Tuesday's verdict marked the final fall from grace for Dirceu, who was once considered a top contender to succeed Silva.
He entered politics as president of the leftist National Students Union and resisted Brazil's 1964-85 military dictatorship, which arrested him in 1968. The following year, an anti-regime group kidnapped U.S. Ambassador Charles Elbrick and demanded the release of 15 imprisoned guerrillas, including Dirceu. Soon after arriving in Mexico he traveled to Cuba, where he had plastic surgery to change his looks and underwent guerrilla training.
Dirceu then sneaked back into Brazil and lived covertly, not even revealing his true identity to the woman he married. Only after the government decreed a political amnesty in 1979 did he go public, helping found the Workers Party with Silva, then a leftist labor union leader.
Though Dirceu maintained his innocence throughout, he resigned as Silva's chief of staff and was expelled from congress after allegations surfaced in 2005.
Silva tapped current President Dilma Rousseff to replace Dirceu as his chief of staff.
Rousseff, who had never held elected office before, won the presidency in 2010 after being anointed Silva's chosen successor.
The "mensalao" scandal has not hit Rousseff's reputation. She's seen as being tough on corruption after pushing out seven of her own Cabinet ministers after allegations of various misdeeds arose in the Brazilian press.
Associated Press writer Bradley Brooks in Sao Paulo contributed to this report.