Lord Black of Crossharbour once famously dressed up for a Royal garden party as the Duc de Richelieu with his free-spending wife playing Marie Antoinette.

But the former Daily Telegraph chairman, who renounced his Canadian citizenship so he could enter the House of Lords, shed his aristocratic pretensions yesterday as he appeared in a Chicago court at the start of a four-month racketeering trial that will turn on the verdict of 12 ordinary men and women from the plainspoken American Midwest.

The normally bombastic press baron, who has loudly proclaimed his innocence, slipped past waiting TV cameras as he entered the court for the first time since his legal troubles began. He told reporters that he was “feeling fine” and was “reasonably” confident of acquittal.

In court he sat brooding at the defence table, often resting his forehead on his hand in contemplation. His wife, Barbara Amiel, clutching a reporter’s notebook, sat behind him in the first row of the public gallery, next to Lord Black’s daughter from his first marriage, Alana.

Lord Black refused to make any comment as he left the courtroom through a scrum of photographers at the end of the first day. He and his wife were rushed away in a white 4x4 vehicle.

Defence lawyers fear that American prosecutors will wage class warfare against the loquacious peer, who once hobnobbed with the rich and powerful and controlled the third-largest newspaper empire on Earth.

“They are going to try to make this a case of class prejudice — and I’m not,” Lord Black’s lawyer, Edward Greenspan, told The Times. “It’s not Lord Black in America. It’s Conrad Black.”

As jury selection got under way, Lord Black’s camp was seeking well-heeled citizens who might be sympathetic to a globetrotting tycoon who travelled by corporate jet and kept homes in London, Florida, New York and Toronto.

Few of the potential jurors had heard of him, although one admitted that she had begun reading a Vanity Fair story about the case. “When I have seen his picture he seems to be dressed up in a tuxedo or something,” Kathleen Gillespie said. Another potential juror said that she viewed Canada as a “socialist country”, prompting a guffaw from Lord Black.

Judge Amy St Eve repeatedly had to warn the would-be jurors that there was nothing intrinsically illegal about receiving tens of millions of dollars in compensation. “There is nothing wrong with making a lot of money,” she said.

Lord Black has pleaded not guilty to a racketeering charge more commonly used against organised crime families, as well as additional counts of fraud, money laundering and obstruction of justice.

If convicted, he faces up to 101 years in prison and a $164 million (£85 million) fine.

Because he is not an American citizen he cannot qualify for imprisonment at the minimum-security “Club Fed” prisons, but he is seeking to regain his Canadian passport, which could allow him to serve time in a Canadian jail and with earlier parole.

Jurors will hear detailed testimony about how Lord Black allegedly disguised millions of dollars in bonuses as tax-free “non-compete” payments during the sale of the company’s US publications.

But the jury may find it easier to grasp the charges stemming from the high-spending lifestyle enjoyed by Lord Black and his columnist wife.

The indictment describes how Lord Black got US-based Hollinger International to pay $1.5 million to divide his ground-floor flat on Park Avenue, where his servants lived when he stayed in the company apartment above.

The company eventually sold the upstairs flat to Lord Black for $3 million in 2000 — the same price that it had paid for it six years before, despite a property price boom and $400,000 of renovations.

As part payment, Lord Black traded the company the ground-floor flat, which he valued at $850,000 — a 70 per cent mark-up over the same six-year period — and the company continued to let his servants live there rent-free. Prosecutors say that Lord Black also got Hollinger International to pay for him and his wife to fly a 23-hour round-trip from Seattle to a holiday on the Pacific island of Bora Bora in 2001.

When his British-born wife turned 60 in 2000, the press baron also allegedly billed the company $40,000 for her $62,000 surprise party at New York’s smart La Grenouille restaurant.

Lord Black has fought unsuccessfully to prevent prosecutors introducing evidence about his wife’s spending — including $2,463 in handbags, $2,785 in opera tickets and $2,083 in jogging gear.

“For whatever reason, Barbara Amiel-Black has sometimes been a lightning rod of controversy,” his lawyers argued. “Injecting Mrs Black into the trial would be unnecessary to any real issue and would result in a circus-like sideshow.”

The judge has also ruled that prosecutors can tell the jury about some of Lord Black’s more outrageous remarks, despite objections from a codefendant that their pomposity may prejudice the jury.

The Government is expected to cite Lord Black’s memorable e-mail response to queries about his use of the company jet for the Bora Bora holiday: “I’m not prepared to re-enact the French revolutionary renunciation of the rights of the nobility.”

The trial has a colourful cast of characters, with two homespun defence lawyers battling the US attorney known as America’s toughest prosecutor — all in front of a 41-year-old woman judge dubbed one of the “superhotties” of the US judiciary by an internet blog.

Lord Black secured a special dispensation for Mr Greenspan, known as “Fast Eddie”, one of Canada’s top lawyers, to appear in the US court.

The prosecution is being overseen by Patrick Fitzgerald, the uncompromising US attorney who last week secured the conviction of the White House aide Lewis “Scooter” Libby.

The greatest clash will come when the Government’s star witness takes the stand. David Radler was Lord Black’s right-hand man for 36 years before he struck a deal with prosecutors in return for a light sentence of 29 months.

The prosecution could also call a host of American luminaries who were involved with Lord Black’s newspaper empire, including Henry Kissinger, the former Secretary of State, and Richard Perle, the former Pentagon adviser.

The claims

— That Lord Black and three former aides siphoned off $83.95 million from the company’s American arm

— That he misled the company over the value of a New York property to buy it back at a large profit

— That the company funded his extravagant lifestyle, including a trip from Seattle to a holiday on the Pacific island of Bora Bora, $40,000 towards a surprise 60th birthday party for his wife in New York and $2,083 towards her jogging gear

— That he was caught on CCTV removing 13 boxes of evidence from his Toronto office

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