L'AQUILA, ITALY—Shouts of "Shame, shame!" greeted the appeals court here today after the acquittal of six scientists convicted of manslaughter 2 years ago for advice they gave ahead of the deadly earthquake that struck this central Italian town in 2009. The scientists were convicted in October 2012, and handed 6-year jail sentences, for their role in a meeting of an official government advisory panel.

Only one of the seven experts originally found guilty was convicted today: Bernardo De Bernardinis, who in 2009 was deputy head of Italy's Civil Protection Department and who will now serve 2 years in jail, pending any further appeals.

The experts attended a meeting of the National Commission for the Forecast and Prevention of Major Risks, held on 31 March 2009 to evaluate the threat posed by a series of small and medium-sized tremors that had been shaking L'Aquila for several months. The meeting took place 6 days before the fatal quake struck, and in 2012, Judge Marco Billi ruled that the commission members carried out a "superficial, approximate and generic" risk analysis, and that they made a number of reassuring statements that led 29 of the quake's 309 victims to remain indoors at the time of the disaster, despite the occurrence of two moderate tremors several hours beforehand.

In their verdict today, a panel of three judges headed by Fabrizia Francabandera told the court that only in De Bernardinis's case could a link be proven between the expert's words and the actions of some of the victims.

Speaking immediately after the verdict, De Bernardinis said he could face "God and men" with a clear conscience—although he previously declared that had he been a father of one of the victims, he, too, would have sought justice. "I am relieved but I can't say I'm happy. I am embittered but relieved," said volcanologist Franco Barberi, who at the time of the meeting was the commission’s vice president, about his acquittal. His lawyer, Francesco Petrelli, described the verdict as "inevitable," adding that the original sentence was "visibly wrong in the facts and in law."

Others in the packed courtroom, including some of the relatives of the quake victims, reacted angrily. Angelo Colagrande, representing bereaved surgeon Vincenzo Vittorini, said he was certain that the court acted in "good faith," but that there existed proof of the experts' guilt. "Today we have an earthquake after the earthquake," he said.

Billi's original verdict generated controversy the world over and led many to argue that science itself had been found guilty. In explaining his sentence, the judge was at pains to emphasize that he had not convicted the experts for having failed to predict the earthquake—something, he said, that is beyond the powers of current science—but rather for having failed to carry out their legally binding duties as "public officials." He said that the experts had not analyzed a series of factors indicating a heightened seismic risk, including the fact that previous quakes to have destroyed the town were accompanied by smaller tremors, as well as the nature of the ongoing swarm itself.

In their appeals, the lawyers of the convicted experts objected to the sentence on multiple grounds, taking aim at both the alleged negligence of their clients and the existence of a "causal link" between the experts' statements and people's decision to stay indoors on the fateful night.

One aspect of the ruling that came under particular fire was the notion that the earlier, smaller tremors were a good thing because they discharged energy—an idea that many trial witnesses said led their relatives to remain indoors, but which many scientists regard as incorrect.

The defense lawyers claim that this idea could not have been endorsed by the commission as a whole, as Billi argues, because it was stated publicly only by De Bernardinis, in an interview carried out ahead of the commission's meeting. "It wasn't the commission that reassured; no one said, 'Stay at home because there is a discharge of energy,' " said Marcello Melandri, the representative of Enzo Boschi, former head of Italy's National Institute of Geophysics and Volcanology, to the court. "I challenge anyone to find a word in the minutes of the meeting that are not exactly the opposite of a reassurance."

What's more, Petrelli said, it was not the experts' responsibility to communicate with the public. That was the job of De Bernardinis and two other civil protection officials present at the meeting, he argued: L'Aquila's mayor, Massimo Cialente, and Daniela Stati, then a regional councilor.

In his response to the defense, prosecutor Romolo Como had railed against what he described as a "discharge of responsibility," telling the court that the convicted scientists weren't "four mates in a bar" but "an official commission." He pointed out that during the meeting Barberi had asked the other experts what they thought of the energy-discharge idea, but that none of them replied. "Why didn't anyone object to this?" Como demanded.

Earlier on in the appeal trial, Como also spoke in support of former laboratory technician Giampaolo Giuliani, who claims to have predicted the 2009 earthquake by monitoring emissions of radon gas and whose alarming statements prompted the then–civil protection boss, Guido Bertolaso, to convene the 31 March meeting. Giuliani was "no charlatan," Como said.

Wania Della Vigna, who represents relatives of several students killed in the earthquake, said she will challenge the latest ruling in the Court of Cassation in Rome, Italy's highest appeal court. In the meantime, Como must decide whether to press ahead with a parallel manslaughter investigation against Bertolaso, who allegedly orchestrated the experts' presumed reassurances. The main prosecutor in the original trial, Fabio Picuti, twice requested that this separate investigation be shelved, but his request was contested by lawyers of some of the plaintiffs.