NEW YORK: Wall Street swindler Bernard Madoff faces his moment of truth Monday when a federal judge here pronounces a sentence that could be as much as 150 years in prison, though experts predict he will get much less.

More than six months after his fall from the height of the financial world, when his massive Ponzi scheme was uncovered, the 71-year-old former Nasdaq stock market chairman will face US District Judge Denny Chin and once again some of his victims.

Madoff faces up to 150 years in prison, but his lawyer has cited the disgraced mogul's advanced age in pushing for a 12-year sentence, while most experts anticipate at least 20 years in jail under harsh conditions.

In a document sent to Chin Friday, federal prosecutors rejected the lawyer's request and said that given "the scope, duration and nature of the crimes," Madoff should receive a 150-year sentence to "assure that Madoff will remain in prison for life." Chin also ordered that Madoff forfeit over 170 billion dollars in illegally obtained assets, following a request from the prosecutors.

In an accompanying order, a district court in New York also stipulated that wife Ruth Madoff be stripped of 85 million dollars in assets, leaving her with just 2.5 million dollars in cash.

"Madoff will get no less than a 20-year sentence and probably more than that," former federal prosecutor William Devaney told AFP.

Under US federal criminal law, a convict must serve at least 85 percent of their sentence and demonstrate good conduct during that time, which for Madoff translate to a minimum of 17 years in prison. At the end of that period, he would be 88 years old.

Devaney said his estimate was based on recent billion-dollar frauds, where the main perpetrator has received the equivalent of a life sentence.

The financier, who has pleaded guilty to bilking billions of investors in one of the biggest, most complex financial scams in Wall Street's history, could appeal, "but it would be very difficult for him to get his sentence overturned on appeal," Devaney said.

The Court of Appeals, he said, would make a ruling within a year on the case.

Due to the amount of the fraud, however, Madoff "would have no basis for an appeal," said Bradley Simon, a former federal prosecutor turned white collar defence attorney. He predicted that the Court of Appeals would likely "summarily dismiss any such appeal." He also estimated the sentence would be "20 years or more," adding: "that is pretty much like a life sentence for someone who is 71." According to Simon, the sentence will be "severe" but will also be reasonable so that it "won't be perceived as pandering to the angry crowd mob," referring to victims of the swindler and the general public.

Another lingering issue in the case is returning the swindled funds. Of the estimated 65 billion dollars of the fraud, prosecutors say about 13 billion dollars were handed to Madoff and only one billion dollars have been recovered from the liquidation of his assets. The financier himself has talked about losing some 50 billion dollars, which is believed to be the amount that would have been paid out had the funds been properly invested.

The sums were shockingly large -- bigger than the gross domestic product of countries such as Luxembourg, and more than the external debt of several poor African nations.

Of the billions of dollars that passed through his hands during his three-decade scam, Madoff has said he never invested one cent in the market. Instead, he stashed the funds in a Chase Manhattan bank account.

The funds were then used to pay out "dividends" to investors in his pyramid scheme.

With Madoff, who has been in jail since March after admitting guilt in the scheme, almost certainly set to remain in prison for the rest of his life, the condition of his detention has garnered significant interest.

But that is a decision that does not necessarily rest within the power of the federal judge, who can only make recommendations to the Bureau of Prisons. Given the length of the sentence, Devaney said Madoff likely would not qualify for a prison camp.

"He will be with people who have committed other type of offenses, more violent, and that sort of thing," Simon said.

Madoff has already obtained one small concession from Chin: that he show up in civilian clothing rather than a prison uniform at Monday's 10:00 am (1400 GMT) hearing in the southern Manhattan court.