When $1.6 billion of customer money goes missing, you'd think it would be easier to punish someone for it.

Not so at MF Global, the brokerage firm that misplaced the impressive 10-figure sum around the same time that it declared bankruptcy in October. The missing money has since been found, but identifying the parties responsible for the episode has proved more difficult.

As The Wall Street Journal reports this week, many senior executives at MF Global -- including finance chief Henri Steenkamp, treasurer Vinay Mahajan and assistant treasurer Edith O'Brien -- aren't even registered with regulators, meaning they can't be formally charged with a failure to supervise in the missing-money case.

Regulators had been looking especially closely at Steenkamp lately, asking why he claimed at one point to know little about the missing funds when company e-mails show that he was in the same loop as everyone else.

O'Brien, too, has been singled out by people looking into the matter. In March, at a Congressional hearing, O'Brien pled the Fifth Amendment when asked about her role in the transfer of $200 million in customer funds.

But since former CEO Jon Corzine was the only MF Global employee registered with the Commodity Futures Trading Commission last October, neither Steenkamp nor O'Brien can be held responsible for a failure to supervise, the WSJ reports.

Those two may face challenges from another direction, though. James Giddens, the trustee tasked with recovering and returning the customer funds, said last week that he's considering bringing a civil suit against Corzine, Steenkamp and O'Brien for negligence.

With the CFTC's workload about to swell as a result of additional responsibilities, it's unclear how much attention the agency will be able to devote to MF Global's key players anyway. Gary Gensler, chair of the commission, recently expressed dismay over a Republican-backed bill to cut the CFTC's funding by about 12 percent in spite of an expanding duties.

Here is a timeline of MF Global's collapse:

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  • Lost Customer Funds Found

    James Giddens, the trustee overseeing the liquidation of MF Global, told the Senate Banking Committee in April that $1.6 billion worth of lost customer funds had been found and his analysis <a href="http://www.huffingtonpost.com/2012/04/25/mf-global-missing-customer-money-accounted-for_n_1452128.html?ref=business" target="_hplink">"is substantially concluded,"</a> CNNMoney reports.

  • Jon Corzine Takes the Reins at MF Global

    In a big turning point for the brokerage firm, in 2010 MF Global Holdings hired Jon Corzine, a former chief executive at Goldman Sachs, former U.S. senator and former Governor of New Jersey. Corzine returned to the financial industry after losing his gubernatorial reelection bid to Chris Christie in 2009.

  • Leveraged Bets on European Debt

    Jon Corzine made risky moves in his mission to turn MF Global into a big Wall Street player. After a period of aggressive trading didn't earn the profits Corzine had hoped for, the firm delved into the foreign debt market, making $6.3 billion worth of large and heavily leveraged bets on distressed sovereign debt in troubled European countries like Spain and Italy.

  • Bankruptcy

    Europe's economy continued to melt. MF Global investors panicked when they caught wind of the billions in leveraged bets, and on Oct. 31 MF Global filed for bankruptcy. It was called the first American financial casualty of the European debt crisis.

  • Federal Investigation

    During the firm's collapse, federal regulators discovered that $630 million in customer money couldn't be accounted for. A federal investigation ensued, and forensic accountants found the amount was actually closer to $1.2 billion. Experts suspected the client money was used inappropriately for company purposes.

  • Lobbying

    The investigation shed light on Jon Corzine using his personal influence in Washington to lobby against restrictions on how firms can invest customer money.

  • Corzine Resigns

    On Nov. 4, four days after the firm filed for bankruptcy, Jon Corzine voluntarily stepped down. He had not been accused of any wrongdoing.

  • 'MF Global Rule'

    In early December federal regulators adopted the 'MF Global rule' to prevent other firms from using client funds to buy sovereign debt. Regulators restricted the transaction that allowed MF Global to borrow money from its own customers.

  • Corzine Testifies Before Congress

    On Dec. 8 Jon Corzine testified before Congress on the missing money. Speaking to his former colleagues in the Senate, Corzine said he was "stunned" by the missing client funds. He offered an apology but said, "I simply do not know where the money is."

  • Developing Case

    Corzine testified that he didn't know any customer money was missing until the day before the firm filed for bankruptcy. But a financial executive<a href="http://www.huffingtonpost.com/2011/12/13/jon-corzine-testimony-_n_1146192.html?ref=business " target="_hplink"> claimed</a> Crozine "was aware" of a $175 million transfer from customer accounts to a European affiliate of the firm.

  • $200 Million Transfer Of Customer Funds

    Ex-CEO Jon Corzine allegedly authorized the transfer of around $200 million in customer funds to pay down an overdraft just days before the firm collapsed, <a href="http://www.bloomberg.com/news/2012-03-24/mf-global-s-corzine-ordered-funds-moved-to-jp-morgan-memo-says.html" target="_hplink"><em>Bloomberg</em></a> reported in February.

  • Pleading The Fifth

    MF Global executives <a href="http://www.huffingtonpost.com/2012/03/28/mf-global-hearing-executives-millions-customer-funds_n_1386701.html" target="_hplink">denied having significant knowledge of an authorized transfer of around $200 million</a> in customer funds to avoid an overdraft. Edith O'Brien, an executive who wrote an email about the transfer at the time, <a href="http://www.huffingtonpost.com/2012/03/28/former-mf-global-executive-edith-obrien-5th-amendment_n_1386210.html" target="_hplink">invoked the Fifth Amendment</a>.