Craxi was considered Berlusconi's mentor thanks to his opening to private television in Italy from a state monopoly.
Former seven-time Christian Democrat premier, Giulio Andreotti, was convicted of involvement in a Mafia-murder. But he was cleared on appeal and never went to jail.
In the other trial playing out in the Milan courthouse, Berlusconi is charged in that case with paying for sex with an underage woman and trying to cover it up. He denies wrongdoing.