Madoff mysteries remain as he nears guilty plea

It may be impossible to calculate that figure because the scheme ran for so long and involved so many investors, experts say.

"There is likely a lack of records going back from the inception of the scheme," said George Jackson, an attorney in the Chicago office of law firm Bryan Cave and a former federal prosecutor.

NEW ESTIMATE

U.S. prosecutors have given a new estimate of the size of the worldwide scheme -- $64.8 billion -- up from the $50 billion fraud they said Madoff confessed to in December.

The government said in court papers that the $64.8 billion was based on the purported amount held collectively by Madoff investors as of November 30, 2008, based on about 4,800 client accounts.

In reality, prosecutors said, the Madoff firm "held only a small fraction of that balance."

A trustee overseeing the liquidation of Madoff's brokerage said last month he had recovered less than $1 billion for customers -- a fraction of their overall deposits. Prosecutors are separately demanding fines, forfeiture and restitution from Madoff, but it is unclear how much money he has.

Madoff is expected to plead guilty to all 11 counts filed against him when he appears in court on Thursday, his lawyer told a judge on Tuesday.

Prosecutors say there is no plea agreement with Madoff -- a type of deal in which defendants agree to enter a guilty plea and cooperate with the government in exchange for the possibility of more lenient treatment at sentencing.

His charges could bring 150 years in prison under sentencing guidelines.

Madoff has been under house arrest at his Manhattan penthouse apartment, but prosecutors may seek to jail him until his sentencing in several months' time.

Former prosecutor Steskal said it is unclear why Madoff appears set to plead guilty without a plea deal. He said prosecutors may have refused to offer one, but if that were the case then Madoff could have contested the charges.

"It's hard to know what is motivating him," Steskal said. "It may be as simple as he simply wants it over with."

The case is USA v Madoff 09-213 in U.S. District Court for the Southern District of New York (Manhattan)

(Editing by Brian Moss and Andre Grenon)