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DNA traces of an unknown woman have been found at crime scenes spanning 16 years. Police admitted on Thursday that they were chasing a phantom killer when swab sticks used for testing were found to be contaminated.
Phantom's DNA surfaced in a high profile Heilbronn murder case
One of Germany's most wanted criminals may not even exist. Investigators who found DNA traces of a mystery woman suspected of committing at least three murders and numerous break-ins over the past 16 years, admitted on Thursday, March 26, they might have been chasing a phantom.
The first DNA trace from the female suspect turned up at the scene of a murder in May 1993. Later her DNA fingerprint matched the 2001 killing of a 61-year-old man and the cold-blooded murder of a 22-year-old policewoman in Heilbronn, a small German town north of Stuttgart two years ago.
The Heilbronn case had led to a police investigation that consumed thousands of man hours, but the trail was as cold as ever before.
"Phantom of Heilbronn"
Cotton swab sticks used for DNA testing were contaminated
The unknown female suspect, dubbed "the phantom of Heilbronn," was never seen at the scene of any of the crimes. Police investigators have said they suspected that she could be homeless, a drug addict or even an itinerant used car dealer.
The police went on a widely publicized television appeal offering a bounty of 300,000 euros ($407,000) for evidence leading to her arrest, but no one came forward.
The DNA trail had led to 40 different locations in southwest Germany, France and Austria, with the last genetic fingerprint of the "phantom" found on March 18 in a school in the western German state of Saarland.
Police started to become suspicious when they looked into the case of a missing male asylum-seeker, who was believed to have perished in a fire several weeks ago. The investigators found DNA traces of the female "phantom" in the asylum seeker's file. A new DNA sample was taken from the fingerprint card and the "phantom" woman's DNA trace disappeared.
After watching the woman's DNA disappear, investigators began to consider the possibility that the cotton swabs used to collect the DNA were contaminated with the "phantom's" DNA before they were used at crime scenes.
At a press conference in Heilbronn on Thursday, the local public prosecutor and police from the German states of Baden-Wuerttemberg and Saarland admitted that they had been investigating the possibility of contamination since April 2008.
"An unknown person could have come into contact with the swabs, while they were being manufactured, packaged or delivered," said Bernd Meiners a spokesman for the public prosecutor in the western city of Saarbruecken.
Additional contamination likely
Microscopic human cells can easily contaminate the swabs
Police in Baden-Wuerttemberg have analyzed hundreds of unused swab sticks but have so far found nothing. But they say it is possible other batches were also contaminated.
According to Germany's Stern magazine, which broke the story that the police could have been chasing a phantom, the swab sticks were put through the proper sterilization procedures, but they could have still become contaminated from human cells in the form of skin particles, sweat, saliva or other bodily secretions.
In the meantime, female packers who work for the German company that supplies the swab sticks have given the authorities samples of their saliva to check whether the phantom's DNA is a match.
Police are also now testing the presumably sterile swabs used to collect evidence for contamination. New examinations of cotton swabs showed all likelihood of contamination said Ulrich Goll, justice minister in the state of Baden-Wuerttemberg, where police are spearheading the investigation.
"Something like this should not have happened," said the minister, who defended the police and forensic experts responsible for collecting the samples. "They were not able to tell if anything was wrong with the swabs."