Americans are fiercely divided about one aspect of the Mueller investigation: the prospect that President Donald Trump committed a crime—such as conspiracy with Russians or obstruction of justice—and Special Counsel Robert Mueller’s conclusions, or lack thereof, concerning such potential felonies. But investigating possible criminal activity was by far not the entirety of Mueller’s investigation. The former director of the FBI was hired to supervise an ongoing FBI counterintelligence investigation. The counterintelligence probe had initially involved scrutiny of individuals associated with the Trump campaign, and expanded to include the President himself as a particular subject not only with respect to the 2016 campaign but also his continued relationship with Russia in office. We now know that Mueller has wrapped up his involvement in the investigation. We also have Attorney General Bill Barr’s letter concerning at least the backward-looking aspects of the investigation, including decisions Mueller made about prosecutions for criminal violations. But what about the counterintelligence aspects of the probe?

Where does the counterintelligence investigation now stand? What are the range of findings it may produce? And how may Congress or the public learn of its results?

In a dramatic Senate hearing in March 2017, then-FBI Director James Comey stated, “I have been authorized by the Department of Justice to confirm that the FBI, as part of our counterintelligence mission, is investigating the Russian government’s efforts to interfere in the 2016 presidential election and that includes investigating the nature of any links between individuals associated with the Trump campaign and the Russian government.” Comey added, “As with any counterintelligence investigation, this will also include an assessment of whether any crimes were committed.”

As our Just Security colleagues Marty Lederman, Asha Rangappa, and Rolf Mowatt-Larssen have long emphasized in discussing Mueller’s activities, counterintelligence investigations aren’t focused primarily on bringing criminal charges (though they can yield them). Instead, they’re about disrupting the threat to U.S. national security, for example, posed by individuals acting as agents of a foreign power. That includes ferreting out Americans who act as agents knowingly or unknowingly, and involves methods and standards of assessment different from the criminal process.

Where are the counterintelligence findings?

Earlier this week, House Intelligence Committee Chairman Adam Schiff commented on the question whether “the president or people around him [are] compromised in any way by a hostile foreign power,” and said that “doesn’t appear that was any part of Mueller’s report.” At least based on Barr’s four-page letter to Congress, Schiff appears correct. There is no clear mention in that letter of the counterintelligence aspect of Mueller’s work. And Schiff may have additional reasons, not yet public, to believe that the report presented by Mueller to Barr didn’t cover it.

That gap is understandable, even if Mueller’s report is over three hundred pages long. The regulations governing the work of a special counsel were constructed primarily with criminal investigations, rather than counterintelligence investigations, in mind. That’s why, at the conclusion of a special counsel’s work, those regulations call for a report explaining “prosecution or declination” decisions—which aren’t necessarily the culmination of counterintelligence investigations. Plus, those investigations often involve classified information, and it may have been simpler and safer for Mueller to keep that in a separate stream of work and, in turn, concluding paperwork.

Is there a second Mueller report? Who will see Mueller’s counterintelligence findings?

If the report delivered by Mueller to Barr didn’t include the counterintelligence piece of Mueller’s investigation (or included only pieces of intelligence directly relevant to the potential criminal conspiracy), where is that body of counterintelligence analysis? How else might it get shared with Congress or the public?

One possibility emerged within 24 hours of Barr’s letter going to Congress. “Senior officials” told news outlets that the FBI anticipates briefing congressional leaders on Mueller’s counterintelligence findings. Oral briefings, rather than written findings, provided in closed session may have been deemed by Mueller more appropriate given genuine classification concerns—especially if aspects of the investigation remain ongoing and transferred to a different part of the Justice Department with Mueller’s office winding down. If so, then it may be up to congressional leaders to determine how much of Mueller’s findings in this area can appropriately be shared with the American people, working with the executive branch on classification questions. Alternatively, after providing full briefings in closed sessions, Mueller or FBI officials could potentially provide less detailed, unclassified versions of such briefings in open session.

There are other possibilities, too. Perhaps Mueller has written something separate from the report called for by the special counsel regulations, and that written product is now in the hands of Justice Department officials. If so, members of Congress will surely call for it to be released at least to Congress. Or perhaps Mueller closed the counterintelligence investigation long ago and simply does not have major findings to report. That, too, should be ferreted out by continuing questions from the Hill.

All that said, we must leave room for the possibility that Mueller’s report does contain his counterintelligence findings, and that Barr’s carefully drafted letter chose to focus only on the criminal side of things.

Range of counterintelligence assessments of President Trump

Regardless of how we (or at least congressional leaders) learn more about this critical piece of Mueller’s work, what might the counterintelligence findings look like? It’s important to understand the spectrum of possibilities, which are quite different from those relevant to a criminal investigation (namely, indict or not). Let’s focus specifically on the question of President Trump himself.

Axis 1: Type of influence

Think of Mueller and the FBI’s conceivable counterintelligence findings regarding Trump along two axes.

One axis involves the level of influence Russia might have over the President.

That is an astonishing frame to invoke, we realize. Nonetheless it is the very concern that prompted the opening of a Trump-specific file in the particular investigation in May 2017 by senior Justice Department and FBI officials, including Acting Attorney General Rod Rosenstein and Acting FBI Director Andrew McCabe, who then reportedly informed the Gang of Eight, a group that consists of the majority and minority leaders of the Senate and House and top Republicans and Democrats on the Senate and House intelligence committees.

Along this axis, at one end of the spectrum is simply “none.” Perhaps Trump simply makes a lot of Russia-friendly decisions but without any apparent influence by Moscow. Another point on the spectrum might be called “unwitting agent.” This would involve Trump not trying to serve Russian interests over American interests but, without his awareness, succumbing to Russian influence exercised over him through public posturing, hidden messages, implicit incentives, psychological manipulation, indirect coercion and more. And at the far end of the spectrum would be “witting agent.” This would, of course, involve Trump consciously seeking to advance Russian interests whether out of a sense of alignment with Putin or due to leverage or personal financial gain.

Axis 2: Level of confidence

The second axis involves a confidence level. Here it helps to emphasize the intelligence aspect of such an investigation. The intelligence community tends to avoid claiming that it knows virtually anything with certainty. Instead, intelligence analysts operate along a spectrum of confidence. Their judgments can provide “low confidence,” “moderate confidence,” “high confidence,” or various markers in between. The key point is that counterintelligence findings would be less about asking a typical prosecutorial question—“can a prosecutor prove to a jury beyond a reasonable doubt that the defendant broke the law?”—and more about assigning an estimate about the existence of a state of affairs.

While we have focused here on the question presented about President Trump during his time in office, the intelligence toolkit has also been applied retrospectively to the 2016 campaign, as Comey described the core investigation in March 2017. Regardless of what lawyers and prosecutors might say about criminal wrongdoing including the mental state of various actors, intelligence analysts will seek to know whether individuals associated with the Trump campaign served as witting or unwitting agents of Russia, and how the Kremlin’s playbook in recruiting Americans may have worked or failed.

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Ultimately, we don’t know what we don’t know, and perhaps Mueller ended up concluding the counterintelligence aspect of his investigation with little to report. Whatever Mueller found, Barr’s recent letter did nothing to share it with the American people. And that, itself, is unsatisfactory as a final word on such a vital matter.