For years, as Donald Trump was soaring from reality TV star to the White House, his real estate empire was bankrolling big perks for some of his most trusted senior executives, including apartments and luxury cars.

Now Trump’s company, the Trump Organization, is on trial this week for criminal tax fraud — on the hook for what prosecutors say was a 15-year scheme by top officials to hide the plums and avoid paying taxes.

Opening statements and the first witnesses are expected Monday in New York. Last week, 12 jurors and six alternates were picked for the case, the only criminal trial to arise from the Manhattan district attorney’s three-year investigation of the former president.

Among the key prosecution witnesses: Trump’s longtime finance chief Allen Weisselberg, who pleaded guilty and has agreed to testify against the company in exchange for a five-month jail sentence.

If convicted, the Trump Organization could be fined more than $1 million and could face difficulty in securing new loans and deals. Some partners and government entities could seek to cut ties with the company. It could also hamper its ability to do business with the U.S. Secret Service, which sometimes pays the company for lodging and services while protecting Trump as a former president.

Neither Trump nor any of his children who have worked as Trump Organization executives are charged or accused of wrongdoing. Trump is not expected to testify or even attend the trial.

Prosecutors have said they do not need to prove Trump knew about the scheme to get a conviction and that the case is “not about Donald Trump.” But a defense lawyer, William J. Brennan, said even if he’s not physically there, Trump is “ever present, like the mist in the room.”

That’s because Trump is synonymous with the Trump Organization, the entity through which he manages his many ventures, including his investments in golf courses, luxury towers and other real estate, his many marketing deals and his TV pursuits.

Trump signed some of the checks at the center of the case. His name is on memos and other company documents. Witnesses could testify about conversations they had with Trump. They are even expected to enter Trump’s personal general ledgers as evidence.

Prosecutors say The Trump Organization — through its subsidiaries Trump Corp. and Trump Payroll Corp. — is liable in part because former Weisselberg was a “high managerial agent” entrusted to act on behalf of the company and its various entities.

The Trump Organization has said it did nothing wrong. The company’s lawyers argue that Weisselberg and other executives acted on their own and that, if anything, their actions harmed the company financially.

Weisselberg, who has pleaded guilty to taking $1.7 million in off-the-books compensation, pinned blame on himself and other top Trump Organization executives, including senior vice president and controller Jeffrey McConney.

But he disagreed with the notion that the company was harmed, saying the perks actually saved the company money because it avoiding having to give raises.

Prosecutors have said they expect to call 15 witnesses, including Weisselberg and McConney, who was granted limited immunity to testify last year before a grand jury.

Judge Juan Manuel Merchan expects the trial to take at least four weeks, though a defense lawyer estimated last week that the prosecution case alone could go on for two months. Court will meet for a full day on Mondays, Tuesdays and Thursday and for a half-day on Friday. The trial is off on Wednesday so the judge can attend to other matters.