A Rockland accountant accused of helping Bernie Madoff conceal his multibillion-dollar Ponzi scheme pleaded guilty Tuesday at U.S. District Court in Manhattan.

David Friehling, of New City, pleaded guilty to securities fraud and other charges. Prosecutors say Friehling, who acted as Madoff's sole auditor from 1991 to 2008, did not conduct proper audits and thus aided Madoff in faking his books and stealing from investors.

Friehling says he was not aware of the Ponzi scheme at the time. He apologized to Madoff's victims in court.

Friehling will be sentenced in February. He faces up to 114 years in prison, but could get a lighter sentence if he cooperates with investigators.

AP wire reports contributed to this article.