Those are considerable victories. Four other cases she cited through her colleague involved Ponzi schemes and fraud by small investment advisory firms, not household-name Wall Street or financial firms.

A review of her years in the Southern District also turned up several intriguing cases that Ms. White and her colleagues did not pursue or turned away. All three of these matters involved large and prestigious financial companies headquartered in the United States.

A big question mark, federal investigators say, still hangs over the decision by Ms. White’s office not to prosecute Citibank in the mid- to late 1990s for a possible role in questionable money transfers that benefited Raúl Salinas de Gortari, the brother of the former president of Mexico. Between 1992 and 1994, Mr. Salinas, a consultant to a Mexican antipoverty agency whose annual salary never exceeded $190,000, somehow moved almost $100 million from Citibank accounts in Mexico and New York to Citibank accounts in London and Switzerland.

Banks have a legal obligation to prevent money-laundering, and in July 1996, Ms. White’s office opened an investigation into the Salinas transactions. But no prosecution against the bank or any of its officials involved in the Salinas accounts ever came.

A report by the Government Accountability Office in October 1998, as well as a subsequent inquiry by the Senate’s Permanent Subcommittee on Investigations, shed light on what can only be described as disturbing practices at Citibank. Its actions, the report said, helped Mr. Salinas transfer money in a way that “effectively disguised the funds’ source and destination, thus breaking the funds’ paper trail.” Citibank made $2 million in fees on the Salinas accounts, the Senate investigators found.

Mr. Salinas was arrested in February 1995 on suspicion of murdering his former brother-in-law, who had been a leading politician in Mexico. Senate investigators said the bank’s “initial reaction to the arrest was not to assist law enforcement but to determine whether the Salinas accounts should be moved to Switzerland to make discovery of the assets and bank records more difficult.” Mr. Salinas was convicted of the murder in 1999.

As it prepared its report in 1998, three years after Ms. White’s investigation into Citibank began, the G.A.O. requested information from federal prosecutors on the case. The G.A.O. was rebuffed. “Limited by the ongoing Justice Department investigation, we could not determine whether Citibank’s actions violated law or regulation,” the report said.