The tweets are evidence

Robert S. Mueller III, is scrutinizing tweets and negative statements from the president about Attorney General Jeff Sessions and the former F.B.I. director James B. Comey, according to three people briefed on the matter.

  NYT

And who would those three people be?

The special counsel’s investigators have told Mr. Trump’s lawyers they are examining the tweets under a wide-ranging obstruction-of-justice law beefed up after the Enron accounting scandal, according to the three people.

[...]

A spokesman for Mr. Mueller’s office declined to comment.

Yes, the three people would be on the Trump end of things. Mueller's team, as we know, doesn't talk to reporters or leak anything.

The investigators did not explicitly say they were examining possible witness tampering, but the nature of the questions they want to ask the president, and the fact that they are scrutinizing his actions under a section of the United States Code titled “Tampering With a Witness, Victim, or an Informant,” raised concerns for his lawyers about Mr. Trump’s exposure in the investigation.

Kind of a stupid statement. If they're using that section of the code, they don't need to explicitly say they're looking at possible witness tampering, do they? It's kind of a given, don't you think?

Several of the remarks came as Mr. Trump was also privately pressuring the men — both key witnesses in the inquiry — about the investigation, and Mr. Mueller is examining whether the actions add up to attempts to obstruct the investigation by both intimidating witnesses and pressuring senior law enforcement officials to tamp down the inquiry.

[...]

None of what Mr. Mueller has homed in on constitutes obstruction, Mr. Trump’s lawyers said. They argued that most of the presidential acts under scrutiny, including the firing of Mr. Comey, fall under Mr. Trump’s authority as the head of the executive branch and insisted that he should not even have to answer Mr. Mueller’s questions about obstruction.

No one should question the king.

Just because he has the authority to do something doesn't mean it isn't an obstruction of justice.

But privately, some of the lawyers have expressed concern that Mr. Mueller will stitch together several episodes, encounters and pieces of evidence, like the tweets, to build a case that the president embarked on a broad effort to interfere with the investigation.

Gee, whatever would give them that idea?

Mr. Trump’s lead lawyer in the case, Rudolph W. Giuliani, dismissed Mr. Mueller’s interest in the tweets as part of a desperate quest to sink the president.

“If you’re going to obstruct justice, you do it quietly and secretly, not in public,” Mr. Giuliani said.

That may be true for most people.

UPDATE: