Money to Be Returned to Madoff Investors Tops $5 Billion

CNBC has confirmed Madoff has made repeated offers of help since then, from the federal prison in Butner, NC, where he is serving a 150-year sentence. But Picard said Madoff has never been much help, even when he and Sheehan went to visit Madoff on two separate occasions.

"In my view, he has not been helpful. The interviews of him were, really, to confirm the information we found because those interviews took place shortly before some of our litigations began and we put this case together the litigation teams and really, from a blank slate," Picard said.

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"There's always the suggestion that there's more that he could help us with," Sheehan said. "But when we pressed his counsel to give us an example of that before we start getting on an airplane and fly down to see him, we never get anything that's worthwhile. So, we have not taken him up on those offers."

"I think he thinks that he's still in control of the situation, so that if you're going to come and interview him he could fix the ground rules. And that's not the situation," Picard said.

Picard and Sheehan said they no longer believe Madoff or members of his family have money secretly stashed away.

"My sense of it is that we found everything that there is to be had from Mr. Madoff and his family," Sheehan said.

(Read More: Madoff's Younger Brother Sentenced to 10 Years.)

—By CNBC's Scott Cohn; Follow him on Twitter: @ScottCohnCNBC