A spray of DNA to keep the robbers away

When the McDonald's down from City Hall here was burglarized a few years ago, its managers decided they needed a new security system.

It was just about that time that local police officers were offering something totally different that they hoped would stem a rising tide of robberies that occur mainly in the immigrant neighborhoods of this rough-and-tumble port city. The new system involved an employee-activated device that sprays a fine, barely visible mist laced with synthetic DNA to cover anyone in its path, including criminals, and simultaneously alerts the police to a crime in progress.

The mist -- visible only under ultraviolet light -- carries DNA markers particular to the location, enabling the police to match the burglar with the place burgled. Now, a sign on the front door of the McDonald's prominently warns potential thieves of the spray's presence: "You Steal, You're Marked."

The police acknowledge that they have yet to make an arrest based on the DNA mist, which was developed in Britain by two brothers, one a policeman and the other a chemist. But they credit its presence -- and signs posted prominently warning of its use -- for what they call a precipitous decline in crime rates (though they could not provide actual figures to back that up).

But the goal is not so much capturing crooks as scaring them away. "The whole thing is prevention, not about recovering stolen goods or capturing criminals," said Donald van der Laan, whose company, the Rhine Group, distributes the spray. As far as the DNA is concerned, "the material is identical" to human DNA, he said, "though there is a different sequence of components." Much of the spray's effectiveness, he said, comes from the mystique surrounding DNA.