MUNICH — Online witch-hunt or smart investigative technique? When Hannover police started a pilot project in March 2011 to ask the public to search on Facebook for offenders, privacy advocates were shocked. At the time, most of the criticism of the project was reserved for the fact that user's data was stored on American servers, which the police did not have access to.

As criticism subsided, the project was eventually extended to the whole country. For regional police spokesman Frank Federau, this is a success story. "We are able to reach young people with our work on social networks," he says. "Feedback comes in quickly and contributes to the success of investigations."

Federau admits that concrete numbers about how successful these sorts of public searches really are don't exist. But then again, if there's an interesting hint or tip, it doesn't really matter how, where and when someone found it. Social network searches have become routine for the police, just like scanning newspapers or listening to the radio.

Germany's Federal Criminal Police Office, too, has been using Facebook more often, moving away from static investigations and towards greater interactivity. The first success: the search for hooligans during the European Soccer Championship in Lille, during which six suspects were identified through Facebook.

"There are strict rules concerning photographic searches," explains Thomas Baumann, spokesman for the Munich police department. The method may not be used unless all other search methods have been exhausted. In addition, the police must first get the permission of the public prosecutor's office. Only once a judge approves it, a suspect's photo can be published.

That's exactly what happened in the case of Jasmin, a young woman who was raped 11 years ago. The crime remains unsolved, and the culprit is probably still out there. The investigation files are at the public prosecutor's office in the central German city of Kassel, sitting in a pile of other unsolved cases.

Jasmin couldn't accept that, so years after the crime, she decided to create a Facebook group called "Search For Unknown Rapist," which already has more than 30,000 members. The group's profile picture features the culprit's identy kit, as well as photos of objects he lost at the crime scene.

All of this could already be found on the police website in 2005. With her Facebook group, however, Jasmin effectively widened the search perimeter. "It's just like distributing digital flyers with material that has been released by the authorities," she says. "It's simply a reminder of an ongoing search."

In fact, the redistribution of the material falls into a kind of legal gray area, says lawyer Udo Vetter. But Jasmin's operation is certainly not a crime in and of itself.

Lynching risks

"The biggest risk she's taking is that the culprit may sue her for invading his privacy," says Vetter. But that remains strictly hypothetical, and the victim will most likely not care, if ultimately her offender is caught.

Before Jasmin launched her Facebook page, she made sure to learn about all the various legal constraints, and she makes it explicitly clear that she will not tolerate "insults, allegations, hostilities or calls for lynching, nor the publishing of individuals' data." Clues should not be posted to the group's page either, but submitted directly to the police.

Prosecuting authorities point out that the offender's identy kit picture, which was produced immediately after the attack, is now out-of-date and may lead to false allegations. Nevertheless, they express sympathy for Jasmin, who in turn is personally empowered by her initiative.

Yet anyone attempting an independent online photo search should be aware that "in Germany, the presumption of innocence prevails, and therefore calls for private searches are strictly forbidden," says Karsten Gulden, an expert in media law. This also applies to insults and death threats the victim might have received, by email for instance: They may not be published with the offending person's profile picture or real name.

"The law says that no one's picture can be circulated without his consent," says Gulden, with exceptions made for images of public figures or those on police fliers. Violation of the law can lead to fines or imprisonment.

But there's more: "If the person who's diffusing the photo knows that the suspect is not guilty, then it may be considered defamation," Gulden notes. If the person was simply mistaken when making the allegations, he or she might still be convicted for slander, which also entails punishment.

Many calls for private searches for individuals later prove to be false, and then not only may the people who started them be held responsible, but also anyone who shared the published information. In the hours after the Boston Marathon bombing, the name and photograph of a missing person was circulated on a "Find Boston Bombers" section of the social media Reddit. It turned out the person, who had nothing to do with the attack, had committed suicide.

"If you're a victim of a crime, you're better off talking to the police," says Gulden. "You may suggest (to the police) to use social media for their search."