Six scientists convicted of manslaughter for advice they gave ahead of the deadly L'Aquila earthquake in 2009 today were definitively acquitted by Italy's Supreme Court of Cassation in Rome following lengthy deliberations by a panel of five judges. But the court upheld the conviction of a public official tried alongside them.

The ruling marks the end of a 5-year legal process that has proven immensely controversial in the scientific world and beyond. In 2010 the seven were placed under investigation for allegedly giving false and fatal reassurances to the people of L'Aquila a few days ahead of the earthquake, which struck on 6 April 2009, killing 309. The seven were put on trial a year later and in 2012 were each handed 6-year jail sentences. At an appeal last year, however, six of them—three seismologists, a volcanologist, and two seismic engineers—were acquitted. The seventh, Bernardo De Bernardinis, who at the time of the quake was deputy head of Italy's civil protection department, remained convicted but with a reduced jail term of 2 years.

The hearing at the Court of Cassation, which started yesterday, took place after appeals prosecutor Romolo Como asked that the convictions be reinstated. Although that possibility appeared remote, the five-judge panel, headed by Fausto Izzo, remained closed in their chamber for 10 hours before confirming the lower court’s decision.

Following the verdict, Alessandra Stefano, who represented University of Pavia seismic engineer Gian Michele Calvi, said that "justice has finally been done." The convictions, she maintained, had "cried vendetta."

One of the other scientists to be acquitted, the then-president of Italy's National Institute of Geophysics and Volcanology Enzo Boschi, told ScienceInsider that he was "very tired" but "very relieved." He and another of the six experts put on trial, Giulio Selvaggi, he said, had their "consciences in place."

The victims' relatives had a different view. Maurizio Cora, whose wife and two daughters were killed, argues that all seven of those tried are guilty. "If they had said there was a risk they would have done their job," he said. "But they didn't have the balls to say that."

The seven scientists took part in a meeting of an official advisory committee in L'Aquila on 31 March 2009, called to analyze the danger posed by an ongoing series of small- and medium-sized tremors that had shaken the town for several months. The judge in the original trial, Marco Billi, concluded that the experts carried out a "superficial, approximate and generic" risk analysis that persuaded townsfolk that they would be safe indoors on the night of the earthquake, with fatal results. The scientists, he said, were guilty not of failing to predict the quake, but of failing to discharge their duties under the law.

That reasoning was described by Fabrizia Francabandera and two other judges in L'Aquila's appeals court as "uncertain and fallacious." Instead, said Francabandera and her colleagues, Billi should have scrutinized the scientific content of the commission members' analysis. The experts, they ruled, could not be faulted for saying there was no reason to think that the risk of a major earthquake had increased following the earlier tremors. (Many other seismologists, however, say that the risk actually can rise after such tremors.)

Prosecutor Como in turn criticized the appeals judgment. In asking the Court of Cassation to review the verdict, he said that the appellate judges should have held the scientists to account for failing to object to the idea of an energy discharge. At the original trial, many witnesses described how their loved ones had been persuaded to stay indoors after De Bernardinis told a journalist, during a now infamous interview ahead of the commission's meeting, that the ongoing tremors were favorable because they discharged energy and therefore made a larger quake less likely.

Most scientists reject the discharge idea, and Como pointed out that when the experts were asked what they thought of it during the meeting, they said nothing. "Why on 31 March did no one dissent, no one jump up out of their seat, no one explain to the other people present of the scientific consensus that that was nonsense and not a positive signal?" he demanded.

However, Cassation prosecutor Giuseppina Fodaroni, whose role was to analyze the legal validity of the appeals court's judgment, took a very different view. Only De Bernardinis was guilty of having reassured the public, she said, having made his reassuring comments before the committee's meeting. What's more, she claimed, the message from the other experts during the meeting—that the chance of a major quake had neither increased nor decreased—was "neutral" and therefore not reassuring.

That message, she argued, should have caused De Bernardinis to be more cautious in statements he made after the meeting, among them that no larger tremors were expected to occur. She argued, successfully, that his conviction should be upheld.

As judgment was being passed in Rome today, a parallel manslaughter trial against Guido Bertolaso, head of the civil protection department in 2009, was postponed until 4 March. That trial centers on a phone call Bertolaso made to a local official in setting up the commission's meeting, in which he said he was sending the experts to L'Aquila on a "media operation" to reassure the public and "shut up" a technician in the nearby Gran Sasso nuclear physics laboratory who had allegedly made a series of alarming predictions of imminent strong earthquakes.