Six Italian scientists and a government official have been found guilty of multiple manslaughter for underestimating the risks of a killer earthquake in L'Aquila in 2009.
They were sentenced to six years in jail on Monday in a watershed ruling in a case that has provoked outrage in the international science community.
The experts were also ordered to pay more than nine million euros ($A11.5 million) in damages to survivors and inhabitants. Under the Italian justice system, the seven will remain free men until they have exhausted two chances to appeal the verdict.
Some commentators had warned that any convictions would dissuade other experts from sharing their expertise for fear of legal retribution.
Prosecutor Fabio Picuti had asked for jail sentences of four years for each defendant for failing to alert the population of the walled medieval town of L'Aquila to the risks, days before the 6.3-magnitude quake killed 309 people.
All seven were members of the Major Risks Committee, which met in the central Italian town on March 31, 2009 - six days before the quake devastated the region, tearing down houses and churches and leaving thousands homeless.
'This is a historic sentence, above all for the victims,' said lawyer Wania della Vigna, who represents 11 plaintiffs, including the family of an Israeli student who died when a student residence collapsed on top of him.
'It also marks a step forward for the justice system and I hope it will lead to change, not only in Italy but across the world,' she said.
The bright blue, classroom-sized temporary tribunal in L'Aquila - built on an industrial estate after the town's historic court was flattened in the quake - was packed with lawyers, advisers and international media for the verdict.
Four of the defendants were in court, as well as a small group of survivors.
Aldo Scimia, whose mother was killed, teared up as the verdict was read out.
'We cannot call this a victory. It's a tragedy, whatever way you look at it, it won't bring our loved ones back,' he said.
'I continue to call this a massacre at the hand of the state, but at least now we hope that our children may live safer lives,' he added.
Prosecutor Picuti had slammed the experts for providing 'an incomplete, inept, unsuitable and criminally mistaken' analysis, which reassured locals and led many to stay indoors when the first tremors hit.
The government committee met after a series of small tremors in the preceding weeks had sown panic among local inhabitants - particularly after a resident began making worrying unofficial earthquake predictions.
Italy's top seismologists were called to evaluate the situation and the then-vice-director of the Civil Protection agency, Bernardo De Bernardinis, gave media interviews saying the seismic activity in L'Aquila posed 'no danger'.
'The scientific community continues to assure me that, to the contrary, it's a favourable situation because of the continuous discharge of energy,' he said.
Government lawyer Carlo Sica, who had called for the seven defendants to be acquitted, said that minutes from the March 31 meeting were not valid as evidence because they were only written up after the April 6 earthquake.
'They are not guilty of anything, the earthquake's no one's fault,' he said.
Filippo Dinacci, lawyer for Mauro Dolce and Bernardinis, had criticised the charges last week as something out of 'medieval criminal law'.
'The ruling in my opinion is not fair. We will certainly be appealing,' said Alessandra Stefano, lawyer for expert Gian Michele Calvi, after the verdict.
The case sparked outrage in the international scientific community when the charges were brought against the geophysicists in 2010, with many complaining that they were merely scapegoats and warning against putting science on trial.
More than 5000 members of the scientific community sent an open letter to President Giorgio Napolitano denouncing the trial against colleagues for failing to predict a quake - a feat widely acknowledged to be impossible.
The seven include Enzo Boschi, who at the time was the head of Italy's national geophysics institute; Giulio Selvaggi, head of the INGV's national earthquake centre in Rome; and Franco Barberi from Rome's University Three.
The other scientists found guilty are Mauro Dolce, head of the Civil Protection's seismic risk office; Gian Michele Calvi, head of the European centre of earthquake engineering; and Claudio Eva from the University of Genoa.