Bernie Madoff, who bilked investors out of billions of dollars, will be sentenced Monday but legal experts say the fallout from the 71-year-old's giant Ponzi scheme is far from over.

Madoff is facing a maximum sentence of 150 years and is likely to never again see the outside of a federal prison.

Until earlier this week, only Madoff and his accountant, David Friehling, had been charged in connection to the scheme.

Then, on Monday, federal regulators charged a New York brokerage firm and a California investment adviser with securities fraud. The accused are said to have helped Madoff funnel billions of dollars.

Still, observers are wondering if Madoff's two sons, Mark and Andrew Madoff, will be charged, noting they worked closely with their father.

"The problem the government faces is linking them to the fraud," Peter Henning, a Wayne State University law professor who specializes in white collar crime law, told CTV.ca in a recent interview.

"Bernie took the bullet, he said 'I worked alone' and that they had nothing to do with this."

Henning said prosecutors can't just operate on speculation.

"Just having a suspicion is one thing and maybe they were suspicious but at this point there hasn't been any evidence that they were involved in his fraud," he said.

And what about Madoff's closest associate, his wife Ruth? Did she really have no idea what was going on?

"They're going to need someone who worked inside the investment advisory business who's going to be able to point the finger at her and say this was her involvement and put together essentially a circumstantial case," Henning said.

"Bernie is saying I did it all by myself so that oddly enough gives his wife and his sons a defence."

Henning said he expects Madoff's brother, Peter, will likely be targeted by prosecutors.

"He was a compliance officer (at Madoff's company)," Henning said.

"He has certain obligations to certify that the firm was being operated properly."

He said prosecutors want to make sure they have all their bases covered before going ahead with charges.

"In a lot of ways it's a very simple case -- he lied to everybody -- but going back and finding the involvement of others I think is no doubt what's taking time and the government wants to make sure they have a good case," Henning said.

Madoff's scheme wiped out almost $65 billion in investments when it collapsed.

Thousands of investors, ranging from Hollywood stars to ordinary people, lost money because of the scam.

Large hedge funds, banks and charities also lost money that was invested with Madoff's firm.