Thomas H. Jordan, a professor at the University of Southern California, led a commission that after the disaster advised the Italian government about better ways to communicate earthquake risks to the public. He described the verdicts as incredible, “given that they have just convicted scientists for basically doing their job during a time of crisis.”

“I’m afraid it’s going to teach scientists to keep their mouths shut,” he added.

Scientists said the case raised the issue of when a public warning is appropriate. While predicting the exact time and location of an earthquake is not possible, seismologists are increasingly able to forecast the likelihood that a quake might occur in a certain area within a certain time. But if the likelihood is very low — as it was in this case, despite the increased seismic activity in the weeks before — a warning may do more harm than good. Lawyers for the defendants were unanimous on Monday in their condemnation of the sentence, which exceeded the prosecution’s request of four years in prison, and vowed to appeal.

“I wasn’t expecting this,” said Alfredo Biondi, a defense lawyer. He described the ruling as one of the most erroneous that he had encountered in his long career.

“This was a trial that should not have been held in L’Aquila” because the emotional impact of the quake is still felt so strongly in the city, said Filippo Dinacci, who represents two of the defendants.