In his opening statement to the House Intelligence Committee, Mueller backed off his answer to Ted Lieu that implied he would've charged Trump if he could. He said he was barred from even making a judgement.
He speaks. Kind of.
Former Special Counsel (and former action hunk in #Resistance comics) Robert Mueller testified before Congress because he was subpoenaed to do so. Act one of the political theater event of the summer was before the House Judiciary Committee, ostensibly to discuss obstruction of justice.