NEW YORK (CBSNewYork/AP) — A judge sentenced the last defendant in the Bernard Madoff Ponzi scheme case on Wednesday to six months in prison.

The sentencing for Irwin Lipkin marked the end of a prosecution that lasted more than six years and dispelled claims by Madoff that he acted alone in pulling off his epic Ponzi scheme that bilked investors of billions.

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Lipkin, 77, had pleaded guilty in 2012 to helping conceal the fraud from regulators by falsifying records as comptroller of the firm. He is among a total of 15 defendants charged in the case, including Madoff, who either pleaded guilty or were convicted at trial.

The defense had argued that Lipkin shouldn’t go to prison because of his failing health and because he didn’t know the full extent of Madoff’s scheme. The government countered by accusing him of trying to minimize his role, and told the judge that a prison term was appropriate.

Madoff “didn’t do this alone,” prosecutor David Abramowicz said in federal court in Manhattan. “He didn’t do it alone because he couldn’t do it alone. He needed the help of people like Mr. Lipkin.”

A frail-looking Lipkin, who was hired as one of Madoff’s first employees in the 1960s, had admitted in his guilty plea that he knowingly certified false documents. But he also told U.S. District Judge Laura Taylor Swain that during the decades he worked for Madoff, he believed the operation “was absolutely on the up and up.”

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Still, he added: “I would like to apologize to the court and to everybody else who may have been hurt by the things that I’ve done.”

Madoff revealed his fraud in December 2008 amid a collapsing economy, acknowledging that account statements showing that clients held nearly $68 billion were a sham. The roughly $17.5 billion in principal invested by retirees, charities and other clients over decades was mostly gone — paid out as fake profits or raided by Madoff’s family and cronies.

Madoff pleaded guilty to fraud charges a few months later and was sentenced to a 150-year prison term in Butner, North Carolina.

Sentences for the remaining 14 defendants have ranged from 10 years for Madoff’s brother, Peter, and another top executive at the firm to no prison time for cooperators. One defendant died before he could be sentenced.

The judge also sentenced Lipkin to 18 months of house arrest after he serves his prison term.

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