The verdict, ending a three-and-a-half-year trial, was read to a packed court with solemn aplomb by Judge Giancarlo Orzella. Rosita Pecorelli, the sister of the dead journalist, collapsed in tears, saying her brother has been betrayed.
But the acquittal was little surprise to anyone who has tracked the 80- year-old life senator's remarkable ability to remain at the centre of one of the most corrupt power systems in the Western world.
His co-defendants - former foreign trade minister Claudio Vitalone, convicted Mafia bosses Gaetano Badalamenti and Pippo Calo, Mafia hitman Michelangelo La Barbera and common criminal Massimo Carminati - were also acquitted by the jury of two magistrates and six members of the public, among them a pensioner, a vending machine salesman and a textile worker.
While the charges against Mr Andreotti were startling - commissioning the Sicilian Mafia to eliminate a vituperative journalist seemingly bent on destroying him - the prosecution had two important difficulties. First, the evidence itself was largely based on the testimony of six mafiosi informers and could not easily be corroborated through documentation or cross-examination of unfriendly witnesses.
Second, and arguably more influential, was Mr Andreotti's extraordinary standing in Italian society. Having been briefly reviled as the figurehead of a corrupt and morally bankrupt generation in the early 1990s, when the old Christian Democrat-led political elite crashed amid a welter of corruption scandals, the wily old man - who spent 46 years in government - has brilliantly stitched his reputation back together again.
He has spent the past three years basking in the limelight due a beloved elder statesman, attending state dinners and society cocktail parties and enjoying the attention of influential journalists.
Conversely, the reputation of the magistrates who sought to bring him to justice - not just in Perugia, but also in Palermo, where he is standing trial on separate charges of criminal collusion with Cosa Nostra - has been in steady decline. Their reliance on informers has been increasingly dismissed on the basis that convicted criminals and murderers cannot be trusted.
Mr Andreotti has thus managed a remarkable revision of Italian history, minimising his role in some of the most egregious abuses of political power, and in the process preventing Italy from staring in the face its most shameful historical episodes.
Those episodes almost all stem from Italy's pivotal role in the Cold War and the desperate measures used to exclude Europe's largest Communist Party from government. With backing from the CIA and Nato, the Christian Democrats allowed the Mafia to flourish after the Second World War as a bulwark against Communism in Sicily.
By the late 1970s, with the Communist Party's popularity at its peak, the abuses extended not just to an increasingly powerful Sicilian Mafia - which was directing its considerable muscle towards the Andreotti faction in the Christian Democrats - but also to right-wing terrorist groups with links to the secret services and government infiltration by a secret Masonic sect known as P2.
The greatest tragedy of the period was the kidnap and murder of the moderate Christian Democrat Aldo Moro by the Red Brigades in 1978. Mr Moro had just negotiated a government in which the Communists would participate from the sidelines. That was hurriedly dropped by Mr Andreotti, who became prime minister on the day of the kidnap and later refused to negotiate for Mr Moro's release.
Mino Pecorelli, the investigative journalist murdered the following year, was one of many voices who suspected that the Christian Democrats deliberately allowed Mr Moro to be killed. In dispatches for his agency, later turned into a magazine called Osservatore Politico, he accused Mr Andreotti of colluding with the Mafia, calling him "Don" and "Godfather". He had predicted a bad end for Mr Moro as early as 1975, and claimed at the time of his death to possess damaging information about Mr Andreotti's role in his abduction.
Mr Pecorelli, the court was told in the trial, had amassed a dossier that could have incriminated Mr Andreotti and finished his political career.
What that information was will never be known. Not only was Mr Pecorelli gunned down in front of his offices, but his apartment was turned upside down and some of his papers possibly stolen or destroyed. The magistrates prosecuting Mr Andreotti sought to show a chain of responsibility linking him with the Sicilian Mafia, and the Mafia with the alleged gunmen, but several pieces of the puzzle were missing - not just Mr Pecorelli's information, but also witnesses who have since died or been killed.
The half-truths and rumours swirling around the Pecorelli affair are typical of almost every episode in Mr Andreotti's career - allowing him to protest his innocence and a certain amnesia at every turn, and express consternation at the constant accusations against him.
"I've often asked myself why I, of all people, should be considered the sly, jealous custodian of so many dark secrets," he wrote in a memoir. "Perhaps one reason is the necessity many people feel to justify their own many inadequacies and omissions."
Senator Andreotti stayed away from court yesterday, spending his day of judgement like any other; attending morning mass at a Rome chapel near his home, seeing to his political chores at the Senate and then returning home for lunch and a nap. Last night he could take heart from Italy's justice system as he contemplated the next case: a Palermo court will decide next month whether he is guilty of complicity with the Sicilian Mafia. Meanwhile, the prosecutors in the Pecorelli case have said they will appeal.
Ask just about any Italian if they accept Mr Andreotti's version of history and they will laugh out loud. The fact that the old man has never been nailed for any wrongdoing, however, is testimony both to his own cunning and to a certain failure of nerve by a country that has identified so closely with his brand of power-wielding that to condemn him would ultimately be to condemn themselves.