A Milan appeals court has explained why it upheld Silvia Berlusconi's tax fraud conviction, saying the politician illegally purchased the rights to broadcast U.S. movies on his private TV network, then falsely declared the payments to avoid taxes.

The court made its ruling May 8, and on Thursday it followed the Italian judicial procedure of explaining the motivation for upholding the conviction and four-year sentence.

It said Berlusconi was one of two people "responsible at the head of this illegal operation" to purchase the rights to broadcast U.S. movies on Berlusconi's private TV network, falsely declare the payments to avoid taxes, and hide money offshore and off the books of his holding company.

Berlusconi is expected to appeal to Italy's highest court.