L'Aquila ruling: Should scientists stop giving advice?

This week six scientists and one government official were sentenced to six years in prison for manslaughter, for making "falsely reassuring" comments before the 2009 L'Aquila earthquake. But was this fair?

First, we have to understand limits of earthquake science. Ian Main, Professor of Seismology and Rock Physics at the University of Edinburgh, was part of an international commission on earthquake forecasting set up after L'Aquila.

He says it is possible to predict where an earthquake might happen at some point. But it is impossible accurately to predict exactly when that earthquake will happen.

"We can forecast that they're almost certain to happen with a very low probability - maybe once in 100, once in 1,000 years depending on the size of an earthquake and in a given zone. And that's a hazard that's there all the time," says Main.

In L'Aquila a series of smaller tremors - a so-called "seismic swarm" - occurred before the larger earthquake eventually struck. Main says that after a seismic swarm the probability of a larger earthquake happening is increased but it is still low.

"There's… a one in 100 chance of a swarm ending in a larger earthquake, or a smaller earthquake triggering a bigger one. It's very rare but it does occur," he says.

In other words, 99 times out of a 100 a series of tremors will not result in a larger earthquake. In L'Aquila, of course, it did happen.

In the past in L'Aquila after a swarm of tremors some residents would leave their houses and sleep in their cars, to avoid the danger of collapsing buildings. However on this occasion comments by the authorities prompted some of those people to change their usual response and stay inside.

This case is not about the scientists' ability to predict earthquakes - it is about their statements communicating the risk of an earthquake.

The Italian seismologists understood that an earthquake was unlikely but not impossible. In a press conference, however, the message seemed to be that that meant there was nothing to worry about at all. This is the falsely reassuring statement which formed part of the case against them.

The government official, Bernardo De Bernardinis - deputy chief of Italy's Civil Protection Department at the time - is reported to have advised worried residents to go home and sip a glass of wine. He even specified what kind: "Absolutely a Montepulciano."

Bernardinis was criticised for saying residents should go home and drink wine
"Communication is at the bottom of this whole case," says David Spiegelhalter, Professor of the Public Understanding of Risk at Cambridge University.

"The scientists met, they did a risk assessment and they concluded there was an increased risk but the absolute risk was very low. They concluded they couldn't be confident there would be an earthquake.

"However this afterwards got communicated and understood by the public as a message that they could be confident there could not be an earthquake… that's what people understood and that's what has led to this court case."

Spiegelhalter accepts that it is the responsibility of scientists to communicate risk effectively. But he fears the L'Aquila case might have damaging consequences. Could it deter scientists from offering their independent advice?