Rome - Italy's top court begins crucial hearings for former prime minister Silvio Berlusconi on Tuesday that could end the billionaire tycoon's parliamentary career and risk upsetting the country's fragile coalition.
The Supreme Court is set to decide whether or not to confirm a one-year prison sentence and a five-year ban from politics in a long-running tax fraud case involving Berlusconi's media business interests.
"Judgment Day", reads a headline in Italy's top-selling Corriere della Sera daily, while La Stampa said in an editorial that the case was like "a giant boulder that is paralysing the entire political framework".
"This is more than a simple verdict," La Stampa said.
The final appeal hearing is expected to start later on Tuesday but Italian media reported that the actual verdict may come only on Wednesday and there is a possibility that the case could be adjourned until September.
The verdict will be a milestone in the history of legal woes and sex scandals that have dogged Berlusconi's 20 years on the Italian political scene including three terms as prime minister.
In other court cases, Berlusconi has been convicted of having sex with an underage prostitute, abusing his powers as prime minister and publishing a secret police wiretap to damage a political rival.
He denies all charges and is appealing against those rulings, accusing prosecutors of being politically biased and pursuing a vendetta against him.
Even if the court upholds Berlusconi's tax fraud conviction, the Senate would still have to vote to allow the sentence to be implemented since Berlusconi has a seat in the upper house of parliament.
Legal experts say there is virtually no chance of Berlusconi being sent to prison because of lenient sentencing guidelines for over-70s in Italy.
There is however a possibility that the media magnate could be put under house arrest in his luxury villa in Milan or placed in the care of social services.
The political ban would eject the 76-year-old from the Senate and prevent him from running for office.
Berlusconi could however remain as a figurehead leader of his centre-right People of Freedom party.
The court could also acquit Berlusconi entirely or send the case back to the appeal courts for another trial - a move that would effectively mean the case expiring under a statute of limitations.
In an interview published on Sunday by the newspaper Libero, Berlusconi sounded nervous but bullish.
"I am quite optimistic, they cannot find me guilty," Berlusconi said. He added however: "I haven't slept for a month. I wake up at night and stare at the ceiling, thinking about what they've done to me".
He also emphasised that he would "not go into exile" like one of his predecessors and political mentors, Bettino Craxi, who fled to Hammamet in Tunisia and was convicted of corruption in the early 1990s.
Berlusconi has said he does not want the ruling to have an impact on the government, a coalition between right and left forged after two months of political stalemate following February elections.
But some of his diehard supporters are taking a harder line and are threatening mass resignations from parliament, a move that could trigger fresh elections.
Stefano Folli, a columnist for the Il Sole 24 Ore business daily, said the verdict had "destabilising potential".
"A convicted Berlusconi would be a martyr for his people but would also be an unacceptable ally for a large part of the left," he said.
Christian Schulz, senior economist at Berenberg bank, said: "A verdict against Berlusconi would increase the likelihood of new elections".
"But neither Berlusconi nor [Prime Minister Enrico] Letta should have a strong reason to end the coalition," he said.
Berlusconi has often been dismissed as a political player in the past only to re-emerge.
Many had written him off when he was ousted from power at the end of 2011 by a parliamentary revolt and a wave of panic on the financial markets.
But he staged an impressive comeback in this year's general election, with his coalition coming an extremely close second to the main centre-left grouping with nearly a third of the vote.