On 12 January, in the late hours of the evening, Santiago Lyon (@slyon66), director of photography for Associated Press, was on Twitter. A few hours before, a magnitude 7.0 earthquake hit Haiti, killing more than 200,000 people. At 11.32pm, Lyon sent a message to Daniel Morel. The man, based in Haiti, had just posted on Twitpic an image of the earthquake's aftermath. Lyon's message went straight to the point: "Santiago Lyon of the AP here. Great work so far in a difficult situation. Any chance we can do a deal for your images? Can I contact you? Would like to chat if possible."

With the rise of social sharing sites such as Twitter, Facebook, Flickr and You Tube, it has become increasingly easy for anyone to post images and videos of everyday happenings and, in the case of the Iran election protests and the Haiti earthquake, of newsworthy events.

However, there is an inherent risk with such images. On 14 January, Libération dedicated several pages to Haiti. Among the photographs the French newspaper used, one stood out. It featured a team of orange-clad rescuers searching the ruins of a tall building. Two problems quickly emerged: the few rescuers there weren't wearing orange jumpsuits, and no such buildings existed in Haiti. The image, instead, depicted the search and rescue efforts following the 2008 Chinese earthquake.

Four news agencies - Agence France Presse, Sipa, Max PPP and Chine Nouvelle - distributed the wrong image in the hours following the earthquake. Each time, it was credited with "Haiti, 12 January 2010". According to Chine Nouvelle, the image came from Radio Tele Ginen, a Haitian radio station which sourced it from the social networking site Twitter.

Searching social networks for "eyewitness content" has become standard procedure for news organisations, says Lyon. However, they must have systems in place to authenticate the images. At AP, "we assess each photo on a case-by-case basis, only selecting the images that we feel are coherent and newsworthy and actually show the events they purport to show."

Then follows the difficult task of identifying the copyright owner. "We search for contact information, we call, email, or comment on the photo asking the person to get in touch with us."

Reuters uses the same procedures, Thomas Szlukovenyi, global editor of pictures, tells BJP. "We occasionally use pictures from social networking websites on major breaking news stories, but they go through an extensive verification and editorial evaluation process before we commit to using them and proceed with the photographer's payment," he says. "Haiti was a good example as we were not comfortable using the very early pictures available on social websites. Since we could not reach the people who posted the image, we did not use them. Our team of photographers was shortly in place and we were able to show the world ourselves."

Once an image has been authenticated, it is distributed to the wire's subscribers and members. "We try to credit using this phrasing: 'In this image provided by Person's Name (we add the occupation if we know it)'," says Lyon. "We don't credit images just to social media. We try to identify an individual who provided the image and always try to get permission from that individual to use the image."

However, even the best procedures aren't infallible. "In the rare event of an inaccuracy on our end," says Szlukovenyi, "we follow a strict editorial process and issue an immediate correction as soon as we find out about it. There is a very short window of opportunity to use pictures from social websites as they are cross-posted in minutes and verification becomes even more difficult."

AP calls this type of correction "photo elimination", says Lyon. "The notice goes out to all of our subscribers, alerting them that the image should be withdrawn."

Citizen journalists
When your entire business relies on eyewitness accounts and street photography, these safeguards are essential. Citizenside, which launched in 2006, distributes still and moving images from thousands of "citizen" contributors around the world. "Journalists believe social networks and citizen contributions are a nightmare," associate director Matthieu Stefani tells BJP. "In fact, it can be a big opportunity."

Citizenside has put in place a robust set of processes to ensure the authenticity of its content. Similarly to AP and Reuters, it constantly checks the identity of its contributors. "Who sent it? What did he send us before? Can we trust him? This works like the Power Seller system on Ebay. We also look at where the images were sent from, and analyse the metadata through a series of software." For example, one program allows Citizenside to find out if an image's pixels have been modified.

However, Stefani says, the best tools journalists can use are the ones they apply to their work every single day. "You pick up your phone and call people. If we receive an image of a bank robbery, we'll call the police or even the bartender of the pub down the road. We'll ask him: 'Did this happen in your street?' It's simple. It's basic journalism."

Ultimately, "fake" images will find their way into circulation, "but they are really rare", says Stefani. And, more often than not, the race for breaking news stories is to blame for what slips through the net.