It now appears likely special counsel Robert Mueller has crossed what President Donald Trump has said is a clear red line by gaining access to the president's tax returns as part of a broadening investigation looking for links between Trump's business interests, his presidential campaign and Russia.

In fact, it seems almost certain the FBI–special counsel investigation has its hands on the president's tax returns.

A portion of this page is unavailable in this experience. For a richer experience, click here.

"Mueller would be engaged in malpractice if he didn't" already have access to the president's tax returns, a member of Congress on one of the congressional committees looking at Russia's interference in the 2016 presidential election told me.

In fact, people familiar with the type of investigation that Mueller is now running signal the near-certainty that Mueller has access to the president's tax returns. The purpose would be to use the tax returns as a road map to investigate potential Russian financial influence within Trump Organization limited liability companies.

"I believe Mueller has already obtained tax returns in the Russia investigation," Renato Mariotti, a former federal prosecutor in the Securities and Commodities Fraud Section of the U.S. Attorney's Office in Chicago, said on Twitter on Aug. 10. He later wrote in The Hill he often used tax returns in his own federal investigations, and that it is almost a necessity in an investigation like Mueller's. It's also done without knowledge of the subjects of the investigation.

"A federal prosecutor obtains tax returns by seeking an ex parte order from a federal judge. That means that the person who is being investigated doesn't know that the tax returns are being sought or if the judge issues the order," he said. "Basically, it's done in secret."

Mariotti also said that "the July FBI raid at the home of former Trump campaign chairman Paul Manafort tells us a great deal about the status of … Mueller's investigation."

Before taking "an aggressive, public action" like having the FBI search a subject's home, Mariotti wrote, a "typical step" federal prosecutors take in white-collar investigations is obtaining tax returns.

"A prosecutor would first take steps that can be done covertly, without the subject knowing, to gather evidence that can serve as the basis for more aggressive actions like search warrants," he wrote. "I worked with federal prosecutors who obtained tax returns in every single white-collar investigation they worked on."

Mariotti also said it ordinarily would require a senior Justice Department official to sign off on a request to the IRS for tax returns in a non-tax federal investigation. But, in this case, Mueller already has that authority.

"Mueller has authority to do so because the statute permits 'United States attorneys' to obtain tax returns and he has the power of a 'United States attorney' pursuant to the special counsel regulations," he wrote, noting that "even the tax return of someone other than Manafort" could be helpful to Mueller, and that "he could have tax return information for many individuals."

Does Mueller have the president's tax returns?

"I would be surprised if Mueller hadn't obtained some tax returns by now. The question is just whose tax returns he has," Mariotti wrote.

Bloomberg reported in late July that Mueller had expanded his probe to Trump's business interests – prompting the president's lawyers to complain that such an investigation was outside the scope of his remit and leading to considerable public speculation about the scope and direction of the special counsel's investigation. Meanwhile, Trump a day earlier pointed to Mueller examining his finances as a red line that should not be crossed.

A portion of this page is unavailable in this experience. For a richer experience, click here.

An even surer sign that such a red line has likely been crossed now, experts say, is the direct involvement of the IRS' vaunted Criminal Investigation unit – the one that once put mob boss Al Capone away on a tax conviction and has deep expertise in such matters.

The Daily Beast has reported exclusively that Mueller's team has, in fact, begun to work closely with this IRS department. Obtaining Trump's tax returns as a routine part of that inquiry is not just possible – it's likely, experts say.

"Special counsel Bob Mueller has teamed up with the IRS. According to sources familiar with his investigation into alleged Russian election interference, his probe has enlisted the help of agents from the IRS' Criminal Investigations unit," Daily Beast political correspondent Betsy Woodruff reported on Aug. 31.

"This unit—known as CI—is one of the federal government's most tight-knit, specialized, and secretive investigative entities. Its 2,500 agents focus exclusively on financial crime, including tax evasion and money laundering," she reported. "A former colleague of Mueller's said he always liked working with IRS' special agents, especially when he was a U.S. Attorney. And it goes without saying that the IRS has access to Trump's tax returns—documents that the president has long resisted releasing to the public."

Every American's personal tax information is sacred to the IRS. That includes the president of the United States. Any IRS employee is fired on the spot if they're caught even looking at someone's personal tax information outside of an audit. That, too, includes Trump's tax returns.

But, as Mariotti pointed to, there is one time-honored avenue for access to someone's personal tax records – and it doesn't require a subpoena or necessarily notifying the subject of the IRS or FBI investigation. Any U.S. attorney (or a special counsel acting under U.S. attorney powers) can request access to tax returns through an ex parte court order, and the request is nearly always handled without further review up the line at the IRS.

Now, quite obviously in this case, it would be nearly impossible for Mueller to obtain the president's tax returns without triggering an intense reaction inside the agency and the FBI hierarchy. But once the IRS' Criminal Investigation unit is involved – as appears to be the case, according to the Daily Beast's reporting – then that process is well-known, understood and compartmentalized.

A longtime congressional oversight staff director who has overseen dozens of similar investigations pointed me to this particular section in the criminal resource manual for U.S. attorneys, which describes what they need to do in order to obtain someone's tax returns as part of an FBI investigation.

"United States Attorneys may have occasion to seek access to tax information (returns and return information) for use in non-tax criminal matters," it reads. "Title 26, United States Code, Section 6103(i)(1) provides for tax information to be obtained upon the grant of an ex parte order by a Federal district court judge or magistrate judge for use in criminal investigations."

A portion of this page is unavailable in this experience. For a richer experience, click here.

Bringing in the IRS' Criminal Investigation unit makes this process even easier, and more likely. IRS officials then make those records available – without necessarily notifying anyone outside the investigating teams of the request. The FBI has that sole authority to request this of the IRS. When both the FBI and the IRS are working together, the circle is close-knit.

We may not know, for sure, whether Mueller's team has access to the president's tax returns until he takes an action publicly. Congressional oversight committees conducting their own investigations aren't likely to know, either.

Congressional access to tax return information from the IRS is quite limited, a senior congressional oversight investigator told me. Only the House Ways and Means and Senate Finance committees have the authority to look at individual tax returns from the IRS, and neither panel is involved in the congressional Russia investigations.

They're completely focused on tax reform at the moment. It's also highly unlikely any of them will seek those returns, this aide told me. "Even if they were briefed, I would assume that they would hold that information very close," the aide said.

And Trump's attorneys may have no way of knowing whether that red line has been crossed, either, even though it certainly appears likely that it has been. They, too, might be forced to wait and see how the Mueller investigation concludes.

