Bernard Madoff was apparently convinced that it never even occurred to Securities and Exchange Commission staff he was running a Ponzi scheme, despite the agency's numerous probes of his business.

A document released Friday details a prison interview conducted on June 17 by the SEC inspector general in which Madoff says he had the impression that "it never entered the SEC's mind that it was a Ponzi scheme."

The disgraced financier confided that he didn't bring an attorney with him when he testified in an inquiry by the SEC's enforcement division because he believed he didn't need one - and he was trying to fool the government investigators into thinking he had nothing to hide.

As the SEC inspectors carried out probe after probe of his business, Madoff said in the interview he was "worried every time" that he'd be caught. "It was a nightmare for me," he said. "I wish they caught me six years ago, eight years ago."