A spate of "sexting" cases in the US has prompted calls for a change in the law. But what is "sexting" and why has it left parents and prosecutors alike wondering how to tackle it? The BBC's Penny Spiller reports.
One in five US teenagers admit to sexting
It may seem like harmless fun to a 15-year-old wanting to impress their new boyfriend or girlfriend.
But the practice of sexting - sending nude or semi-nude images of oneself to others via mobile phones - is having unintended and, in some cases, tragic consequences.
The risk of having one's private pictures distributed among schoolmates or uploaded on to social-networking websites is only one part of it.
It could also lead to a criminal conviction as a sex offender for any teenager who forwards them on to someone else.
Sending or distributing explicit photos of a child under 18 is, in many countries, illegal. It is also illegal to send such photos to a minor - even if both parties consent to it.
A spate of cases in the United States has seen several "sexting" teenagers arrested on charges of child pornography - alarming parents, school officials, police and prosecutors.
It has led people to ask whether threatening children with the same law that was drawn up to protect them - and potentially creating many more sex offenders - is the best way to tackle the phenomenon of "sexting"?
One such case has ended up in a court in Pennsylvania and is being closely watched by interested groups across the US.
The route to the courthouse began when several pictures of pupils in various states of undress were discovered on other pupils' phones by staff at the local school in Tunkhannock.
The phones were handed to Wyoming County district attorney George Skumanick, who decided to act.
He had been particularly alarmed by the case of Jessica Logan, an 18-year-old from Ohio who took her own life after pictures she sent of herself to her boyfriend ended up in the hands of fellow pupils.
Mr Skumanick offered the Tunkhannock pupils in question, around 20 of them, a six-month education programme to learn more about the consequences of their actions - and to help them avoid a child pornography charge.
Three girls - and their parents - refused to sign up, and are now suing Mr Skumanick with the help of the American Civil Liberties Union (ACLU).
Mr Skumanick said he thought he was being "innovative and progressive" when he offered the youngsters the classes.
"I didn't have to give them this opportunity. I could have just charged them," he told the BBC.
He says the recent arrest of a man in Georgia for allegedly making internet contact with one of the pupils involved in the case justifies his concern. The man has been charged with criminal solicitation and corruption of minors.
"Our main goal was simply for the pupils to go through the programme we had developed to help them learn about the dangers of sexting," Mr Skumanick said.
But Witold Walczak, legal director for ACLU in Pennsylvania who is fighting the case on behalf of the pupils, said the district attorney's actions risk setting a dangerous precedent.
"Child porn is about the abuse and exploitation of minors by adults. That's not happening here," he said.
"The kids who do this are doing potential harm to themselves. They are both the perpetrator and the victim. Why would you want to compound that with a criminal prosecution and conviction?"
This is one of at least 20 prosecutions that have been undertaken or threatened in a number of US states in recent months.
Jessica Logan, says her mother, was a "vivacious, fun" 18-year-old.
But her life changed when a nude photo of herself she sent to her boyfriend ended up in the hands of hundreds of teenagers in her home city of Cincinnati, Ohio.
For months, she faced taunts of "slut", "porn queen" and "whore". Insults were posted on her MySpace and Facebook pages.
She became introverted and skipped classes, her friends say.
Despite this, Jessica went on local TV - her identity concealed - to "make sure no-one else will have to go through this."
A few months later, in June 2008, she hanged herself in her bedroom.
Her devastated parents, Cynthia and Albert Logan, are now campaigning for greater awareness of the dangers of sexting.
But it is not just an American problem. Cases have also been reported in Great Britain, New Zealand and Australia.
The New South Wales state government in Australia launched an education campaign this month after receiving reports that girls as young as 13 were sexting.
"I urge parents to warn their children about the consequences of sexting," state Community Services Minister Linda Burney said.
"It may be a difficult conversation but I think every parent will agree it is a very important one."
A survey of more than 1,000 teenagers in the US last year found that around one in five 13 to 19 year olds had sent nude or semi-nude pictures of themselves either by text or online.
A third of boys and a quarter of girls said they had had nude or semi-nude images, originally meant to be private, shared with them, the National Campaign to Prevent Teen and Unplanned Pregnancies found.
Bill Albert of the Washington-based organisation says today's generation of teenagers needs to find a line between public and private behaviour in light of the new technology.
"The line is very much more blurred than in the past. The technology is so new that people haven't found their moral compass when using it," he told the BBC.
"The problem is that even if you think you are sending a picture only to your boyfriend or girlfriend of the moment, it can go from private to global in a nano-second.
"And something like that can stick with you, almost like a cyber-tattoo, for the rest of your life."
Mr Albert said that while child porn laws are "an awfully severe and blunt instrument", alerting teenagers to the legal consequences of their actions is no bad thing.
"The teenagers in our survey were very surprised by the legal action taking place," he said. "The legal consequences were very low on their list of concerns."
Parry Aftab, a leading authority on cybercrime, is campaigning for a change in the law in the US.
She says the current legal options for dealing with cases of sexting "are insane".
She wants to see children facing a misdemeanour charge rather than child pornography - a much less serious offence that would eliminate the possibility of a teenage offender being labelled a sex offender for years.
A number of states in the US are considering this approach.
Vermont has introduced a bill that would legalise the consensual exchange of graphic images between two 13-to-18-year-olds, although passing on such images would remain a crime.
Ohio is considering a proposal that would see the practice of sexting reduced from a felony crime to a misdemeanour. Mr Skumanick would like Pennsylvania to consider something similar.
However, ensuring laws are available so that prosecutors and police can still act over sexting are vital, Ms Aftab says.
"It is dangerous behaviour that we don't want children to be encouraged to do," she told the BBC.
"Not only could these images end up in the hands of paedophile groups and place kids at higher risk of being targeted, but they could also be subject to extortion by those who have ended up with the images."