Since Sam Bankman-Fried was convicted of fraud last year, he has hired a new lawyer known for his courtroom showmanship. A group of sympathetic law professors have pushed for a reevaluation of his actions. And his parents have turned to former employees of FTX, the cryptocurrency exchange he founded, for help.

From a federal detention center in Brooklyn, Bankman-Fried, 31, has continued to fight her case behind the scenes as she seeks a lenient sentence and prepares to appeal her conviction. On Tuesday, his attorneys filed a legal memorandum in U.S. District Court in Manhattan, arguing that he should receive a prison sentence of between five and a quarter to six and a half years.

Bankman-Fried is “deeply sorry” for “the pain he caused over the past two years,” the memo said. “His only goal after the FTX collapse was to restore the integrity of customers.”

The filing was a crucial step ahead of Mr. Bankman-Fried’s sentencing on March 28, when the federal judge overseeing his case, Lewis A. Kaplan, will decide how long to jail the one-time billionaire on charges that carry a maximum sentence of 110 years. But it was just one part of a far-reaching strategy orchestrated by Bankman-Fried’s family and friends to reverse his conviction and engineer a public reassessment of his leadership at FTX.

Since last year’s trial, Bankman-Fried has hired Marc Mukasey, who once represented former President Donald J. Trump, to oversee her sentencing, as well as an independent attorney from the law firm Shapiro Arato Bach to handle the appeal. His parents, Stanford University law professors Joe Bankman and Barbara Fried, have also been involved in the defense, helping to train people to write letters endorsing their son’s character that were included in the sentencing memorandum. .

In an interview, Natalie Tien, Bankman-Fried’s former assistant at FTX, said she had written a letter for the memo after exchanging emails with Bankman and Fried.

“I don’t hold a grudge against him and I feel bad for his parents,” Ms. Tien said.

A spokesman for Bankman-Fried declined to comment. Representatives for Bankman and Fried did not respond to requests for comment.

Federal prosecutors are about to outline their own sentencing recommendation in a filing due March 15. But according to Bankman-Fried’s memo, a probation officer already recommended a sentence of 100 years, a punishment his attorneys called “barbaric.”

Even if Judge Kaplan decides not to impose the maximum sentence, Bankman-Fried could face decades behind bars.

The judge “could still impose a very serious sentence given how young Mr. Bankman-Fried is, say, a sentence of 30 or 35 years,” said Miriam Baer, ​​vice dean at Brooklyn Law School.

A spokesman for Damian Williams, U.S. Attorney for the Southern District of New York, declined to comment.

Before FTX collapsed in November 2022, Bankman-Fried was one of the most prominent figures in the renegade crypto industry, a highly celebrated billionaire whose face appeared on billboards and magazine covers.

In October, a federal jury convicted him of stealing $8 billion from FTX clients to finance political contributions, investments in other companies and lavish real estate purchases.

Bankman-Fried has maintained his innocence and vowed to appeal. This month, he replaced his trial attorneys, Mark Cohen and Christian Everdell, with Mr. Mukasey, who represents another fallen crypto tycoon. in a separate case and has a reputation for making forceful presentations in court.

Last year, Mukasey scored a victory in his defense of Trevor Milton, the founder of electric truck maker Nikola, who was convicted in 2022 of defrauding investors. A federal judge sentenced Milton in December to four years in prison, far less than the 11 years prosecutors had requested.

Working alongside Mr. Mukasey is an appeals lawyer and former prosecutor, Alexandra Shapiro, partner of Shapiro Arato Bach. He is expected to present Mr. Bankman-Fried’s appeal after the sentencing.

Bankman and Fried have also played a role behind the scenes. Last month, Tien said, he received a text message from one of Bankman-Fried’s supporters, asking if he would help with the memo. She then received a follow-up email from the FTX founder’s parents explaining her sentencing process and urging her to write “from the heart” about her son.

They were “like testing the water,” Tien said in an interview. “I pretty much said ‘yes’ right away.”

Tien was one of 29 people who wrote letters for the memo, including Bankman-Fried’s parents, her younger brother and several former colleagues. She called him kind and empathetic and said he had “never acted out of greed or self-interest.”

In the filing, Mukasey cited the letters to describe Bankman-Fried as a selfless, hard-working billionaire who avoided the pitfalls of fame and wealth. He also argued that some oddities in the tycoon’s behavior could be explained by “neurodiversity.”

Bankman-Fried has “outward characteristics typical of neurodiversity, such as inconsistent eye contact,” the memo said. “You may be perceived as abrupt, dismissive, evasive, distant or indifferent.”

Outside of the formal court process, law professors who know Bankman-Fried’s parents have also pressed their case.

In January, two close family friends, Yale Law professor Ian Ayres and Stanford Law professor John Donohue, wrote an essay for the Project Syndicate websitearguing that “from the beginning” FTX had enough assets to satisfy its customers, a point Mukasey echoed in the memo.

“Whatever else can be said about Bankman-Fried, he was a brilliant businessman,” Ayres and Donohue wrote.

Another law professor, Jonathan Lipson of Temple University, said in an interview that he was working with David Skeel of the University of Pennsylvania Law School on an academic paper that criticized Sullivan & Cromwell, the law firm he oversaw. the bankruptcy of FTX.

In September, Mr. Lipson co-wrote a brief in the bankruptcy case arguing for the appointment of an independent examiner to review Sullivan & Cromwell’s actions, including its close collaboration with federal prosecutors. He said he had spoken to Bankman-Fried and her mother last year after another Stanford law professor reached out to the case and offered to put them in touch.

In their article, Lipson and Skeel argue that Sullivan & Cromwell “may have distorted the criminal justice process” by giving prosecutors broad access to FTX resources and data, according to an unpublished draft shared with The New York Times.

A Sullivan & Cromwell spokesman declined to comment. In court documents, prosecutors described the information sharing as “routine practices of companies cooperating in an investigation.”

Bankman-Fried faces many difficulties. Criminal convictions are rarely overturned on appeal.

Since last summer, he has been housed at the Brooklyn Metropolitan Detention Center, where he has spent much of his time working on the case, said a person with knowledge of the matter. Bankman-Fried also shared advice on the cryptocurrency market with the guards, the person said, recommending investments in the digital currency Solana.

This month, Bankman-Fried left the detention center for her first public court appearance since the trial, a hearing to authorize her new legal representation. In a Manhattan courtroom, he appeared clean-shaven and wearing a baggy brown prison uniform. Sometimes he would turn and smile at the journalists sitting in the gallery.

J. Eduardo Moreno contributed with reports.