Ex-lawyer told Trump he was 'disabled' to explain why he couldn't testify to Mueller: Woodward's 'Fear'
Press conference of Donald Trump, President of United States of America, during NATO. (Shutterstock)

Donald Trump's former attorney in the Russia investigation, John Dowd, told the president of the United States that he could not possibly testify to investigators because he is mentally incapacitated, according to Bob Woodward's new book, Fear.

The exchange reportedly happened after Trump was asked to answer mock questions for his own team to see how he performed.

"After the alleged roleplay, Woodward said that Dowd told Trump “you cannot testify, you are disabled," according to the book.

Trump had repeatedly claimed that he would be happy to testify before eventually having his lawyer, Rudy Giuliani, refuse on his behalf. That sets up a potential Constitutional crisis.

It's not the only allegation of mental disability in the book, which reveals that Trump has claimed that his own attorney general, Jeff Sessions, is mentally retarded.

Watch an interview with Woodward discussing the incident below.