Fresh details about the alleged billion-dollar Ponzi scheme run by Bernard L. Madoff have come to light as the fallen financier prepares himself for a possible guilty plea in federal court later this week.

Annette Bongiorno, a longtime aide to the New York investment manager, allegedly instructed two assistants to create fake trading tickets using research of daily share prices for blue-chip stocks, The Wall Street Journal reported today.

The "tickets" would show purported trades that Madoff had made, which were in line with the annual profit reports his firm issued to investors. The two assistants were interviewed by federal authorities last month, according to the report.

Such fact-gathering doesn't mean that prosecutors will determine there was any criminal liability. That said, even if prosecutors don't find any individuals had an "intent to defraud" investors, they can still bring fraud charges based on the argument that an individual was "willfully blind," meaning that they were "aware of the high probability that there's a fraud going on but consciously and deliberately avoided confirming that it was in fact a fraud," says David Siegal of Haynes and Boone, formerly a Southern District AUSA.

Last month, Bloomberg reported that the 60-year-old Bongiorno recruited potential Madoff investors from her Howard Beach neighborhood in Queens, N.Y. Another Madoff employee, 33-year-old chief financial officer Frank DiPascali, has also been the subject of the ongoing federal probe.

No other Madoff employees have been charged in connection with the case, but banking and law-enforcement experts are dubious of Madoff's claims that he acted alone (as they are with the $50 billion figure attached to the Ponzi scheme).