MF Global Official Pleads the Fifth in Case of Missing $1.6 Billion Edith O'Brien, assistant treasurer with MF Global Inc., is sworn in before invoking her Fifth Amendment right against self-incrimination at a House Financial Services subcommittee hearing in Washington D.C. on Wednesday, March 28, 2012. Lawmakers investigating the spectacular collapse of MF Global hit a brick wall Wednesday when none of the company executives called to testify appeared to know anything about what went wrong at the firm, or the whereabouts of $1.6 billion in client funds that remains missing. One after another, senior MF Global executives denied knowledge of, and responsibility for, the eighth largest bankruptcy in U.S. history. The hearing's star witness, meanwhile, invoked her Fifth Amendment right against self-incrimination. Former MF Global Assistant Treasurer Edith O'Brien, whose name has surfaced regarding a $200 million transfer to cover an overdraft at JP Morgan Chase, refused to answer any questions before the committee. "On the advice of counsel I respectfully decline to answer based on my constitutional right," said O'Brien, who appeared to be clutching rosary beads she sat at the witness table. She was dismissed from the hearing and left with her lawyer. LIST: Top 10 Bankruptcies Other officials from the firm, including General Counsel Laurie Ferber and CFO Henri Steenkamp, repeatedly said they did not know the answers to frustrated lawmakers" questions. "Obviously there was a terrible failure here of some kind, but what it was, I don't know," Ferber said at one point. In an answer that captured the tone of the hearing, another witness, Christine Serwinski, CFO of MF Global's North American unit, said she could not recall who told her about the massive hole in the firm's books. But because so much money appeared to be missing, she didn't believe it anyway - attributing the figure to an accounting error - so she didn't tell anyone. Federal securities law requires brokers like MF Global to keep client money and firm money separate - in order to protect customers if the firm fails. On Wednesday, a New Jersey energy wholesaler said that it is owed $20 million by MF Global. More: Did Jon Corzine Lie to Congress about Missing MF Global Funds? MF Global's bankruptcy has focused scrutiny on the company's CEO during the crisis, Jon Corzine, a former Democratic senator and governor from New Jersey. Corzine, who personally engineered huge bets on European sovereign debt that went bad as the European debt crisis intensified in the fall of 2011, has maintained his innocence. In a recent statement, Corzine's spokesperson said he "never gave any instruction to misuse customer funds and never intended anyone at MF Global to misuse customer funds." Rep. Michael Capuano, a Massachusetts Democrat, was just one of several lawmakers who expressed frustration - and even anger - over the witnesses testimony. "Apparently, nobody did anything wrong, but there's more than a billion dollars missing," Capuano said, adding that the hearing reminded him of Enron. Rep. Stephen Lynch, another Massachusetts Democrat, mocked the witnesses, saying that O'Brien's pleading of the Fifth Amendment was "more helpful" than any of the other statements made by the MF Global officials. "This is absolutely disgraceful," Lynch said. It's just not believable at all. MORE: The Hubris of Jon Corzine Lawmakers had been eager to question O'Brien after uncovering an email from her stating that the transfer to JP Morgan was made, "Per JC's [Jon Corzine's] direct instructions." After the transfer, JPMorgan asked MF Global for a letter to be signed by O'Brien that would give "broad assurances that all transfers - past, present and future" complied with federal rules prohibiting customer funds from being used to cover company losses. The letter was never returned to JPMorgan after O'Brien was allegedly reluctant to sign it. But Diane Genova, JPMorgan's deputy general counsel, who also appeared, testified that Corzine nevertheless "assured" the bank that the transfer was legitimate. SPECIAL: Can Bankruptcy Work?