“There’s no question we made money in these transactions. However, all our dealings were through arm’s-length transactions with experienced counterparties who had opposing views based on all available information at the time. We were straightforward in our dislike of these securities, but the vast majority of people in the market thought we were dead wrong and openly and aggressively purchased the securities we were selling.”

Still, the details unearthed by the S.E.C. in its investigation show a deep involvement by Mr. Paulson in the creation of the investment, known as Abacus 2007-AC1. For example, he approached Goldman about constructing and marketing the debt security.

After analyzing risky mortgages made on homes in Arizona, California, Florida and Nevada, where the housing markets had overheated, Mr. Paulson went to Goldman to talk about how he could bet against those loans. He focused his analysis on adjustable-rate loans taken out by borrowers with relatively low credit scores and turned up more than 100 loan pools that he considered vulnerable, the S.E.C. said.

Mr. Paulson then asked Goldman to put together a portfolio of these pools, or others like them that he could wager against. He paid $15 million to Goldman for creating and marketing the Abacus deal, the complaint says.

Image The investor John Paulson became a Wall Street celebrity. Credit... Rick Maiman/Bloomberg News

One of a small cohort of money managers who saw the mortgage market in late 2006 as a bubble waiting to burst, Mr. Paulson capitalized on the opacity of mortgage-related securities that Wall Street cobbled together and sold to its clients. These instruments contained thousands of mortgage loans that few investors bothered to analyze.

Instead, the buyers relied on the opinions of credit ratings agencies like Moody’s, Standard & Poor’s and Fitch Ratings. These turned out to be overly rosy, and investors suffered hundreds of billions in losses when the loans underlying these securities went bad.