For the police, it was El Dorado of illegal payoffs.
Illegal payoffs may create conflicts of interest that skew deals in hidden ways.
Advisers to Mr. Estrada noted that Mr. Singson, who says he made illegal payoffs to the president, was hardly a reputable witness.
Mr. Rezko, who is in jail in Chicago, was convicted in June of exacting illegal payoffs from companies seeking business with Illinois.
At the Amu Darya oil field in June, President Karzai's government accused a rival, the warlord Gen. Abdul Rashid Dostum, of putting pressure on the Chinese oil company to make illegal payoffs.
The suspect, a 48-year-old man, is the sixth person to be arrested in Scotland Yard's investigation into illegal payoffs by newspapers to police officers in the wake of the phone hacking scandal at The News of the World.
Mr. Hofheinz, who was mayor from 1974 to 1977, was indicted last year on charges of making $1.5 million in illegal payoffs to Cecil Brown, an Edwards associate, in a bid to make three business deals in Louisiana starting in 1993.
As reported in a front-page article in The New York Times this week, the Wal-Mart Mexican bribery scheme has all the makings of a gripping criminal prosecution: millions of dollars in illegal payoffs to Mexican government officials and evidence of a cover-up scheme that went all the way to Wal-Mart headquarters in Bentonville, Ark.
Even if firms have an obligation to refrain from making illegal payoffs, does this obligation actually matter in the real world?
Presented with a report detailing the illegal payoffs, Walmart's senior managers rejected the investigators' call for a full inquiry.
