On September 21, 2011 we reported on the lawsuit against scientists who provided earthquake forecasts to the Italian government. The lawsuit arose after the deadly earthquake in L'Aquila in April 2009. On October 22, 2012, the seven forecasters were sentenced to 6 years in jail and have been ordered to pay $10.2 million in damages. The verdict is unusual over the past century in free societies. Based on the reports we have seen, there was no claim that there was intent to harm, nor are we aware that evidence was presented that the scientists failed to use proper procedures. It is extremely difficult to predict the timing of earthquakes, so "bad forecasts" are common. Until this matter is resolved, we advise experts to avoid making forecasts of natural disasters in Italy.

When forecasting outside of Italy, we advise forecasters to use evidence-based principles of forecasting. For example, forecasters should provide evidence-based information on uncertainty. Failing to use evidence-based principles seems to be the only sound basis to challenge bad forecasts—other than intent to deceive, which sometimes occurs in financial markets. Consider the field of medicine: Doctors are often successful sued when they fail to use evidence-based procedures. For forecasting, we refer readers to "Standards and Practices for Forecasting". As far as we are aware, it is the only published list of evidence-based principles of forecasting. It contains a short review of law cases involving faulty forecasts in the last section.

Scott Armstrong and Kesten Green