CNN reports Special Counsel Robert Mueller's team has interviewed senior policy adviser Stephen Miller, the highest-level Trump associate questioned so far who still works for the president.
Mueller, who is looking into whether the president obstructed justice, is interested in Miller's role in helping President Trump write a letter outlining his reasons for firing FBI Director James Comey. That memo, while never shared outside of Trump's inner circle, would give investigators insight into the president's unedited thoughts on Comey's dismissal:
The [New York] Times reported in September that the Justice Department had turned over a copy of the letter, which was never sent, to special counsel Robert Mueller. That memo, according to a source, was very similar to a letter written by Deputy Attorney General Rod Rosenstein that was cited as the reason for firing Comey. Rosenstein's letter criticized Comey's handling of the investigation into Hillary Clinton's private email server.
But just days after the firing, Trump said he considered the Russia probe in his decision to fire Comey.
"In fact when I decided to just do it, I said to myself, I said 'you know, this Russia thing with Trump and Russia is a made-up story, it's an excuse by the Democrats for having lost an election that they should have won'," Trump said about his decision to fire Comey in a May interview with NBC News.
Read More: Mueller interviews top White House aide (CNN)