President Trump has used Twitter to speak out against lots of people—and now special counsel Robert Mueller is scrutinizing the president's tweets about Jeff Sessions and James Comey, three sources tell the New York Times. Sessions and Comey are key witnesses in Mueller's investigation into Russian interference with the 2016 US presidential election, and some of Trump's tweets against them came as he was also privately putting pressure on them about the probe. Mueller, the sources say, is looking into whether Trump was trying to obstruct the special counsel investigation via pressure and intimidation, and they say he wants to question Trump about the tweets. The Times explains that this is different from most obstruction cases, in which evidence is typically made up of private actions like destroying evidence.
Mueller has also shown interest in Trump's private interactions with Comey, Sessions, and others; misleading statements from the White House; Comey's firing; and possible offers to pardon witnesses in the special counsel investigation. Trump's lawyers have publicly said none of that constitutes obstruction and Trump should not be subjected to questioning about them, but sources say privately, some of them have been concerned Trump's tweets could expose him to legal issues. Legal experts say that, lacking one clear piece of evidence, prosecutors sometimes instead look to identify a pattern of behavior. But the Times notes there are "hurdles" to making a strong obstruction case, including finding credible witnesses. Trump's lead lawyer, Rudy Giuliani, didn't sound concerned in his public statement on the latest news: "If you’re going to obstruct justice, you do it quietly and secretly, not in public." See the Times for more. (Read more Robert Mueller stories.)