Giovanni Brusca turned state witness three years ago

Enzo Brusca was let out of prison, after agreeing to turn state witness.

Brusca - who had strangled an 11-year-old boy and disposed of the body in an acid bath after the boy's father implicated him in a murder - has served only seven a 30-year sentence.

He is a good person, one who has fully and sincerely repented Alfonso Sabella Investigating judge

In Italy, jailed Mafia members are often offered lenient sentences to encourage them to talk, but the Brusca decision has re-ignited widespread opposition to the policy.

Critics claim that Mafia prisoners are unreliable witnesses.

"This decision calls for divine retribution," said Roberto Calderoli, deputy speaker of the Senate. "It insults the conscience of all good people."

The controversy prompted Justice Minister Roberto Castelli to order an inquiry into Brusca's release from jail on Monday.

But the judge in charge of the inquiries which led to Brusca's arrest in 1996, Alfonso Sabella, told Italian TV that he was "basically a good person" who had genuinely repented.

Brusca confessed to the crime, saying that it was committed on the orders of his brother Giovanni.