JEALOUS MISTAKE: The judge allowed Joshua Ashby's photo to be taken, saying there was "a certain symmetry to it''.

A jilted lover has made legal history by being jailed for posting a photograph of his ex-girlfriend naked for millions of Facebook users to see.

After 12 hours, police and Facebook authorities shut down the woman's account but not before it was available to all 500 million active users of the social network.

Joshua Simon Ashby, 20, held a piece of paper over his face yesterday in an attempt to prevent The Dominion Post photographing him as he was being sentenced.

Judge Andrew Becroft, in Wellington District Court, allowed Ashby's photo to be taken, saying "there was a certain symmetry to it", then stepped in to tell Ashby not to hide his face.

Ashby posted the photo in an "irresponsible drunken jealous rage" after the breakup of their five-month relationship, the judge said.

It is believed to be the first time someone has been sentenced for a crime committed using social media under the seldom-used morality and decency section of the Crimes Act.

Ashby's parents, Michael and Lisa, hope the jail term will deter others from the "dark side" of Facebook.

The Island Bay painter was jailed for four months after pleading guilty to a charge of distributing indecent matter and six others of threatening to kill, wilful damage, theft of the woman's clothes, and assault.

He had included in text messages to her on July 23: "I'm going to kill you" and "Dead bitch". He then posted a photograph he had of her naked in front of a mirror to her Facebook page. Initially, 218 of her friends had access to it, but Ashby then made it publicly available and changed her password. Her friends saw the photo and texted her to tell her.

Judge Becroft said he was adapting an old print law for the internet age. "Technology can't be used in this way," he warned. "You would do incalculable damage to someone's reputation."

Mr and Mrs Ashby told The Dominion Post they supported their son fully, but the sentence was "excellent" work by the judge.

"He's not a mean or nasty person," Mr Ashby said. "Because he's intense and puts everything into things, he probably reacts in an intense way when it doesn't go well for him."

Mrs Ashby, who visited her son in prison during his five-week remand, added: "And maybe when someone thinks about doing it they'll remember someone got sent to prison for that and they'll say: `Oh my God, I'm not going to do that.'

"He does feel for his ex-girlfriend and what he's put her through and he just wants to put it behind him."

At the same time as the Facebook incident, Ashby stole two of the woman's dresses, soaked them in water and cut them up. She forgave him and they reunited briefly before a drunken argument in October led to Ashby pushing her to the ground and snapping her cellphone in half.

Judge Becroft told Ashby the victim felt degraded. "She was embarrassed, felt exposed and ridiculed and couldn't sleep after."

Defence lawyer Leah Davison said Ashby knew "full well" he needed to deal with problems around drugs and alcohol and behaving in a "very immature manner" when angry and upset. A painting apprenticeship awaited him when he got out of prison.

Netsafe spokesman Sean Lyons said the most common call the cyber watchdog received from adults was from people after relationship breakups, upset that pictures had been inappropriately used – some on Facebook, but mostly sent by email.