Robert Mueller knows a great deal more than he put in his richly detailed 448-page report

He says so again and again right in the report.

Two crucial words he put into the report at least eight times are messages to our Congress and the rest of us about how his investigation was hamstrung by rules from telling all that he and his team learned.

Those two words: “admissible evidence.”

In testimony to Congress, Mueller will be free to tell what evidence he had, but that did not meet the standards of his charter, the Justice Department or federal court rules.

The federal courts have developed ever more detailed rules about what evidence is admissible and what is not. The Justice Department has expanded its manual for prosecutors to adapt to these rules.

Only one group has benefitted more from these rules than white-collar criminals, who have lawyers like Roy Cohn and Michael Cohen to advise them on how to lie, cheat and steal without much risk of being indicted and much less risk of being convicted.

Our federal government makes only a minimalist attempt to pursue white-collar criminals. For example, during tax season in February only 71 criminal tax cases were filed in the whole country. Most of them involved drug dealers or bribe-taking politicians, not flat out tax cheats. And there were just 52 convictions, half of the level of five years ago.

The one group that benefits more than white-collar crooks from court rules on admissible evidence are foreign agents and spies. That’s because they are beyond the reach of American law enforcement in most cases, Russian spy Maria Butina being a notable exception.

Mueller indicted 25 Russians, half of them military officers, and three Russian companies, but he has no way to bring them to trial unless they do something incredibly stupid like set foot on American soil. Capturing just one of them, and making him flip, would terrify Trump—and for good reason, based on the Mueller report findings.

Congress, however, is not burdened by the evidence rules that constrained Team Mueller.

Our Congress can go wherever the facts point. That freedom can be abused, which Trump is sure to continually complain is the case. But the freedom to look for the truth also means that Congress can see past the smoke and spot the fires causing it.

Mueller, in closed-door sessions and in public testimony, will be free to tell what evidence he had, but that did not meet the standards of his charter, of the Justice Department manual governing its prosecutors or federal court rules.

Attorney General William Barr, who lied through his teeth at his gratuitous press conference just before he gave the report to Congress, said that Mueller would be free to testify to Congress. We’ll see, but don’t count on Barr having been honest because his actions over the years show he is not honest.

The report, in the language below from Page 18 of Volume 1, is pregnant with a message to Congress about evidence he could not put in the report:

The investigation did not always yield admissible information or testimony, or a complete picture of the activities undertaken by subjects of the investigation. Some individuals invoked their Fifth Amendment right against compelled self-incrimination and were not, in the Office’s judgment, appropriate candidates for grants of immunity. The Office limited its pursuit of other witnesses and information-such as information known to attorneys or individuals claiming to be members of the media—in light of internal Department of Justice policies. See, e.g., Justice Manual§§ 9-13.400, 13.410. Some of the information obtained via court process, moreover, was presumptively covered by legal privilege and was screened from investigators by a filter (or “taint”) team. Even when individuals testified or agreed to be interviewed, they sometimes provided information that was false or incomplete, leading to some of the false-statements charges described above. And the Office faced practical limits on its ability to access relevant evidence as well-numerous witnesses and subjects lived abroad, and documents were held outside the United States.

Further, the Office learned that some of the individuals we interviewed or whose conduct we investigated-including some associated with the Trump Campaign—deleted relevant communications or communicated during the relevant period using applications that feature encryption or that do not provide for long-term retention of data or communications records. In such cases, the Office was not able to corroborate witness statements through comparison to contemporaneous communications or fully question witnesses about statements that appeared inconsistent with other known facts.

Accordingly, while this report embodies factual and legal determinations that the Office believes to be accurate and complete to the greatest extent possible, given these identified gaps, the Office cannot rule out the possibility that the unavailable information would shed additional light on (or cast in a new light) the events described in the report.

Mueller also notes, at Page 182, that his office found significant evidence of involvement with Russians linked to the Kremlin, but brought charges in only some cases because of the admissible evidence rule.

Mueller said his team “determined that the contacts between Campaign officials and Russia-linked individuals either did not involve the commission of a federal crime or, in the case of campaign-finance offenses, that our evidence was not sufficient to obtain and sustain a criminal conviction. At the same time, the Office concluded that the Principles of Federal Prosecution supported charging certain individuals connected to the Campaign with making false statements or otherwise obstructing this investigation or parallel congressional investigations.”

At Page 193 Mueller wrote that his office “considered whether to charge Trump Campaign officials with crimes in connection with the June 9 meeting…  The Office concluded that, in light of the government’s substantial burden of proof on issues of intent (‘knowing’ and ‘willful’) , and the difficulty of establishing the value of the offered information, criminal charges would not meet the Justice Manual standard that ‘the admissible evidence will probably be sufficient to obtain and sustain a conviction.’  Justice Manual§ 9-27.220.”

He explains further on the next page that “the Office did not obtain admissible evidence likely to meet the government’s burden to prove beyond a reasonable doubt that these individuals acted ‘willfully,’ i.e., with general knowledge of the illegality of their conduct; and, second, the government would likely encounter difficulty in proving beyond a reasonable doubt that the value of the promised information exceeded the threshold for a criminal violation.”

In other words, wrongful acts took place, but court rules and Justice Department policies together with missing, destroyed or unavailable (from the Kremlin agents in the meeting) evidence are too strict to make a criminal case, which requires convincing 12 jurors beyond a reasonable doubt of criminal intent.

And despite the axiom that ignorance of the law is no defense, it actually can be for white-collar crimes, as Mueller wrote at Page 194. He focuses on the word scienter, a legal term that meansknowledge of wrongdoing.

“Most significantly, the government has not obtained admissible evidence that is likely to establish the scienter requirement beyond a reasonable doubt. To prove that a defendant acted ‘knowingly and willfully,’ the government would have to show that the defendant had general knowledge that his conduct was unlawful,” Mueller wrote.

Think of that as the “too stupid to be guilty of a crime” defense.

Even if a fully unredacted version of the Mueller report becomes available –and it will, even if it not until some distant future day – it is vital that Mueller and his team testify before Congress.

Mueller almost shouts to us and our Congress that the full Mueller report is far from the full report on what his team learned about our president and his embrace of Kremlin help to get into the Oval Office.

We need to hear all the facts.