECRET//[redacted]/[redacted]// ORCON/NOFORN” that is followed by a brief description: “Document dated June 2020 concerning nuclear capabilities of a foreign country.”

To decipher the intelligence markings of the classified documents and how sensitive the intelligence they contain might be, I turned to two of the United States’ leading experts on intelligence.

Douglas London is a retired, 34-year veteran of the CIA’s Clandestine Service with multiple postings in the Middle East, Africa and Asia, who spent much of his career recruiting agents in foreign countries and who has written a very interesting book about his experiences, “The Recruiter: Spying and the Lost Art of American Intelligence,” along with frequent contributions to CNN Opinion.

I also spoke to Mark Stout, a historian who has written or co-edited several books about intelligence and who also served for more than a decade as an intelligence analyst at the State Department and the CIA.

London and Stout walked me through what can be learned about the documents in the indictment. (You can hear excerpts of my conversations with them on my podcast, ”Decoding the Trump Indictment”) So, let’s start with the one I just mentioned, “TOP SECRET//[redacted]/[redacted]// ORCON/NOFORN. Document dated June 2020 concerning nuclear capabilities of a foreign country.”

London points out that this document about the nuclear program of a foreign country is so sensitive that even two of the codenames related to the document “have been redacted because of their sensitivity.”

The category of this document, “TOP SECRET,” is the highest category of classification, which means that releasing the intelligence in the document would do “exceptionally grave damage to the national security” of the US.

Further underlining the sensitivity of the intelligence in this document about the nuclear program of a foreign country is the notation “ORCON,” which is short for “Originator Control,” meaning that whichever US intelligence agency produced this document would need to approve before the document could be shared with any other agency within the US government, according to London. And “NOFORN” is almost self-explanatory: The document can’t be shared with foreigners.

I asked London about another document labeled “TOP SECRET//HCS-P/SI//ORCON-USGOV/NOFORN” which is described as an “Undated document concerning military activity of a foreign country.”

Having spent decades recruiting foreigners to betray their secrets to the CIA, London quickly pointed out that “HCS-P” means “Human Control System,” which is intelligence acquired from a human source, while the “P” refers to “Product.”

In other words, intelligence in the document seems to have come from a well-placed spy working for the CIA, while the “SI” in this document refers to Signals Intelligence, so the intelligence also likely involved some signals interception by the US government, for instance, from an electronic source such as a cell phone.

London said a document about the “military capabilities of a foreign country” from January 2020 marked “TOP SECRET//[redacted]/TK//ORCON/IMCON/NOFORN” once again had a classified code word which was itself so secret that it had been redacted, while the notation “TK” is short for “Talent Keyhole,” which means that the intelligence was derived by overhead imagery of some sort, likely from satellite systems.

London then explained a point I hadn’t fully considered before: “Documents are classified to protect the sources so that we can continue collecting that information and protect the sources who are doing it. The sourcing and the collection technology is usually the most sensitive aspect, not the information itself. If you find out about Iranian war plans, Russian war plans, Chinese war plans, you know how many planes, tanks and where they might attack. But the way you collected it is what’s most sensitive.”

Those must be protected, not only because a spy for the CIA could possibly be executed but also because if a spy is uncovered or a particular technical intelligence collection method is revealed, an entire stream of important intelligence might dry up – preventing the US from learning much more about potential threats to national security.

I then asked the intelligence historian Mark Stout about six of the documents in the indictment, each of which is labeled in a similar manner as both “TOP SECRET” and “SPECIAL HANDLING,” and all of which are described as being about “White House intelligence briefing(s),” that took place on two dates in 2018, three dates in 2019 and one in 2020.

Stout says these are “almost certainly a reference to either the President’s Daily Brief or to documents given to or briefed to President Trump during the President’s Daily Brief.”

The President’s Daily Brief typically concerns an issue the president is interested in or doesn’t know about already, but is so significant that potentially “his hair is going to be on fire when you tell him,” according to Stout.

Stout explained that the President’s Daily Brief is among the US intelligence community’s crown jewels, “And you don’t want foreign powers to know what the intelligence community is telling the president in a very closed meeting in the Oval Office.“

Trump stored these classified documents in various locations, including a ballroom and a bathroom at Mar-a-Lago, a resort club where, according to the indictment, tens of thousands of guests visited after Trump had left the presidency.

The cavalier way that Trump stored some of the most sensitive secrets gathered by the US government, according to London and Stout, all of which were likely gathered at significant financial cost and possibly human risk by the US government, surely disqualifies him from once again being considered to be the commander in chief whose primary duty is to the nation’s security and to keep his fellow Americans safe.

The fiasco at Mar-a-Lago that is alleged in the indictment against him suggests that Trump could care less about this fundamental duty.

An earlier version of this article incorrectly said the “P” in HCS-P stands for “proprietary,” denoting that it comes from a particularly sensitive human source operation. In fact, it stands for “product,” meaning that it is a raw, not finally evaluated intelligence report.