Donald Trump’s former personal attorney had a simple message for Congress on Wednesday: The president is a crook. “I am ashamed because I know what Mr. Trump is,” Michael Cohen, a fixer for Trump for more than a decade, testified to the House Oversight Committee. “He is a racist. He is a conman. He is a cheat.”

Great expectations preceded Wednesday’s hearing. Cohen did not disappoint. He shed new light on the president’s legal perils and the investigations surrounding them. He claimed that Trump, thanks to a tip from Roger Stone, had advance knowledge that WikiLeaks would publish its first trove of stolen Democratic emails in the summer of 2016. He testified that Trump manipulated estimates of his net worth to secure a loan from Deutsche Bank. And he alleged that Trump’s other lawyers changed his testimony to Congress on the Trump Tower Moscow project two years ago.

But the real value of Cohen’s public testimony was the window it offered into Trump’s world. Cohen was a key figure in the insular coterie that runs Trump’s personal and business affairs, and he’s now one of the few people ever to have defected from that group and spoken publicly about its inner workings. His testimony resembled that of a mafia enforcer who finally turned against the don.

A backbreaking road led Cohen from Trump’s orbit to a Capitol Hill hearing. He pleaded guilty to eight fraud-related charges last August, including two counts of violating campaign finance laws for paying hush money to two women with whom Trump had extramarital affairs. In December, Cohen also pleaded guilty to lying to Congress about his role in negotiating business deals in Russia for Trump during the 2016 election. He will begin a three-year prison sentence later this year. The New York state Supreme Court disbarred him on Tuesday.

Cohen adopted a penitent mien before Congress on Wednesday. “I am ashamed of my own failings, and I publicly accepted responsibility for them by pleading guilty in the Southern District of New York,” he said in his opening statement. “I am ashamed of my weakness and misplaced loyalty—of the things I did for Mr. Trump in an effort to protect and promote him. I am ashamed that I chose to take part in concealing Mr. Trump’s illicit acts rather than listening to my own conscience.” On multiple occasions, Cohen reminded lawmakers that he would not benefit from his testimony, and that it would not reduce the length of his upcoming prison sentence.