She robs, she injects herself with heroin, she seems to kill with almost professional precision – and, as far as German detectives are concerned, she has no identity.

The hunt for the woman known as the Phantom of Heilbronn has been stepped up after the discovery of new traces of her DNA in a blood-stained white Ford Escort. “The noose is tightening,” Erwin Hetger, the chief of police in Baden-Württemberg, southwest Germany, said.

For 15 years a mysterious woman has been leaving traces of her DNA at crime scenes across Europe, suggesting her involvement in at least six murders and scores of break-ins. Rarely are there witnesses. Instead, police in the countries where she has been roaming – Germany, France and Austria – have had to piece together a profile from saliva left on biscuits nibbled at the site of a murder, a discarded cigarette packet and a spot of blood.

She may flit across borders like a ghost but she has been leaving a trail behind her. A human being loses on average four hairs in an hour and sheds a million dead cells in 40 minutes: that forensic scence harvest is all the police have to go on.

“The woman has left genetic clues in Germany, France and Austria,” Chief Inspector Bruno Bösch, the head of one of three German teams that has been on the case, said. “I have travelled 60,000km (37,300 miles) across Europe, questioning witnesses.”

In Austria there are DNA traces linking the woman to 13 crime scenes. Police arrested two burglars in Linz who must – according to some recovered hairs – have been on a break-in with the woman.

No Identikit portrait, no reliable description, not even a coherent crime profile. Sometimes she pilfers from a shed, then suddenly last year she was in the backseat of a patrol car when a 22-year-old policewoman was killed and her companion was seriously injured in Heilbronn.

“Have I missed something?” one despairing investigator has asked.

In February the bodies of three Georgian car dealers were fished out of a river. The blood of one of them was found in the Ford, as were hairs from the Phantom. The car had been bought by the police last year for an undercover operation so they should be able to reconstruct the movements of the vehicle and perhaps the identity of its passengers. It is a long shot, but the closest that the police have come to tracking down the Phantom since her DNA was first identified seven years ago.

The trail began when a boy trod on a heroin syringe in the sleepy spa town of Gerolstein, Germany. His parents were so worried that they insisted on a full blood analysis. When the DNA traces were fed into a central data bank a match with genetic material left at two unsolved murders was found. The first was of a 63-year-old who was killed in 1993 with the wire used to bind bouquets. The killer had left her DNA on the rim of a floral-print tea cup.

The evidence suggests that the Phantom is an addict – hence the desperate petty burglaries. Flakes of her skin have been found on a bullet in a gun used between feuding Romany chiefs. That suggests the Phantom might be a Gypsy but investigations in the community have not yielded any results. Nor has saliva testing of 800 women in the Heilbronn area.

“It all boils down to this: we do not know what this woman looks like, we just know her genetic code,” Chief Inspector Bösch said.

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