Updated

Former Gov. George Ryan's (search) closest political adviser and top aide for a decade pleaded guilty Tuesday to mail fraud and agreed to cooperate in the government's corruption investigation of his former boss.

In exchange for the plea, authorities agreed to drop five other fraud charges against Scott Fawell (search), who is already serving a 6 1/2-year prison sentence for racketeering.

Fawell has been under pressure for years from prosecutors who want more information about Ryan. In the past, he has said he knows nothing, but the plea agreement requires him to cooperate and means he will not be sentenced until after Ryan's racketeering trial, expected to be held next year.

The latest charges against Fawell involved alleged bid-rigging at the Metropolitan Pier and Exposition Authority (search), where he was once the $199,000-a-year chief executive. The authority operates the McCormick Place (search) exposition center on Chicago's downtown lakefront.

Fawell, 47, was accused of telling the facility's director of operations to leak sealed bidding information to a lobbying firm representing a St. Louis company involved in an $800 million expansion of McCormick Place. The company was able to significantly lower its bid and still land an $11.5 million contract to oversee the expansion.

Under his plea deal, which still requires a judge's approval, Fawell will get a maximum 3 1/2-year sentence to run concurrent with the 6 1/2 years he is already serving. He also could get a six-month reduction of his current sentence.

The government's corruption investigation has targeted dozens of former state employees and reached as high up the political chain as the former governor.

Fawell's current sentence is for using state employees and taxpayer dollars to fuel Ryan's political campaigns throughout the 1990s. He masterminded Ryan's two successful campaigns for Illinois secretary of state and his 1998 race for governor.

He was Ryan's chief of staff in the secretary of state's office. After Ryan became governor, Fawell went to the Metropolitan Pier and Exposition Authority.

Ryan was indicted in December on charges of racketeering conspiracy, mail fraud, tax fraud, filing false tax returns and making false statements as part of the government's six-year investigation. He has pleaded innocent.

The investigation, dubbed Operation Safe Road (search), began as an inquiry into bribes paid in exchange for driver's licenses and evolved into a wide-ranging investigation of political corruption when Ryan was secretary of state and later governor.