On 6 April 2009, an earthquake struck the Italian town of L'Aquila, a medieval settlement built on an ancient lake nestled in the Apennines. More than 300 people died, and 20,000 buildings were destroyed. This much is clear, but much of the rest of the story lies buried in an avalanche of distortion and misinformation.

It began with Giampaolo Giuliani, a lab technician and would-be earthquake predictor. Tremors had been occurring in the region since January, but Giuliani used his own system – a discredited approach based on measuring radon gas released by stressed rock – to predict a major earthquake on 29 March. Groups toured the area with megaphones warning residents to leave their homes, causing considerable panic, but no quake materialised.

Two days later, the major risks committee, an expert panel that advises local authorities on risks of natural disasters, met in L'Aquila at the request of the Civil Protection Agency to discuss whether a major earthquake was imminent. The meeting was unusually quick, and had apparently been convened in part to reassure the public in the wake of Guiliani's bogus claims. According to Nature, the minutes show that "at no point did any of the scientists say that there was 'no danger' of a big quake", and volcanologist Franco Barberi gave the following, accurate summary: "There is no reason to believe that a swarm of minor events is a sure predictor of a major shock."

After the meeting, Bernardo De Bernardinis from the Civil Protection Agency walked out and addressed the press: "The scientific community tells me there is no danger because there is an ongoing discharge of energy," he told them. "The situation looks favourable." This was not accurate at all. It was 31 March 2009. Six days later, the earthquake struck. A year later, De Bernardinis and six scientists from the committee were indicted for manslaughter.

The nature of these charges has been relentlessly misrepresented by the media, with Nature's superb reporting a notable exception. Fox News claimed: "Italian Seismologists Charged With Manslaughter for Not Predicting 2009 Quake" when the prosecution was announced, and the ABC's headline echoed that statement: "Scientists Convicted of Manslaughter for Failing to Predict Italian Quake". Those headlines – and far too many like them – are simply untrue.

The prosecutors, and the devastated families they represent, are well aware that scientists cannot predict earthquakes. The accusation they make is not that experts failed to predict the earthquake, but that they failed to properly assess and communicate the risks, telling residents they were safe without any scientific basis for doing so. The scientists involved say that the responsibility for this lies with De Bernardinis, who made the now infamous "no danger" statement. De Bernardinis claims that he made his statement in good faith, based on the advice he received. The prosecutor argues that regardless of who made the statement, the scientists on the committee are responsible for failing to come out and correct it.

The seven were found guilty and sentenced to an incredible six years in prison, more than even the prosecutor had requested. Under Italian law the judge's reasoning may not be made public for up to three months, but the impact on the scientific and risk assessment communities is likely to be more immediate. Few scientists will want to take responsibility for similar statements in the future, and those who do are likely to be biased toward crying wolf rather than facing the threat of possible prosecution if their assessments are in error.

The story is a familiar one – politicians, experts and the media coming together in an unholy mixture of miscommunication and misinformation – but the consequences are highly unusual. The scientists involved screwed up, but to prosecute people who communicate risk wrongly while acting in good faith seems excessive, and raises another question: if scientists, why not others? Why not prosecute Giuliani for his false predictions? Can we sue Michael Fish over the hurricane? Can we sue the Daily Mail for misleading the public over climate change?

The Italian prosecution is ludicrous, but no more so than the suing of people like Dr Peter Wilmshurst under Britain's libel laws. In both cases, the same principle needs to be protected: good science is built on open debate, and if seismologists can't express their opinions for fear of ending up in a court room, then many more lives could be put at risk in the future.

• This article was amended on 23 October at 14:03. It originally referred to Dr Peter Wilmshurst being prosecuted, rather than sued. This has now been corrected