Oct 23 2012

Guilty Verdict for Italian Earthquake Scientists

This news is plastered over every general and science news outlet I can find – Italian scientists have been found guilty of manslaughter for failure to properly warn about the 2009 L’Aquila earthquake. They have been sentenced to 6 years in prison and ordered to pay $12 million in damages.  They have two appeals left, and can remain out of prison until they exhaust their appeals.

It is easy to be outraged at a decision that seems so ridiculous on its face. I always try to find the most charitable interpretation of each side of an argument, and so I searched through the news reports for a cogent explanation of this decision. First, it seems the scientists were not convicted for failure to predict the quake, but for how they communicated to the public about the risk of the quake occurring. I could not find a full exact quote of what they did say. The two partial quotes I could find indicate that they said the small tremors that preceded the 6.3 magnitude quake that killed 309 people were “unlikely” to be followed by a large quake. Further, they indicated that small tremors may actually decrease the risk of a larger quake by dissipating energy.

The guilty decision seems to hinge on the fact that many residents were afraid that a large quake was coming and would have evacuated, but were reassured by the risk commission’s statements and decided to stay, leading to their death.

The relevant science seems pretty clear. Low level seismic activity rarely is followed by a large earthquake, and most large earthquakes are not preceded by such minor tremors. Therefore the predictive value of the preceding tremors was very low. It was therefore entirely accurate for the scientists to say that the risk of a large quake was “unlikely.” If one makes a statement of probability, and the low level probability outcome occurs, that does not make one wrong.

This concept comes up in medicine all the time.  Physicians come up with a “differential diagnosis” – a list of possible diagnoses in order of likelihood. A physician may act on the diagnosis that is 95% likely to be true, but for 1 patient in  20 the 95% diagnosis will be wrong. That does not mean the differential diagnosis was wrong. Sometimes, even, a patient turns out to have a rare disease. Saying that the diagnosis is unlikely prior to the diagnosis being made would not be wrong.

The scientific community also agree that the state of the science is such that earthquakes are “inherently unpredictable.” So the scientists could not have predicted the quake, and they were correct when they said it was unlikely. We can further ask – was their assessment within the scientific standard for their community. Well, a letter from the American Association for the Advancement of Science (AAAS), signs by 5,000 scientists, including many geologists, argued that it was. The letter to president Giorgio Napolitano said, “To expect more of science at this time is unreasonable.”

Of course the scientific community is warning about the “chilling effect” this will have on science and the communication of certain sciences to the public. At the very least, if this verdict stands Italy might find it difficult to find geologists to work on any risk commissions, or offer any kind of information or analysis to the public. The liability would be too great. It might also motivate scientists to overestimate future risks in order to cover themselves. In medicine the fear of lawsuit arguably leads to the over-ordering of tests. In geology it may lead to needless fears about the risks of impending quakes, causing panic and far more harm than it prevents.

The guilty decision, in other words, may be far more reckless than the court is accusing the scientists of being.

It does seem that this episode exposes a failure to properly communicate science to the public, and I’m not just talking about this one incident. Sure, in hindsight the Italian geologists could have put their information into a more thorough context and explained the nature of predictions and risk (although it’s not clear this would have made any difference). Having a more scientifically literate public would also help. Of course I think every press conference about a science topic is and should be a teaching moment, it’s not realistic to expect these scientists to make up for a lack luster public science education in one brief news report.

This story is not quite over yet, as the scientists have two appeals left. It is possible that the backlash of worldwide ridicule and condemnation will have some effect and the guilty verdict will not stand. We can hope.

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