Sam Bankman-Fried faced his biggest test in the legal hot seat Monday, grilled by a federal prosecutor who was intent on poking holes through the FTX founder’s claims that unfortunate management mistakes, not criminal activity, were to blame for the crypto exchange’s collapse.

The fallen crypto star, testifying in his own defense in New York against fraud and other charges, began by confidently answering questions from his own lawyer, saying he had been honest with customers and investors and believed his business empire was in good financial shape. The trial proceedings shifted quickly after Assistant U.S. Attorney Danielle Sassoon began her cross-examination and sought to confront Bankman-Fried with a litany of his past public statements whose truthfulness she questioned.