Six Italian scientists and one government official are facing four years in prison for allegedly downplaying the severity of the risk of an earthquake in L'Aquila, Italy, in 2009. (Photo: Flickr.com/martinluff)

Six Italian scientists and one government official are facing four years in prison for allegedly downplaying the severity of the risk of an earthquake in L'Aquila, Italy, in 2009.

The seven are being tried for manslaughter after downplaying the likelihood that a series of tremors in early 2009 were a precursor to a much larger earthquake. Later that year, the city was hit by a magnitude 6.3 earthquake that killed 309.

During the prosecution's closing arguments, the prosecutors said the scientists and the official gave inadequate and deceptive information to the public. At a meeting on March 31, 2009, a week before the large earthquake hit, the scientists said the a large quake was "unlikely," but cautioned that they could not be certain.

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"I think that what people don't understand is just how low the risk was. These swarms of earthquakes do happen all the time," John Vidale, a seismologist at the University of Washington, told LiveScience. "We have swarms in my state, Washington, all the time, and I'm not sure of a single one that's ended with a large earthquake."

In 1988, researchers found that half of large earthquakes were preceded by foreshocks. But swarms of smaller earthquakes are unreliable predictors of earthquakes, experts say, with only 2 percent of small quakes leading to a larger one.  Experts said making their failure to predict the earthquake a crime is a slippery slope.

"Our ability to predict earthquake hazards is, frankly, lousy," Seth Stein, a professor of Earth sciences at Northwestern University in Illinois, told LiveScience. "Criminalizing something would only make sense if we really knew how to do this and someone did it wrong."

The trial is currently on hold until October 9, when the defense will present its closing arguments.