Bernie Madoff's longtime accountant, David Friehling, pleaded guilty Tuesday to abetting one of the most devastating Ponzi schemes in history, which brought down thousands of victims and more than $21 billion in lost funds. Friehling, who verified Madoff's accounts for nearly 20 years, admitted that he never legitimately audited the brokerage firm and acknowledged his conflict of interest as an independent auditor because of his own investments in Madoff's operation. Friehling still maintained, as he has since the day of his arrest, that he was not aware of the Ponzi scheme. Friehling is cooperating with federal investigators in hopes of a more favorable sentence. His guilty plea to nine criminal charges could land him in jail for up to 114 years. Madoff is serving a 150-year sentence in North Carolina.