Senator Cesare Previti, a close aide of former premier Silvio Berlusconi, was convicted of corruption by a Milan appeals court on Friday and sentenced to one year and six months.
The court found the 72-year-old senator guilty of judge bribery in a complex trial involving Fininvest, Berlusconi's family holding company.
Previti, Berlusconi's former attorney and one-time defence minister, is expected to appeal the sentence.
Under Italy's three-tier justice system, defendants have a right to two appeals before a sentence is considered definitive.
Previti and Fininvest members were accused of bribing a judge to win control of Italy's biggest publishing company Mondadori from Berlusconi's archrival Carlo De Benedetti in 1991.
Prosecutors say Fininvest paid some 400 million lire to Vittorio Metta, the key judge in the final ruling.
Two Rome attorneys, Attilio Pacifico and Giovanni Acampora, along with Previti, were the go-betweens in the affair, prosecutors claim.
The Milan appeals court found Pacifico, Acampora and Metta guilty, sentencing the first two to one year and six months each and Metta to two years and eight months.
In 2001, Berlusconi was acquitted in the same trial, with an appeals court ruling that while a case existed against Berlusconi for simple corruption, the statute of limitations for the crime had already expired.
In May 2005, an appeals court overturned earlier convictions against Previti, Pacifico, Acampora and Metta, declaring all four of them not guilty.
But a year later, the Supreme Court ruled in favour of the prosecution's appeal against the acquittals and ordered a retrial, which began in December 2006.
The Mondadori case is complex because it was bundled together with another corruption trial involving the same defendants.
In that trial, Previti was accused of passing on a huge bribe from oil company SIR to gain a billion-lire settlement from public financial holding company IMI, which has since been privatised.
The senator was definitively convicted in that trial in May 2006 and sentenced to six years.
If Previti is definitively convicted in the Mondadori case, the sentence will be added to the one he received in the IMI-SIR trial.
The senator, a member of Berlusconi's Forza Italia party who was re-elected last year, has been under house arrest since his conviction.
However, he recently benefitted from a prisoner pardon approved by parliament which cut his sentence by three years.
Earlier this week, a Rome court approved the senator's request that the remainder of his sentence - one year and seven months - be commuted to community service.
Previti will now act as a legal consultant for a Catholic organisation based in Castelo Gandolfo near Rome which helps former drug addicts.
The senator is awaiting a definitive sentence in another judge bribery trial.
Two lower courts in Milan have found Previti guilty of bribing a judge in a case stemming from the blocked 1985 sale of the SME food conglomerate, owned by state holding company IRI, to CIR, a group owned by De Benedetti.
Previti was found guilty of paying co-defendant Renato Squillante, a former chief Rome magistrate, a bribe of $434,000 in 1991.
Berlusconi was acquitted in the same trial in December 2004, on one count because of the statute of limitations.
The Supreme Court overturned Previti's convictions in a surprise ruling last November, saying that for technical reasons, the trial should have been held in Perugia and not Milan.
Previti has always denied wrongdoing and insists, like Berlusconi, that he is the victim of a judicial witch-hunt by "politicised" magistrates.
Berlusconi, who is Italy's richest man, has been at the centre of numerous corruption investigations into his vast business empire.
He has never received a definitive guilty verdict but in some cases he has been cleared because of the statute of limitations or changes to the law introduced when his coalition was in power.
Berlusconi is currently on trial in a corruption case also involving British corporate lawyer David Mills, the estranged husband of Britain's Culture Secretary Tessa Jowell, and 12 other defendants.
The trial, which began in November, centres on alleged fraud at Berlusconi's private TV network company Mediaset.
