Fraudster Bernard Madoff's former accountant Paul Konigsberg pleaded guilty to helping the convicted financier with his Ponzi scheme by falsifying records.
"I'm here today to take responsibility for what I did that was wrong," the former senior tax partner at Konigsberg Wolf & Co said before US District Judge Laura Taylor Swain in New York.
He pleaded guilty to two counts of falsifying records and one count of conspiracy and agreed to forfeit $4.4m. He is likely to get a maximum prison term of 30 years.
However, he noted that he was not aware of the Ponzi scheme.
"It is important for me, your honor, to let you know that I was not aware of Madoff's horrific and evil Ponzi scheme," he said.
Meanwhile, prosecutors said even if Konigsberg did not intend to help defraud Madoff investors, he knowingly used fraudulently backdated trades provided by Madoff's firm to prepare tax returns for some clients' investment accounts.
He handled accounting work for Madoff's clients, representing more than 300 investment accounts. In addition to the fees from the clients, he received monthly payments from Madoff's firm for the 'help' rendered.
Konigsberg, who initially pleaded not guilty, was the 15th person to be convicted at trial or to plead guilty in connection with the fraud, which is estimated to have cost customers more than $17bn (£10bn, €12.5bn) in principal.
In March, five former Madoff aides were found guilty of securities fraud and conspiracy to defraud clients.
The five aides are computer programmers Jerome O'Hara and George Perez, back-office director Daniel Bonventre, and portfolio managers Annette Bongiorno and Joann Crupi. All are seeking to have their convictions dismissed.
Madoff pleaded guilty in 2009 and was sentenced to 150 years in prison for controlling the biggest Ponzi scheme in history. His brother Peter Madoff pleaded guilty in 2012 to his part in the fraud and was sentenced to 10 years in jail.