If Michael Cohen, President Donald Trump’s former personal attorney, moves to help special counsel Robert Mueller’s probe, the president would be “one witness away from a potential catastrophe,” said MSNBC legal expert Jonathan Turley. “I think the Cohen development is very serious. He’s one witness away from a potential catastrophe. If any of those five witnesses breaks and supports Michael Cohen, this is going to get real bad, real fast,’ said Turley Monday on MSNBC’s “Morning Joe.” Turley, a George Washington University law professor, was referring to five witnesses who have been granted immunity to testify in the trial of former Trump campaign chairman Paul Manafort. The professor The Trump Tower meeting would not establish that collusion had occurred, but if Trump knew ahead of time about Donald Trump Jr. and a Kremlin-connected lawyer meeting in Trump Tower in 2016, Trump Jr. would be in “serious jeopardy of a criminal charge.” “If Mueller was to go after Donald Trump Jr., I think we would see a very rapid chain of events and it would not end well for anyone,” Turley said in the interview. “I think that Donald Trump very well could match his past visceral language with similar action. He could start to fire people, and that would have a cascading effect. It would probably take us right to the doorstep of impeachment,” Turley said.