Joaquim Barbosa, the tough justice overseeing Brazil's high-profile corruption trial, was officially nominated president of the Supreme Court, the first black to assume the post.

In a plenary session, the court's 10 justices picked the 58-year-old Barbosa, the most senior member, to assume the rotating presidency for a two-year term.

He will formally take his post in the coming weeks.

In a country, where more than half of the 194-million-strong population is of African descent, Barbosa is the only black on the court.

The low-key justice has shot to fame as the most vocal critic of the congressional vote-buying scheme laid bare in the ongoing "Mensalao" (big monthly payments) trial of former top aides of ex-president Luiz Inacio Lula da Silva;

Tuesday, six of the court's 10 judges found Lula's ex-chief of staff Jose Dirceu guilty in connection with the scheme, which ran from 2002 to 2005 during the popular president's first term.

The head of Lula's ruling Workers' Party (PT) at the time, former guerrilla Jose Genoino, and its treasurer, Delubio Soares, were also convicted on charges of corruption.

The trio, who are among 37 former ministers, lawmakers, businessmen and bankers on trial before the Supreme Court, were said to have distributed money to lawmakers to "illegally secure the support of other political parties to form a ruling government coalition."

The trial, which is receiving blanket media coverage, has mesmerized the nation since it opened in early August and Barbosa has emerged as a folk hero for his uncompromising stance even though he was nominated to the court by Lula in 2003.