On Monday, a federal prosecutor bombarded the disgraced crypto mogul with questions as he took the stand for a second day of testimony in federal court. Over four hours, Danielle Sassoon, the prosecutor, grilled Mr. Bankman-Fried about inconsistencies between his public statements and how he ran his crypto empire before it collapsed spectacularly in November.

Mr. Bankman-Fried, 31, wearing a light gray suit and purple tie, answered in curt “yeps” or “nos,” eschewing the sometimes-winding statements he gave at other points in the trial. Sometimes rocking back and forth in his chair, he insisted that he couldn’t remember much of what he had said publicly, including about FTX’s handling of customers deposits and the conflicts of interest that plagued his businesses.

“I’m not sure,” Mr. Bankman-Fried responded over and over, as Ms. Sassoon asked about statements he had made when he was chief executive of FTX. “I can’t recall,” he said at other points.

The cross-examination exposed cracks in Mr. Bankman-Fried’s claims, dealing a potentially serious blow to his credibility with the jury of nine women and three men who will decide his fate. On a large projector screen, Ms. Sassoon displayed statements that appeared to show Mr. Bankman-Fried saying one thing in public, then acting differently in private. After having him recount FTX’s outreach to government officials in Washington, Ms. Sassoon asked him to repeat private messages in which he used an expletive to dismiss regulators as useless.

Mr. Bankman-Fried’s testimony was the most anticipated moment of the trial, which has shined a spotlight on hubris and rampant risk-taking across the crypto industry. Once the face of crypto’s efforts to woo the public, Mr. Bankman-Fried is now widely compared to some of the most notorious fraudsters in recent history, including Elizabeth Holmes, the founder of the failed blood-testing start-up Theranos.

Taking the stand was risky. Criminal defendants usually avoid testifying so that prosecutors don’t have a chance to question them. But the first few weeks of the trial were so damaging for Mr. Bankman-Fried, as a procession of government witnesses testified that he lied to the public and stole from FTX customers, that he was left with few other options to salvage the case.

In December, federal prosecutors charged Mr. Bankman-Fried with orchestrating a sweeping scheme to steal as much as $10 billion from FTX’s customers. They said he had spent the money on extravagant projects, including venture capital investments, political contributions and luxury real estate purchases in the Bahamas, where FTX was based. Mr. Bankman-Fried was also accused of creating a secret back door in FTX’s code that allowed a hedge fund he founded, Alameda Research, to seize billions of dollars in customer funds.

He has pleaded not guilty to seven counts of fraud, conspiracy and money laundering, and could face what amounts to a life sentence if convicted.

Not long after FTX imploded, three of Mr. Bankman-Fried’s closest associates — Caroline Ellison, Nishad Singh and Gary Wang — pleaded guilty to fraud and agreed to cooperate with the government, hoping for lenient sentences. All three have testified against Mr. Bankman-Fried at the trial, telling the jury that they lied and stole for years at his behest.

Mr. Bankman-Fried took the stand on Friday to tell his side of the story. Under questioning from his own lawyer, he cast himself as a hardworking founder who was overwhelmed by his responsibilities and let major business issues go unaddressed. He denied that he had committed fraud, and blamed his colleagues for many of the problems that led to FTX’s collapse.

On Monday, it was the prosecution’s turn to ask questions. The courtroom was packed with spectators, including Mr. Bankman-Fried’s parents — the law professors Joe Bankman and Barbara Fried — and Damian Williams, the top federal prosecutor in New York. Ms. Sassoon’s mother also attended.

Ms. Sassoon focused many of her questions on Mr. Bankman-Fried’s comments in interviews, in congressional testimony and on Twitter. She pressed him on inconsistent statements he had made over the years about his famously unkempt hair, and pointed out his frequent use of private planes, suggesting that his ostensibly humble lifestyle was a public relations performance. The private flights cost a total of $15 million, Ms. Sassoon said.

She also grilled him about interviews he gave before FTX collapsed, in which he insisted that Alameda had no special privileges as a customer trading on the exchange. Over the first three weeks of the trial, the prosecution’s witnesses testified that the opposite had been true, and that Mr. Bankman-Fried had channeled billions of dollars to Alameda.

At one point, Ms. Sassoon walked to the witness stand and presented Mr. Bankman-Fried with a copy of “Number Go Up,” a new book about crypto by the Bloomberg News reporter Zeke Faux. She pointed to an interview in the book in which Mr. Bankman-Fried appeared to contradict his previous claims, acknowledging that Alameda had special privileges.

Ms. Sassoon asked if seeing the book refreshed Mr. Bankman-Fried’s memory of that acknowledgment. “No, it doesn’t,” he replied.

Eventually, Mr. Bankman-Fried, who is expected to return to the stand on Tuesday, made some concessions. He acknowledged that Alameda had a $65 billion line of credit with FTX, essentially allowing it to borrow unlimited funds. The second-largest credit line, which FTX had with another firm, was $150 million, he said.

But over and over, Mr. Bankman-Fried said he couldn’t remember various statements about Alameda and FTX that reporters had attributed to him. He didn’t read all the articles, he said, and he often objected to the reporting.

“I disagreed with basically every article written about me” after FTX collapsed, he said.

Mr. Bankman-Fried said he also couldn’t remember many of the key moments in the narrative that prosecutors had presented about the fall of FTX. He said he did not recall telling former colleagues to transfer to Alameda some of the $2 billion that FTX had raised from venture capital firms. Prosecutors have charged that Mr. Bankman-Fried misappropriated money from FTX’s venture investors as well as its customers.

At one point, Ms. Sassoon asked Mr. Bankman-Fried whether he recalled making statements about the importance of safeguarding customer funds. He hemmed and hawed, eventually saying he couldn’t remember.

“I made a lot of public statements,” he said.

Then Ms. Sassoon showed the jury a tweet that Mr. Bankman-Fried had posted about that exact issue.

“And, as always, our users’ funds and safety come first,” he had written.

Sassoon, the prosecutor, asked Bankman-Fried if he knew in June 2022 that Alameda was not going to be able to pay its debt to FTX. “I did not at that time think the odds of that were significant,” he said.

This is significant because Bankman-Fried testifed on Friday that he was not aware that Alameda owed some $8 billion to FTX until October, which is months later than others have already testified at the trial.

Bankman-Fried says he never told Ryan Salame, a former top FTX executive who has pleaded guilty but isn't cooperating with the government, to transfer money raised from venture capital firms to Alameda. “I have no memory of that,” Bankman-Fried said, in what is effectively a denial that FTX's investor money was misused.

One of the allegations made by prosecutors is that Bankman-Fried misappropriated money raised by FTX from investors, along with the misappropriation of FTX customer money.

Why not? Everyone (or every juror) can see a hairdo and relate. Cryptocurrency, not so much.

Besides, from the beginning it was by Mr. Bankman-Fried’s hair that so many knew him. The wild halo of dark curls that looked as if it had never met a brush and, according to Michael Lewis in “Going Infinite,” his new book about Mr. Bankman-Fried and FTX, resembled “the hairdo of a lunatic.” The hair that suggested Einstein, electric sockets and some sort of giant brain underneath.

The hair that, along with the wrinkled cargo shorts and T-shirts that were Mr. Bankman-Fried’s everyday uniform, suggested “the ultimate billionaire white boy tech flex: I’m so above convention,” as Scott Galloway, an investor, podcast host and professor of marketing, once told The New York Times.

The hair that played into all of our subconscious associations about tech world geniuses whose move-fast-and-break-things ethos could not be constrained by old rules about personal hygiene and professional wardrobe because … hey! they clearly knew things we do not.

But now the hair is no more. Instead, Mr. Bankman-Fried has the coiffure of a mathletics kid. With his new look, the defendant, otherwise housed in the Metropolitan Detention Center in Brooklyn and reduced to wearing a jail jumpsuit, models one of three suits and one of four dress shirts bought on his behalf on sale at Macy’s for trial purposes after agreement from the judge. (Given the FTX bankruptcy, there is a limited budget.) Also, Rockports, the kind that slide on and don’t involve shoelaces — since you can’t have shoelaces in prison — and one of three ties lent by an acquaintance.

Without the hair, in his playing-by-the-rules get-up, Mr. Bankman-Fried seems kind of … average. This guy — a criminal mastermind? Look at him! He looks like the nerd next door. He clearly did not intend to defraud his investors. He is trying hard to obey the rules. He’s going to, in the words of the George Thorogood song, “get a haircut and get a real job.”

Even in courtroom sketches, the only visual record of the trial because the judge does not allow cameras in the courtroom, the just-like-us transformation comes through.

Shearing hair has long been a means of punishment for men and women. Maybe cutting his hair was a way for him to show the jury, as he sat there silently, day after day, while the prosecution presented its case, that, as his defense goes, he really didn’t mean for anything bad to happen. He is sorry for anyone he unwittingly hurt. He knows no one is above the law. Indeed, he has already begun to punish himself for his mistakes and to atone.

Will it work? We will have to wait and see.

It may seem a bit inconsequential, but prosecutors are going after statements Bankman-Fried made about his hair and cargo pants in the past to show that there was as lot of stagecraft with his image.

Bankman-Fried has previously said that he kept his hair unkempt and wore casual clothes because he was “busy and lazy.” Sassoon, the prosecutor, is trying to make the point that it was actually a carefully crafted image.

We are back and Bankman-Fried is being questioned about statements he made about his unkempt hair in the past, statements which he said he doesn’t recall. He is being shown an article from The New York Times.

Bankman-Fried said he doesn’t recall if he read the story.

Mr. Bankman-Fried, 31, charged with defrauding customers and investors in his FTX crypto exchange, is on the stand in one of the biggest white-collar cases to go to trial in the Manhattan courthouse since a crackdown on insider trading in the hedge fund industry roughly a decade ago. That investigation led to dozens of convictions, including that of Raj Rajaratnam, a onetime hedge fund billionaire. (Mr. Rajaratnam was released from federal prison in 2019 after serving just under eight years of an 11-year sentence.)

Mr. Bankman-Fried is facing questions from Danielle Sassoon, an assistant U.S. attorney in the Southern District of New York — an office with a well-earned reputation for being the main cops on the beat when it comes to policing Wall Street and financial crime.

Some of that comes simply from proximity — the U.S. attorney’s office in Manhattan and the federal courthouse are both just a few blocks from Wall Street. The Southern District has also long been a magnet for recruiting and attracting lawyers who are well versed in going after securities fraud and money laundering.

John P. Fishwick Jr., a former U.S. attorney for the Western District of Virginia, said the Southern District’s reputation as the premier office to go after financial crime was well deserved. It “has experienced financial prosecutors and agents who can root out sophisticated swindlers,” he said.

Before prosecutors took over questioning on Monday morning, he explained why he continued to give interviews and speak publicly even after the collapse of his cryptocurrency exchange, FTX. “I wanted to tell the world what I knew,” he said.

Mr. Bankman-Fried was arrested in December and charged with orchestrating a yearslong scheme to misappropriate as much as $10 billion from customers who had deposited their savings in FTX, funneling money to the hedge fund he founded, Alameda Research.

When he took the stand on Friday morning, the FTX founder showed little emotion as he defended his decisions in front of a packed courtroom. He began his testimony with a mea culpa, acknowledging that FTX’s collapse had hurt people throughout the crypto industry. All he had wanted to do, he said, was “build the best product on the market.”

Mr. Bankman-Fried walked the jury through his biography, from his upbringing in Palo Alto, Calif., to his undergraduate education at the Massachusetts Institute of Technology. In college, he said, he belonged to an unusual kind of fraternity that was “coed, nerdy and dry,” before graduating into a job at the Wall Street trading firm Jane Street.

At times, he cast himself as something of a novice. When he started trading cryptocurrencies with Alameda in 2017, he said, “I had absolutely no idea how it worked.”

His business empire grew faster than he had ever imagined, Mr. Bankman-Fried testified. He was soon working 22-hour days, he said, and receiving thousands of emails daily. He also started making political donations, he said, after concluding that “I could have a substantial impact on the world.”

Mr. Bankman-Fried suggested that the sheer volume of work caused him to ignore important parts of the business. Asked whether FTX had a risk management department, he said, “We sure should have, but no we did not.”

That exchange echoed a core claim of the defense: that Mr. Bankman-Fried was effectively building a plane in midair, and acting in “good faith” the whole time.

Mr. Bankman-Fried also reiterated several other claims that his lawyers have pressed throughout the trial. He denied illegally backdating documents, and said he used legitimate sources of funding to finance investments and real estate purchases.

He also blamed the problems at Alameda on Caroline Ellison, the firm’s chief executive and his former girlfriend, saying she had failed to properly manage risk. (Ms. Ellison has pleaded guilty and testified against Mr. Bankman-Fried.) He learned about an $8 billion hole in FTX’s accounts much later than prosecutors had asserted, he added.

At times during the testimony, Mr. Bankman-Fried seemed strikingly relaxed, smiling and making occasional wisecracks. He said he had passed on a possible stadium sponsorship with the Kansas City Royals because he didn’t want FTX “to be known as the Kansas City Royals of crypto exchanges.”

Asked why his hair was so unkempt throughout his tenure at FTX, he said, “I was kind of busy and lazy.”

When he responded to one question by saying he did not specifically recall making promises to his users that their funds were safe, she pulled up one of his Twitter posts.

“As always, our users’ funds and safety come first,” Mr. Bankman-Fried had written in the post, part of a series on the platform, now called X, that were shown in court.

The exchange underscored the enormous risk posed to Mr. Bankman-Fried — whose collapsed exchange wiped out billions in customer money when it failed last November — by his decision to take the stand in a trial that could put him in prison for decades.

Prosecutors will continue their cross-examination when the trial resumes on Tuesday morning. After that Mr. Bankman-Fried’s lawyers are expected to pose additional questions to him.

Mr. Bankman-Fried is accused of orchestrating a yearslong scheme to misappropriate as much as $10 billion from customers who had deposited their savings in FTX. They have accused him of funneling the money into venture capital investments, political contributions and extravagant real estate purchases.

Mr. Bankman-Fried, 31, is also accused of using the funds to prop up a crypto trading firm he founded, Alameda Research. Although he largely remained collected during the questioning by Ms. Sassoon, he became evasive as she asked him when he knew that Alameda — which was deeply enmeshed with FTX — would not be able to pay back money it had borrowed from FTX’s unwitting users.

Ms. Sassoon also needled Mr. Bankman-Fried at times.

“You think of yourself as a smart guy?” Sassoon asked in one question that invoked his time at the Massachusetts Institute of Technology.

Mr. Bankman-Fried replied, “In many ways, not in all ways.”

Here’s what to know:

• In earlier testimony, Mr. Bankman-Fried offered a mea culpa about the collapse of FTX and acknowledged making mistakes — but denied that he had committed fraud or stolen from his customers. The defense has sought to show that Mr. Bankman-Fried is not a criminal, but acted in “good faith” while attempting to manage an empire that grew far too quickly for him to properly manage.

• Even after FTX collapsed, Mr. Bankman-Fried continued to do interviews with TV anchors and obscure Twitter personalities, and invited reporters to visit him so he could continue defending his actions. Prosecutors have sought to use those words against him.

• Prosecutors offered a parade of witnesses — many of them high-ranking FTX executives — who blamed the firm’s collapse on Mr. Bankman-Fried.

• The collapse of FTX harmed three groups of victims: customers, investors and lenders. Here’s a look at those who lost money.

Four years later, prosecutors who have charged Mr. Bankman-Fried with sweeping fraud put that tweet up on a monitor at his criminal fraud trial in Manhattan. On the same day that the FTX founder sent it, one of the government’s witnesses testified, Mr. Bankman-Fried had directed the creation of a special backdoor that allowed Alameda to steal billions of dollars in FTX customer deposits.

The presentation to the jury was part of a pattern: Over and over during Mr. Bankman-Fried’s trial, prosecutors have used his own words against him.

Throughout his rise and fall, Mr. Bankman-Fried, 31, hardly ever stopped talking. As he built FTX into a $32 billion company, he texted with reporters and tweeted incessantly. After FTX collapsed last year, he defied his lawyers’ advice and embarked on a weekslong media tour, appearing on TV to defend his actions.

Those public statements are starting to backfire. At the trial, prosecutors have cited Mr. Bankman-Fried’s tweets, interviews, congressional testimony and off-the-cuff musings to argue that he repeatedly lied to the public. When one of his old allies, the FTX executive Gary Wang, took the stand, prosecutors pulled up a screenshot of a tweet that Mr. Bankman-Fried posted just days before FTX filed for bankruptcy.

“FTX is fine,” it said. “Assets are fine.”

“Was that accurate?” one of the prosecutors, Nicolas Roos, asked Mr. Wang.

“No,” Mr. Wang responded. “FTX was not fine, and assets were not fine.”

At another point, prosecutors played a clip from an interview that Mr. Bankman-Fried gave to the Bloomberg News columnist Matt Levine more than a year before FTX’s demise. Mr. Wang testified that Mr. Bankman-Fried had lied to Mr. Levine about the state of the exchange’s finances.

Some of the most potentially damaging excerpts came from interviews that Mr. Bankman-Fried gave after FTX filed for bankruptcy.

One prosecutor, Danielle Sassoon, showed the jury part of an interview that Mr. Bankman-Fried did with ABC’s “Good Morning America” after FTX imploded.

In the video, Mr. Bankman-Fried looks vaguely confused as he tries to answer an aggressive line of questions from the interviewer, George Stephanopoulos. When Mr. Stephanopoulos points to a document saying that FTX wasn’t allowed to use its customers’ funds for loans, Mr. Bankman-Fried slowly whispers to himself, “They can’t be loaned out.”

Ms. Sassoon also had a witness read aloud a Twitter direct-message conversation from November between Mr. Bankman-Fried and Kelsey Piper, a journalist who published the exchange in Vox.

Mr. Bankman-Fried later said that Ms. Piper was a friend and that he thought the conversation was off the record. Over dozens of messages, he appeared to dismiss the concept of ethics as a “dumb game we woke Westerners play where we say all the right shiboleths and so everyone likes us.”

At another point in the chat, Mr. Bankman-Fried used an expletive to dismiss government regulators as useless.

“They make everything worse,” he wrote.

Dwelling on it isn’t helpful, he said.

“It does affect you psychologically,” said Mr. Alam, 32. “My trust is completely gone. I don’t trust any of these apps, actually. I feel like they’re all Ponzi schemes.”

Mr. Alam is one of three kinds of victims Mr. Bankman-Fried has been accused of defrauding. The other two are venture capital investors and lenders.

Customers used FTX to invest their money in crypto. Venture capital firms such as Sequoia Capital and Paradigm provided nearly $2 billion in funding to build FTX, with many wiped out when the exchange filed for bankruptcy. FTX’s lenders, often other crypto exchanges, were also financially entangled — some were unable to fulfill their own customer withdrawals after the company imploded.

Mr. Bankman-Fried is accused of misusing $8 billion in customer deposits.

In the first three weeks of the trial, prosecutors called several victims to testify, including a Silicon Valley institutional investor and an executive from BlockFi, a lender to Alameda Research, FTX’s sister hedge fund. Prosecutors also called two customers who lost money: a London cocoa trader and a Canadian hotel magnate.

Judge Lewis A. Kaplan, who is presiding over the trial, prevented Mr. Bankman-Fried’s lawyer from questioning those witnesses about their own “gullibility and negligence” in investing in something as speculative as crypto.

The Commodity Futures Trading Commission has filed a civil suit seeking repayment for customers, but the agency has warned that even a court order demanding repayment “may not always result in the recovery of lost money because the wrongdoers may not have sufficient funds or assets.”

FTX and Alameda are working to settle debts with lenders and individuals through bankruptcy proceedings. Lawyers handling the bankruptcy said they had recovered $7 billion so far, less than half of what creditors say they are owed.

Customers are also trying to get their money back through class action lawsuits, which blame not only FTX officials but also celebrities and the venture capital firms that promoted the exchange.

“We thought if these big companies are investing in this exchange, I guess we’ll be safe too,” said Mr. Alam, who has not filed a suit. “But we lost everything; they’re still fine.”

Here are highlights of the testimony from several prosecution witnesses — including Mr. Bankman-Fried’s employee and on-again, off-again girlfriend, Caroline Ellison — who have been central to the case:

Adam Yedidia

The first prosecution witness was Adam Yedidia, a former FTX developer who was a close friend of Mr. Bankman-Fried’s and lived with him and other associates in the Bahamas.

Mr. Yedidia, who has not been charged with any crimes and testified under immunity, said Mr. Bankman-Fried had known that FTX and Alameda Research, a sister crypto trading firm, were on thin ice.

Mr. Yedidia described a conversation he had with Mr. Bankman-Fried at their paddle tennis court the summer before FTX collapsed, as the crypto market crashed and lenders to Alameda were asking for their money back. Mr. Yedidia said Mr. Bankman-Fried had told him that FTX “was bulletproof last year, but we’re not bulletproof this year” and that it would take six months to three years to make the company “bulletproof again.”

Caroline Ellison

Ms. Ellison, who ran Alameda and was Mr. Bankman-Fried’s former girlfriend, was the government’s star witness. She detailed the close relationship between Alameda and FTX, including several instances when, she said, Mr. Bankman-Fried directed or greenlighted the use of FTX’s customer deposits.

Ms. Ellison, who has pleaded guilty to fraud charges and is cooperating with prosecutors, said Mr. Bankman-Fried had been eager to buy back FTX shares from Binance, a rival crypto exchange. She was apprehensive about the move, she said, because she knew that would mean borrowing $1 billion in FTX customer funds for the transaction.

“That’s OK, I think this is really important, we have to get it done,” Mr. Bankman-Fried told Ms. Ellison, according to her testimony.

Ms. Ellison also offered insight into Mr. Bankman-Fried’s mind-set, detailing their relationship and his somewhat unconventional view that rules about not lying and not stealing were of lesser importance than actions that he saw as serving a greater good.

Gary Wang

Mr. Wang, an FTX co-founder who has pleaded guilty in the case and agreed to cooperate with prosecutors, told the jury that Mr. Bankman-Fried had directed him to include features on the exchange that gave Alameda an advantage on the platform. “In the end, it was Sam’s decision,” he testified.

The soft-spoken coder spent much of his time on the stand explaining the intricacies of FTX’s computer code, which supported prosecutors’ point that Alameda was intentionally given special privileges on the platform so it could use FTX customer deposits as if they were a piggy bank.

Mr. Wang met Mr. Bankman-Fried in high school math camp, and they were classmates at the Massachusetts Institute of Technology before founding FTX together in 2019.

Nishad Singh

Mr. Singh, a former FTX executive who has also pleaded guilty, detailed Mr. Bankman-Fried’s lavish spending, including big real estate purchases and political donations. That spending, he said, was bankrolled by FTX customer deposits.

Mr. Singh said he had given other associates access to his bank accounts to make political donations under his name, including Mr. Bankman-Fried’s younger brother, Gabe, who ran the nonprofit group Guarding Against Pandemics. At one point, when a credit wire wasn’t going through, Gabe Bankman-Fried sent one of his assistants to the Bahamas “with a bunch of checks from my bank account,” Mr. Singh testified.

Prosecutors also showed an email exchange between Mr. Singh and Mr. Bankman-Fried’s mother, Barbara Fried, who was receiving $1 million from FTX for her nonprofit Mind the Gap. Ms. Fried, a Stanford law professor, suggested that Mr. Singh make the donation under his name “because we don’t want to create the impression that funding MTG is a family affair, as opposed to a collective effort by many people (including some mystery guy Nishad Singh :)).”

Can Sun

Mr. Sun, a former top FTX lawyer, testified that Mr. Bankman-Fried had pushed him to find a legal justification for the exchange’s repeated misuse of billions in customer money — even after Mr. Sun told his boss there was none.

At Mr. Bankman-Fried’s urging, Mr. Sun said, he ran through a few theoretical options to justify the borrowing and spending of FTX customer money. But Mr. Sun, who testified after securing an agreement that prosecutors would not pursue charges against him, said he had once again told Mr. Bankman-Fried that none of those options were supported “by the facts.” Mr. Bankman-Fried responded by saying “something like, ‘Got it,’” Mr. Sun testified.

Prosecutors then played a clip from an interview that Mr. Bankman-Fried gave ABC’s “Good Morning America” days before FTX filed for bankruptcy in November. In that interview, Mr. Bankman-Fried offered up one of the theoretical options that Mr. Sun had provided him as an explanation for what happened to FTX’s customer money.