"Regulators' enforcement divisions and the Justice Department will work together because if the money is missing, somebody did something wrong," Greenberger said.
And given the damage done by MF Global's failure, there's little Corzine can do to revive his public image, said Michael Robinson, a former SEC official who now works in crisis communications.
"Unless Jon Corzine can look under the mattress in his house and find $1.2 billion to give back to customers, his reputation is beyond repair," Robinson said.
He noted that Corzine spent a career branding himself as an effective manager. Corzine rose from the trading floor of Goldman Sachs to become the investment bank's co-chairman. He then ran successfully for the U.S. senate and one term as governor of New Jersey. Corzine joined MF Global shortly after losing his bid for a second term.
Now, to protect himself legally, Corzine must avoid being precise about what occurred at the firm he led until last month. That's why many legal experts had expected Corzine to invoke his Fifth Amendment right against self-incrimination. He never did.
Much of Corzine's testimony Thursday involved an allegation that he knew about customer money that may have been transferred to a European affiliate just before MF Global collapsed.
"I did not instruct anyone to lend customer funds to MF Global or any of its affiliates," Corzine told a House panel. He also said he didn't know about "the use of customer funds on any loan or transfer."
It was his first public appearance since Terrence Duffy, CME Group Inc.'s executive chairman, alleged Tuesday that he might have known about the $175 million transfer. MF Global traded on exchanges managed by CME Group.
According to Duffy, an MF Global employee told a CME auditor that "Mr. Corzine was aware" of the earlier transfer. Duffy said he referred the matter to the Justice Department and the Commodity Futures Trading Commission.
The transaction Duffy described wasn't necessarily illegal. Brokers such as MF Global are allowed to borrow from customer accounts temporarily in some circumstances — to reduce their own risk, for example.
But such cases are a narrow exception. A firm couldn't use customer money to pay trading partners if its speculative trades lost value. Even in cases where borrowing clients' money was legal, the firm would have to replace it with a safe, cash-like investment such as a U.S. Treasury security.
Corzine also was questioned about whether he used his relationships with regulators to gain advantages for MF Global.
Corzine has been a major fundraiser for Democrats. He was co-chairman of Goldman Sachs Group Inc. In that role, he worked with two other Goldman executives at the time: Gary Gensler, now chairman of the CFTC, and William Dudley, now president of the Federal Reserve Bank of New York.
Gensler has recused himself from the investigation because of his long history with Corzine. Along with other Wall Street executives, Corzine lobbied Gensler and his staff last summer against a possible CFTC rule that would limited how their firms can invest clients' money. Afterward, the CFTC delayed adopting the rule until earlier this month.
Early this year, the Federal Reserve allowed MF Global to join an elite group of 22 dealers that help the government sell Treasury securities. The Fed did not assess MF Global to see if it was taking on too much risk. Instead, Fed officials relied on oversight by the CFTC, the SEC and others.