Sam Bankman-Fried, the former billionaire crypto boss who was convicted of fraud and money laundering last year, will return to court in New York on Thursday to be sentenced for his crimes.

It is certain the 32-year-old will be going to jail; what is not known is how long for.

The moment has revived debate about the extent of his crimes – and what punishment might fit.

His legal team have called for leniency, but prosecutors are seeking 40 to 50 years in prison.

They say such a sentence is warranted for someone who lied to investors and banks, and stole billions in deposits from customers of his now-bankrupt crypto exchange, FTX.

His defence team has proposed five to 6.5 years, accusing the government of adopting “a medieval view of punishment” by insisting on a lengthy term behind bars for a non-violent, first-time criminal.

The question has generated hundreds of pages of letters from former FTX customers, family, friends of his parents – even complete strangers – trying to sway Judge Lewis Kaplan, the federal justice who will decide his fate.

“He has shown no remorse so why would any judge show any mercy?” said Sunil Kavuri, a British investor who had more than $2m worth of holdings on the exchange when it collapsed, and one of the people mobilising former customers to share their experience with the court.

Sunil Kavuri faces a long and uncertain wait to retrieve any of his investment

FTX’s collapse in 2022 was a stunning fall for Bankman-Fried, who had become a billionaire and business celebrity promoting the firm, a platform people could use to deposit and trade crypto.

It attracted millions of customers, before rumours of financial trouble sparked a run on deposits.

In November 2023, a US jury found Bankman-Fried had stolen billions in customer money from the exchange ahead of the collapse to buy property, make political donations and use for other investments.

Many of those customers now appear poised to recover significant sums, under a plan being developed in the separate bankruptcy case.

Under that proposal, former customers could receive money based on what their holdings were worth at the time the exchange collapsed.

In court filings, the defence for Bankman-Fried, who is expected to appeal his conviction, has argued that such recovery warrants a lighter sentence.