Bernard Madoff has recanted his claim that he operated his epic Ponzi scheme alone, conceding in the years since his arrest that others knew what he was up to and contributed to the scheme.

But he has never fingered any of the members of his small office staff, some of whom worked with him for decades churning out the paperwork and performing the routine bookkeeping duties that helped perpetuate the multi-billion-dollar fraud.

On Monday a federal jury in New York began deliberations to decide whether five of those staff members were duped by Madoff, as they claim, or were complicit in their boss’s crimes.

The case is the first criminal trial to spring directly from Madoff’s scheme, which investigators  say operated for more than two decades and bilked investors of an estimated $17 billion.

The five defendants are back-office manager Daniel Bonventre; portfolio managers Annette  Bongiorno and Joann Crupi; and computer programmers Jerome O'Hara and George Perez.

According to an indictment handed down in July, the five employees assisted Madoff by, among other activities, creating false documents that were distributed as statements to Madoff’s investors. The statements used complicated Wall Street jargon to suggest Madoff was employing sophisticated techniques to generate the handsome profits he used as his calling card, prosecutors allege.

Since Madoff’s arrest, investigators have revealed that he made virtually no trades at all and fabricated all his records. He used the money generated from new investors to cover profits paid to older investors – a classic Ponzi scheme.

Madoff turned himself in in late 2008 as the fraud was unraveling, undone by the onset of the financial crisis. The scheme collapsed as many of his clients sought redemptions and Madoff realized he couldn’t possibly repay all those who wanted their money back.

Madoff pleaded guilty to numerous crimes and is serving a 150-year sentence in federal prison.

The trial of the five Madoff staffers -- their cases were tried simultaneously -- has lasted over five months and closing arguments alone lasted more than 25 hours and stretched over two weeks. More than 40 witnesses were called to testify and some 1,600 exhibits introduced.

All five claim they came to work each day at Madoff’s office in midtown Manhattan and performed their duties without ever realizing they were assisting in one of the largest financial frauds in history.

All five offered slightly different versions of the same defense -- Madoff was the only person in the office who knew the whole story. Everyone else performed their specific functions without realizing they were contributing to a massive financial fraud.

But Madoff’s right hand man, Frank DiPascali Jr., the long-time office manager of Bernard L. Madoff  Securities, cast doubt on that defense.

DiPascali pleaded guilty in 2009 to multiple counts of fraud and was a key witness for the prosecution during the trial. In effect, he told the jurors that everyone in the office knew Madoff was running a scam.

John Coffee, a Columbia University law professor and expert in white-collar crime, said much of the case boils down to whether the jury believed DiPascali or the defendants.

“Do you believe the principal witness, one of Madoff’s key henchman, or do you believe the testimony of defendants who claimed they never saw the light?” Coffee asked.

In a risky strategy that put them in the direct crosshairs of prosecutors, two of the defendants –  Bonventre and Bongiorno – took the stand in their own defense during the trial. The other three declined the opportunity to defend themselves in testimony.

Bonventre, Bongiorno and Crupi were all long-time Madoff employees, working on the 17th  floor of mid-town Manhattan’s Lipstick Building, one floor below Madoff’s legitimate market making business, which was run primarily by his brother, Peter, and his two sons, Andrew and Mark.

Peter Madoff was sentenced to 10 years in prison in December after pleading guilty to participating in the fraud. Andrew and Mark Madoff were never charged in the scheme. Mark Madoff committed suicide in December 2010.

The other two defendants, O’Hara and Perez, were computer programmers. In court documents their lawyers have said the two merely carried out orders -- programming data -- given to them by employees who worked closely with Madoff.

Including Peter Madoff and DiPascali, a total of nine former employees have pleaded guilty in the scam.

Follow Dunstan Prial on Twitter @DunstanPrial