Scientists must not be muzzled

Academic freedom does not extend to challenging the motivations of other researchers, only to the truth or otherwise of their statements. This is similar to the way that the freedom of the press does not extend, for example, to invasions of personal privacy.

But in any case, the courts should not be the arbiters in disputes over the validity of claims for demonstrated or hypothesised scientific evidence. The peer review process, despite its many shortcomings, is still the best mechanism we have for making judgments about scientific advances and differences.

Legal action should not be used to prevent a scientist from making public statements based on expert opinion, however strongly expressed - or however contentious the topic.

Bringing laws to heel

It is appropriate that this issue is being taken up by national science academies (as in the case in Peru). But concern should extend beyond the scientific community. All countries should examine their defamation laws and assess whether they may discourage informed debate on key issues of social concern.

For example, Britain's new coalition government has promised to consider legal changes that would better protect individuals such as Singh and allow them to play a robust part in key debates, without the fear that an ambiguous phrase could lead to personal bankruptcy, or even a prison sentence.

Other countries currently empowered - as Peru apparently is - to act against scientists should consider whether it is in the public interest to do so. The recent threat by the Indian government to imprison researchers warning against the dangers of genetically modified crops is a case in point (see Mutual respect in the GM crop debate).

Scientists have a responsibility to speak out about topics on which they hold expert knowledge, particularly if this knowledge can better inform a political debate. But society, in turn, has a responsibility to protect scientists when they do.