A dirty duffle bag sits on the floor of Marko Moritz's office, full of spray paint cans that clink loudly when he unzips it. Moritz, who is Berlin's top anti-graffiti cop, is bald and broad-shouldered, dressed in jeans, a dark shirt and a light tie. He looks unmistakably like a policeman.
Graffiti artists, he explains, often wear fluorescent orange vests to pass themselves off as railway workers when they go to ''bomb'' – that is paint – a train station. In response, the police have their own disguises, of which the duffle bag and cans are part.
''We go out at night to the train stations, dressed in baseball caps and with these cans,'' he explains. ''We have to fit in ... so we can catch them.''
It's one part of an escalating strategy the police are using to dent Berlin's graffiti juggernaut. With about 15,000 graffiti offences reported last year in Berlin, costing €30 million in damage, Chief Detective Moritz has the unenviable job of trying to stop what seems to be an unstoppable force.
Europe's graffiti ground zero
Berlin is Europe's graffiti “hotspot” right now, Moritz says – a claim few would challenge when seeing vandalism on nearly every single building in town. He estimates there are between 60 and 70 highly active and organized homegrown ''crews'' operating here and many more part-timers and visiting sprayers who see the city as the place to make a name for themselves.
While many Berliners seem to accept graffiti as a fact of life in Europe's poor but sexy creative capital, it is a crime that the police say they take seriously.
Moritz is in charge of the Graffiti in Berlin squad, which has 36 officers drawn from both the Berlin and federal forces and is based in a large police complex in Lankwitz, in the southwestern suburbs. Much of the squad's time is spent gathering intelligence on the major crews and sprayers. To get this, they go undercover to graffiti festivals, gather tip-offs – including coaxing information from sprayers they've caught – and sift through graffiti chat rooms on the internet.
They are helped by the fact that graffiti sprayers crave recognition and therefore document and promote their work. A bold attack on a train, for example, is a fleeting achievement since ''bombed'' trains are hauled straight off to the depot and cleaned. The only way to preserve the moment is to film it and post it on a website or print it in a magazine.
Sprayers also keep ''black books,'' or albums of their work, Moritz explains. Once the police have enough evidence to link a tag name to an individual, the squad can apply for a warrant, search their house and seize these black books as evidence.
''This is a very good thing for us,'' Moritz says of sprayers' tendency for self-incrimination. Moritz won't reveal how his unit hacks into private chatrooms or links graffiti tags to real individuals. ''I have my secrets,'' he says with a smile.
What he will proudly reveal is the database of between 7,000 and 8,000 graffiti ''tag'' names, which the squad has been compiling since 1995, the year after it was set up.
''This is our treasure,'' he says. By punching a tag name into the computer, he can bring up every incident where the tag has been used, which crew the sprayer belongs to, who his associates are and any other information the police have on him.
Every sprayer has his own tag, Moritz says. To pinch another man's tag invites trouble. Therefore, if the police can nail a sprayer for one attack, they can argue he is responsible for every other wall bearing his tag.
''We can go to the judge and say, 'This is the rule of the scene,''' he says. ''The tag is individual. If they use someone else's tag, they could be in danger.''
But not all judges buy the argument, according to Peter Brasche, a Kreuzberg lawyer who defends graffiti artists and takes painted canvasses as part of his payment.
Citing the code of the graffiti subculture isn't enough to satisfy the strict definition of legal proof, he says. While acknowledging that some members of the GIB squad really know their stuff, Brasche is critical of the squad's methods. A notorious incident in which the squad took to the skies in a helicopter with night vision glasses earned widespread ridicule. ''Even the people who don't like graffiti laughed at them for that,'' Brasche says.
But Brasche is also critical of what he says are heavy tactics the squad uses to coax information about young sprayers they've caught.
''They are good at scaring people,'' he says.
Either way, the squad gets results, arresting about 1,500 alleged sprayers a year. Sprayers face fines or community service for their first few offences but the penalties can escalate to two years' prison. The GIB squad focuses on the hardcore crews, leaving political graffiti and street art to other sections of the police.
''It takes a long time to learn to read tags. You need some years to understand the rules and the people,'' says Moritz, who has been with the squad since 2000.
Violence on the rise
He fishes out a sprayer's black book the police are holding as evidence. It is full of pictures of the young man and friends posing in front of graffiti pieces. One picture shows the man brandishing an automatic pistol.
''I think probably he's just a show off,'' Moritz says. But it underlines his biggest concern: that the Berlin graffiti scene is becoming more violent, with crews attacking one another in tribal skirmishes.
''Physical violence is a huge problem. At the start, they had the rule of no violence, but in the last few years, it's a completely new part of the graffiti scene.''
One sprayer, whose tag name is Anek, told The Local that a friend of his had been stabbed in the neck by a rival crew. Everyone who knows the scene agrees that violence is on the rise, though it is still a small proportion of crews that are involved in more serious crimes.
Moritz acknowledges Berlin will always have graffiti, though he insists his squad is making a difference. After eight years immersed in the scene, he's also formed his own opinions about what distinguishes the good graffiti from the bad.
''I know my own style is shit,'' he says with a laugh. ''But I think some of these people will have the possibility later in life to make a lot of money.''
Unfortunately, it's not his job to judge, he says. Art, vandalism, talent or trash – as far as he's concerned, it's just a crime.