It took seven years, but on a humid South Florida morning in June, Birkenfeld was finally called to account. Bulked up, with a goatee on his tan face, he was sandwiched between his two attorneys as they entered federal court in Fort Lauderdale. He looked nothing like a smuggler or, for that matter, a jet-setting private banker. He most closely resembled a once-great high-school athlete whose best days were behind him. He had, however, packed the courtroom to capacity. He was a star criminal.

A U.S. citizen, Birkenfeld had become a regular feature on Swiss news programs, because the information he promised to provide could well unwind 300 years of bank secrecy and dismantle the largest Swiss bank operating in the U.S.

When the judge, William Zloch, appeared, Birkenfeld popped to his feet. He had been cooperating with U.S. investigators for over a year from Geneva, hoping to avoid arrest by helping them build a case against UBS. But he had been charged anyway, for conspiracy to defraud the U.S. government by helping his biggest client, Igor Olenicoff, a Russian-born property developer in California, evade $7.2 million in taxes on $200 million in assets he had hidden in Switzerland and Liechtenstein. Birkenfeld was looking at a jail sentence of five years and a $250,000 fine, but had pledged in a plea agreement to cooperate formally with the U.S. government, promising to tell everything he knew about UBS’s offshore private-banking business in exchange for leniency.

Judge Zloch, a former Notre Dame quarterback, was all that stood between Birkenfeld and a lighter sentence. But before accepting Birkenfeld’s guilty plea, the judge ran him through a preliminary set of questions—name, age, education, drug use (Lipitor, 10 milligrams that morning)—until he arrived at the meat of the case against him.

“You committed these acts willfully. No one forced you to do this?” the judge asked.

“No, Your Honor.”

“Is that correct?”

“That’s correct.”

“Why did you engage in this conduct?”

“I was employed by UBS, and I was paid a large salary and incentivized to do this business,” Birkenfeld answered.

“Even though it was fraudulent.”

“Yes, Your Honor.”

Since Birkenfeld waived the reading of the indictment and the statement of facts, the most shocking details about his deeds came out later in a series of court filings that make him sound more like a spy than a banker. He put cash and valuables, the documents stated, in Swiss safe-deposit boxes. He purchased jewels and artwork with funds from secret Swiss accounts. He misrepresented funds from clients’ bank accounts as loans. He destroyed all records of clients’ offshore banking.

After a pause, Zloch asked Birkenfeld if he was concerned about what he did.