The MF Global investigation, and search for as much as $1.2 billion in customer funds, may have taken a giant leap forward.  Federal authorities reportedly uncovered e-mails that appear to detail money transfers during the firm’s final days - including transfers containing customer money. One e-mail chain refers to the transfer of about $200 million that MF Global owed JPMorgan Chase on 10/28/11 - the Friday before the firm filed for bankruptcy.  In that chain, a senior official in the firm’s Chicago office was told to make the transfer, according to people close to the investigation. Edith O'Brien Enters the Picture. That official, Edith O’Brien, is a treasurer at MF Global, and considered a “person of interest” in the investigation.  It's expected that she'll be interviewed in the coming days.  That would be helpful, because it was not clear who had directed Ms. O’Brien, whose job it was to oversee customer money.  Nevertheless, she made the $200mn transfer on 10/28 that to be entirely customer money. Lawyering Up. Ms. O’Brien, who's playing it safe, has hired prominent criminal defense lawyer, Reid Weingarten of Steptoe & Johnson.  She has not been accused of any wrongdoing, and there's no indication she had reason to suspect that the money being transferred included customer money.  [C-I Note: That last comment sounds nonsensical, given the fact that she was responsible for overseeing customer money.] In any case, MF Global’s sloppy bookkeeping and the flurry of transactions in its final days may have obscured the fact that the firm was dipping into the cash of farmers, traders and hedge funds to cover its own needs. Still, Dealbook surmises that Ms. O’Brien and the e-mails may be the missing links in their 2-month old search for customer funds - whether or not she was aware of the possible implications of her actions.  She appears to have been at the "center of the action" - and the world can hardly wait to learn what light she may shed on an investigation that, to date, has not been able to find a "smoking gun" or, at a minimum, the "trace of a scent." Ms. O’Brien could not be reached for comment. Mr. Weingarten did not respond to several requests for comment. A spokesman for the Commodity Futures Trading Commission, which is leading the investigation, declined to comment. Attorney Weingarten: Long List of Distinguished Clients. Mr. Weingarten, a former Justice Department official, has also represented Bernie Ebbers, former CEO of WorldCom, and other top corporate executives.  Earlier this year, Goldman CEO Lloyd Blankfein, hired Mr. Weingarten. And What About the Rest of the Missing Customer Funds - Some $1 Billion? From the get-go, investigators have said that customer funds - possibly ranging from 600mn to $1.2bn - is missing.  The $200mn transfer that Ms. O'Brien processed doesn't begin to account for this large amount. However, investigators now suspect that MF Global continued using customer money on 10/28 to settle margin and/or collateral payments with trading partners and others, leaving a $1bn hole. It's understood that JPMorgan advised Corzine during the final days that it would not consider purchasing any of MF Global's bonds until the firm helped clean up overdrafts in firm accounts at the bank in London.  The bank also asked for a guarantee as to the source of the money that MF Global had been using to pay off its trade obligations. Corzine passed those requests to others in MF Global, including General Counsel Laurie Gerber, who refused to provide a written guarantee, saying the firm didn't offer such special assurances. Two days later, at about 6 p.m. on Sunday, 10/30, Ms. Ferber notified regulators that there was an apparent shortfall in customer money.  She blamed an accounting error, according to the CME Group, the firm’s primary regulator and an exchange where it conducted business.  At about 1 a.m., Ms. O’Brien and another executive in Chicago told the exchange that the shortfall in the customer accounts was real, according to the CME. Ms. O’Brien is considered an expert of sorts on the protection of customer money at futures firms.  In the last year and a half, she's made several appearances before the CFTC.  On at least 2 occasions, she was a panelist at roundtable discussions held at the agency on the topic of safeguarding customer money, and she attended at least 3 meetings with agency officials, including one titled “Practicalities of Individual Customer Protection.” Since MF Global’s collapse, Ms. O’Brien has been working for the trustee overseeing the liquidation of the firm’s brokerage unit, helping lawyers and accountants understand the firm’s operations. For further details, go to:   [DealBook, 12/20/11].