Former Berlusconi aide under investigation President Barack Obama (R) with former Italian President Silvio Berlusconi in 2010. PALERMO, Italy, July 18 (UPI) -- A former aide to ex-Italian Prime Minister Silvio Berlusconi is under investigation for allegedly extorting money from Berlusconi, judicial sources say. The Italian news agency ANSA, citing judicial sources, said the former aide, Marcello Dell'Utri, is being investigated in Palermo. Dell'Utri is scheduled for a retrial after being sentenced to seven years in jail for allegedly helping the Mafia. The supreme Court of Cassation ordered the retrial in March. The court said Dell'Utri's legal rights had not been respected in the first appeal trial after his original conviction. But the court also said evidence existed showing Dell'Utri had acted as an intermediary with organized crime for Berlusconi, passing on "substantial sums" of money for protection. Palermo prosecutors had called Berlusconi for questioning in the case Monday but he reportedly did not attend because of what ANSA called official business that created a "legitimate impediment." Dell'Utri serves as a senator in Berlusconi's People of Freedom party. Berlusconi is expected to run next year for a fourth term as prime minister.