Irwin Lipkin, one of Bernard Madoff's longest-serving employees, was sentenced to six months in prison Wednesday for falsifying records that helped the imprisoned fraudster carry out his multibillion-dollar Ponzi scheme.

The sentencing before U.S. District Judge Laura Taylor Swain in Manhattan marked the end of the criminal prosecutions stemming from the fraud, more than six years after Madoff's arrest sent shockwaves through Wall Street.

Lipkin, 77, was the Madoff firm's controller from 1964 to 1998. He was the last of 15 defendants who either pleaded guilty or were convicted at trial to be sentenced.

Madoff, also 77, is serving a 150-year prison term after pleading guilty in 2009 to masterminding the scheme, estimated to have cost investors $17 billion in principal.

Lipkin pleaded guilty in 2012 but, like other defendants, said he was unaware Madoff was running a Ponzi scheme.

"Smarter people than myself were taken in by him," Lipkin, who was confined to a wheelchair, told Swain on Wednesday.

But Assistant U.S. Attorney David Abramowicz said Lipkin, and others, helped Madoff perpetuate his scheme through their crimes, even if they didn't know the entire truth.

"The lesson we've seen in this parade of guilty defendants is: Bernard Madoff didn't do this alone," he told Swain. "He needed help, and he found it in people like Irwin Lipkin."

Swain said she would have imposed a far longer sentence if not for Lipkin's age and poor health.

In addition to six months in prison, Swain sentenced Lipkin to 1-1/2 years of home confinement. She also said the Federal Bureau of Prisons could convert his prison term to home confinement if necessary for his health.

Lipkin was accused of falsifying records to fool government regulators and help Madoff mislead tax auditors about his income.

He also arranged for fake trades in his investment accounts for tax reasons and kept himself and his wife on the firm's payroll even when they were not employed there, prosecutors said.

Unlike several other defendants who pleaded guilty, Lipkin did not cooperate with prosecutors.

Five Madoff employees -- back-office director Daniel Bonventre, portfolio managers Annette Bongiorno and JoAnn Crupi and computer programmers Jerome O'Hara and George Perez -- were found guilty by a jury last year on all counts.

They were sentenced to between 2-1/2 and 10 years in prison and are appealing their convictions.

The case is U.S. v. O'Hara et al, U.S. District Court, Southern District of New York, No. 10-cr-00228.

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