For more than two years British accountant Paul Chambers has been embroiled in a complex legal battle regarding a tweet he posted in January 2010:

“Crap! Robin Hood airport is closed. You’ve got a week and a bit to get your shit together otherwise I’m blowing the airport sky high!!”

Despite airport management believing the tweet to be ‘not credible’ as a threat, the police were contacted anyway, and thus began a landmark case – the so-called Twitter Joke Trial – that has put free speech and social media under enormous scrutiny.

Two High Court appeals later, and Chambers has been cleared of “sending a public electronic message that was grossly offensive or of an indecent, obscene or menacing character contrary to the Communications Act 2003”, but questions have remained about what is, and what is not, acceptable in the social sphere.

Today, director of public prosecutions Keir Starmer has issued guidelines for the prosecution of people who misuse social media, in a bid to clear the murky waters surrounding this controversial area.

According to the guidance, users that retract offensive comments, by swiftly deleing them and showing remorse, will be less likely to face prosecution.

“If a message is taken down very swiftly and there is remorse then it may not be proportionate to have a criminal prosecution,” said Starmer. “It is not a defence that you have sobered up but it is relevant that whatever the material was, it was taken down pretty quickly when the person realised it was inappropriate.”

The 14-page report draws a clear distinction between “grossly offensive, obscene or false posts” and those that “credibly threaten violence, harass or stalk and breach court orders”. The Crown Prosecuting Service (CPS) intends to deal “robustly” with charges of the latter, which will include trolling.

There are measures in place to ensure that the CPS will not be swamped by increased volumes of allegations involving social media posts (it’s dealt with around 60 in the last 18 months). “There is a high threshold that must be met before criminal proceedings are brought and in many cases a prosecution is unlikely to be in the public interest,” said Starmer, indicating that a post worthy of prosecution must be shown to be more than offensive, shocking, disturbing, satirical or rude, or more than the expression of unpopular or unfashionable opinions.

Paul Chambers’ solicitor David Allen Green called the new guidelines a “step forward”, adding that “the real test will be in practice, especially the thresholds adopted by the police when making arrest decisions”.