Donald Trump found responsible for fraud 1:38

New York (CNN) -- Former President Donald Trump appeared in a Manhattan courtroom for the first day of the civil trial in New York against him and his company of the same name, attacking at all times the judge of the case and the attorney general of New York.

Trump's appearance turned the court into an extension of the election campaign, in which he has lashed out at the four criminal charges against him and, now, against a civil case in which Judge Arthur Engoron ruled last week that Trump and the other defendants were responsible for fraud.

  • Trump Organization Found Guilty of All Tax Fraud Charges Against It

Inside the courtroom, Trump's lawyers also argued with the judge as opening statements began, a sign that they are likely to take a combative approach in a process the judge expects to last until December.

Here's what to know about what happened on the first day of Trump's trial:

Trump turns courthouse into campaign rally

Trump's arrival at the midtown Manhattan courthouse Monday morning turned the event into a self-created spectacle. Although he did not have to appear, the former president took the opportunity to strengthen his presidential campaign.

The New York prosecutor's case is civil, not criminal, but it threatens his business in New York, and Trump's appearance underscored that he considers it as urgent as the other cases against him opened in other state and federal courts.

Former President Donald Trump is attending the trial against him, his adult children, the Trump Organization and others in a civil fraud case brought by state Attorney General Letitia James. Credit: Brendan McDermid/Pool/Reuters

On camera and social media, Trump attacked New York Attorney General Letitia James for bringing the case against him. He attacked the judge over last week's sentence. And he tried to tie them to special counsel Jack Smith's criminal allegations, though they are unrelated.

"This is about election interference, plain and simple," Trump said before entering the courtroom. "They try to hurt me so that I don't do as well as I'm doing in the elections."

When he left the room on a lunch break, Trump returned to the cameras in the hallway, twice, to lash out at what he had heard. Trump attacked the judge as an "operative" and said he should be barred for ruling against him.

Asked why he appeared in person Monday, Trump repeated a familiar refrain: "Because I want to personally see this witch hunt."

Attorney General Calls for Ban Trump from Doing Business in New York

New York Attorney General Letitia James arrives outside the New York Supreme Court ahead of former President Donald Trump's civil business fraud trial Monday in New York. Brittainy Newman/AP

The Attorney General's Office made it clear Monday that it plans to go for the jugular.

U.S. Attorney Kevin Wallace urged the judge in his opening statement to ban Trump, who rose to fame and power for 50 years with a real estate empire, from doing business in New York.

Wallace alleged that Trump and his co-defendants conspired to commit persistent and repeated fraud and that Trump's financial statements convinced the banks to take hidden risks "worth hundreds of millions of dollars."

"While it may be one thing to overdo it for Forbes magazine... it can't be done while conducting business in New York State," Wallace said.

The opening statement underscored the risk the case poses to Trump and the Trump Organization, the former president's New York businesses, where Trump built his name and image before launching the political campaign that landed him in the White House in 2016.

James filed the $250 million lawsuit last September, alleging that Trump and his co-defendants committed fraud by inflating assets in financial statements to obtain better terms on commercial real estate loans and insurance policies.

  • The Trump Organization tries to decipher the future of its business after the fraud ruling in New York

Last week, Engoron ruled that Trump and his co-defendants were liable for "persistent and repeated" fraud. Trump and his companies could be forced to pay large sums in damages for the profits they allegedly made from their fraudulent business practices.

In the trial that began Monday, Engoron will study how much the Trumps and their companies will have to pay, and whether they could be barred from conducting real estate transactions in New York or borrowing from New York banks.

Prosecutors are seeking to prove six other charges, including falsifying business records, issuing false financial statements and insurance fraud.

Trump's lawyers say this is how real estate works

In this sketch, former President Donald Trump is seen in court in New York on Monday, October 2. (Credit: Christine Cornell)

With the former president watching, Trump's lawyers argued Monday that the attorney general's case was flawed, saying the differences in valuations were just part of the commercial real estate business.

Trump's lawyer, Christopher Kise, argued that there was no intent to defraud and that there were "no victims" in the case.

Kise referred to Deutsche Bank documents showing the bank valued Trump's net worth at $2 billion less than Trump, but still granted him the loan.

"They were anxious," he said.

"This is what happens every day in this city," he added.

Trump's lawyer, Alina Habba, also spoke during opening arguments, attacking the judge's conclusion in last week's judgment that valued Mar-a-Lago at $18 million (the judge said Monday that his sentence did not specifically value Mar-a-Lago at $18 million, but was citing Palm Beach tax records).

Habba said Mar-a-Lago would be sold for at least $1 billion.

"Value is what someone is willing to pay. Trump's properties are Mona Lisa properties," he added. "That's not fraud, it's real estate."

  • This was the first day of Trump's trial for fraud in New York

Judge argues with Trump's lawyers

After Habba finished his opening statement, in which he attacked James for campaigning by saying he would "catch Trump," Engoron hit back at Trump's lawyer.

The judge noted that the defense team had already tried to dismiss the lawsuit on the grounds that James had presented it as a "witch hunt" against Trump. He had already denied the motion, Engoron said, and his ruling had been upheld by a New York appeals court.

"So Ms. James' motivations are no longer at issue in this case, are they?" said Engoron.

The judge also argued with Habba about an accounting disclaimer from Mazars, Trump's former accounting firm. The disclaimer essentially said, "We rely on the Trump Organization," Engoron said. "That's how I read it."

"No, Your Honor," Habba responded, arguing that the Trump Organization trusted Mazars and "they are the accountants."

Trump watched intently during the discussion between Habba and Engoron.

Kise later argued that the problem with the judge issuing summary judgment is that "you haven't heard the evidence."

"It owes the defendants to hear the evidence," Kise said. "We have to at least give these witnesses a chance to take the stand."

Kise and Engoron debated whether the testimony of a valuation expert at trial would be considered evidence.

"I intend to be very patient and liberal in listening to things," Engoron told Kise.

The exchanges underscored how hotly contested the next trial will be, especially when it will be the judge, not a jury, that decides the outcome.

The trial will be long and will delve into the financial tangle

On Monday morning, Engoron confirmed that it expects the trial to last more than two months, until December 22, the Friday before Christmas.

The trial will also delve into the financial intricacies, as the New York attorney general's office and Trump's lawyers will debate financial statements, accounting practices and property valuations.

Wallace's opening statement to the prosecution referred to the financial statements and played clips of the statements with Trump's sons, Eric Trump and Donald Trump Jr., while addressing Generally Accepted Accounting Principles (GAAP).

The first witness the attorney general called Monday was Donald Bender, Trump's longtime accountant at Mazars USA. Bender has already retired from the firm and Mazars no longer prepares Trump's taxes. The firm resigned, saying Trump's financial statements should not be trusted.

Although Trump and his sons are expected to be called as witnesses in the trial — appearances sure to provide some fireworks — much of the trial will focus on the core of the accounting that is at the heart of the prosecution case that now threatens Trump's business.

-- CNN's Lauren del Valle and Aaron Cooper contributed to this report.