Former US president Donald Trump has returned to his civil business fraud trial as a spectator, after a month of criticising the proceedings from afar.

He heaped praise on a professor who testified for his defence that financial statements at the heart of the case showed no evidence of accounting fraud.

With testimony winding down after more than two months, the Republican 2024 presidential front-runner showed up to watch his defence’s expert, accounting professor Eli Bartov, who reviewed the Trump financial statements and disputed the crux of the state’s lawsuit.

Mr Bartov, who teaches at New York University, testified that Mr Trump’s financial statements did not violate accounting principles, and he suggested that anything problematic – such as a huge year-to-year leap in the estimated value of the his Trump Tower penthouse – was simply an error.

Donald Trump
Mr Trump is devoting a lot of attention to the New York lawsuit (Eduardo Munoz Alvarez, pool/AP)

“My main finding is that there is no evidence whatsoever of any accounting fraud,” Mr Bartov said. Mr Trump’s financial statements, he said, “were not materially misstated”.

Mr Trump himself is scheduled to take the stand on Monday, for a second time. During a morning break, he lauded Mr Bartov’s testimony.

Even while campaigning to reclaim the presidency and fighting four criminal cases, Mr Trump is devoting a lot of attention to the New York lawsuit.

He has been a frustrated onlooker, a confrontational witness and a heated commentator outside the courtroom door.

Earlier in the trial, Mr Trump attended several days and spent one on the witness stand while the state was presenting its case. But Thursday marked his first appearance since the defence has been calling its own witnesses.

He watched attentively, at one point shaking his head when lawyers for Ms James’ office objected to some of Mr Bartov’s testimony.

“This is a witch hunt, and it’s a very corrupt trial,” Mr Trump said on his way into court on Thursday.

The case is putting his net worth on trial, scrutinising the real estate empire that first built his reputation, and threatening to block him from doing business in his native state.

Donald Trump speaks after arriving at the court
Donald Trump speaks after arriving at the court (Eduardo Munoz Alvarez/AP)

New York attorney general Letitia James’ suit accuses Mr Trump, his company and some executives of misleading banks and insurers by giving them financial statements full of inflated values for such signature assets as his Trump Tower penthouse and Mar-a-Lago, the Florida club where he now lives.

The statements were provided to help secure deals — including loans at attractive interest rates available to hyper-wealthy people — and some loans required updated statements each year.

Mr Trump denies any wrongdoing, and he says that the statements’ numbers actually fell short of his wealth.

He also has downplayed the documents’ importance in getting deals, saying it was clear that lenders and others should do their own analyses. And he claims the case is a partisan abuse of power by Ms James and Judge Arthur Engoron, both Democrats.

Mr Bartov testified that statements of financial condition are “only a first step in a long and complex process” of determining asset valuations and making lending decisions. Relying on them alone is “completely misleading” and anyone that does so is “likely to reach the wrong decision”, he added.

State lawyers contend Mr Trump and his co-defendants deceived lenders with his financial statements. But Mr Bartov said credit reports compiled by Deutsche Bank, which listed lower amounts for Mr Trump’s properties and net worth, showed that the bank did its own research and analysis and did not just rely on his word.

A Deutsche Bank executive testified last month that bankers viewed clients’ self-reported net worth as “subjective or subject to estimates” and often “make some adjustments”. Another executive, now retired, testified earlier that he assumed the figures in Mr Trump’s financial statements “were broadly accurate”, but that the bank subjected them to “sanity checks” and sometimes made sizeable “haircuts”.

State lawyer Kevin Wallace complained that Mr Bartov’s opinions on the bank’s approach strayed beyond his expertise, calling him “someone who’s hired to say whatever they want in this case”.

“You should be ashamed of yourself, talking to me like that.” Mr Bartov exclaimed. “I am here to tell the truth.”

Donald Trump
Donald Trump described proceedings as ‘a witch hunt’ (Eduardo Munoz Alvarez/AP)

Judge Engoron overrruled the state’s objection.

The attorney general’s office has also hired Mr Bartov as an expert in the past.

Mr Trump has regularly complained about the case on his Truth Social platform.

Going to court in person affords him a microphone — in fact, many of them, on the news cameras positioned in the hallway. He often stops on his way into and out of the proceedings, which cameras cannot record.

His out-of-court remarks got him fined 10,000 US dollars on October 26, when Judge Engoron decided Mr Trump had violated a gag order that prohibits participants in the trial from commenting publicly on court staffers. Mr Trump’s lawyers are appealing against the gag order.

Ms James has not let Mr Trump go unanswered, often — but not on Thursday — showing up at court herself when he is there and making her own comments on social media and the courthouse steps.

Lawyers in the case have been told not to make press statements in the hallway, but the former president has been allowed to do so.

While the non-jury trial is airing claims of conspiracy, insurance fraud and falsifying business records, Judge Engoron ruled beforehand that Mr Trump and other defendants engaged in fraud. He ordered that a receiver take control of some of Mr Trump’s properties, but an appeals court has held off on that order for now.

At trial, Ms James is seeking more than 300 million dollars in penalties and a prohibition on Mr Trump and other defendants doing business in New York.

It is not clear exactly when testimony will wrap up, but it is expected before Christmas. Closing arguments are scheduled in January, and Judge Engoron is aiming for a decision by the end of that month.