Did Madoff Act Alone? Prosecutors Say No

Bernard Madoff is expected to plead guilty tomorrow to orchestrating one of the biggest frauds in U.S. history - cheating investors out of billions of dollars over three decades.

Madoff insists he did it all by himself. But based on the sheer scope of the crime, prosecutors believe he must have had help, reports CBS News chief investigative correspondent Armen Keteyian.

People familiar with the case tell CBS News that federal investigators are "ripping apart" 20 years of fraud inside Madoff's firm. They're moving beyond Madoff himself and looking at sons Andrew and Mark, who directed trading activities, and brother Peter, the company's chief compliance officer. None of them have been charged with any wrongdoing.

"This is a case where they're going to leave no stone unturned," said Sean O'Shea, a former federal prosecutor. "They're going to get to the bottom of it. And everyone who has criminal culpability will be charged."

Also under the microscope: Madoff's wife of 49 years, Ruth, who has not been charged in the case. In court papers, she claims nearly $70 million in assets separate from her husband's fortune, including a $7 million New York apartment, $45 million in bonds, and $17 million in cash. She's also listed as the owner of a $9 million Palm Beach mansion.

Investigators are said to be interested in the $10 million she withdrew from a brokerage account just one day before her husband was arrested last December. She took out another $5.5 million two weeks earlier.

Asked if he believes the federal government is looking into Ruth Madoff's actions, O'Shea replied, "It would be hard to believe that they're not."

A source with knowledge of the investigation told CBS News that another subject of the probe is Madoff's chief financial officer, Frank DiPascali, the day-to-day contact for many investors.

Investor Dr. Murray Morrison says his last conversation with DiPascali, just weeks before Madoff's arrest, caught him by surprise.

"He told us that Bernie Madoff had said they probably shouldn't put anything in e-mails," Morrison said.

So now as Madoff prepares for what may be his last night of comfort in his posh penthouse apartment, the government is digging around to determine just how many could follow his path to prison.