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For over a decade, police desperately searched for a serial killer whose DNA was found at countless crime scenes across Europe.
The figure came to be known as the 'Phantom of Heilbronn' or the 'woman without a face' and eluded police for years, seemingly taunting them.
Between 1993 and 2009, her DNA was picked up at over 40 crimes in France, Austria and Germany, varying in degree of seriousness, from murder and drug use to burglary and robbery.
But when they came to check her samples on their databases, they couldn't find a trace of her. Nothing.
The first time her DNA was found was on a teacup next to the body of a 62-year-old woman who had been strangled to death in her home in Idar-Oberstein, Germany in 1993.
Eight years later, it came up again: another murder.
This time it was a 61-year-old man who had been found dead in his home in Freiburg, and like the old lady, he too had been strangled.
Police found the mysterious woman's DNA in a kitchen drawer, and due to the similar methods of killing, they believed they had a serial killer on their hands.
After a few months, the 'woman without a face' popped up again, and again, and again.
Five months after the second murder, her DNA was detected on a heroin syringe found in a playground, on a discarded biscuit at the scene of a burglary and on a stolen car in Heilbronn, among others.
One of the most perplexing of cases, though, was that in May 2005, after a man had shot his own brother.
Somehow, the woman's DNA was found on one of the bullets used.
Two years later, her DNA was once again discovered, this time on the dashboard and the back seat of Michèle Kiesewetter's patrol car.
The 22-year-old police officer and her 25-year-old partner were on their lunch break when two men got into the back of the car and shot them in the head, killing Ms Kiesewetter and injuring her partner.
It was then that the killer began to be known as the 'Phantom of Heilbronn' and a €300,000 (£255,000) reward was put up for anyone that could provide any information on who they were.
All in all, her DNA was present at 40 crime scenes in several countries. But how?
Well, far from being a mastermind criminal who was evading police at every turn, the truth is much less sinister.
The officers who had worked on the crime scenes had all been using swabs that had been contaminated by a worker at a factory in Bavaria, Germany.
So the 'Phantom' never existed.
Speaking back in 2009, Stefan König of the Berlin Association of Lawyers said the case showed the importance of not reaching conclusions based on DNA alone.
He said: "DNA analysis is a perfect tool for identifying traces. What we need to avoid is the assumption that the producer of the traces is automatically the culprit.
"Judges tend to be so blinded by the shiny, seemingly perfect evidence of DNA traces that they sometimes ignore the whole picture. DNA evidence on a crime scene says nothing about how it got there.
"There is good reason for not permitting convictions on the basis of DNA circumstantial evidence alone."
Police spokesperson Josef Schneider said at the time: "This is a very embarrassing story."
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