On the afternoon of April 25, 2007, Michele Kiesewetter, a 22-year-old police officer in the German city of Heilbronn, was shot dead in a parking lot. Kiesewetter had been on patrol with her partner, Martin Arnold, when the two officers pulled into the lot around 2 p.m. to have lunch.
Shortly afterward, a taxi driver alerted the police to a possible attack. When officers arrived at the scene, they found Kiesewetter hanging upside down from the open driver's side door, with a single gunshot wound to the head. Her partner, Martin, was also shot in the head but was still breathing. He recovered months later, albeit with lifelong disabilities.
The crime scene and the patrol car were meticulously examined. Both officers’ service weapons and handcuffs were missing. However, forensic experts recovered a crucial piece of evidence—traces of DNA inside the vehicle that did not belong to either of the victims. A database search revealed that the DNA matched that of an unidentified woman already wanted in connection with more than forty crimes—including homicide, robbery, and kidnapping—committed across Germany, Austria, and possibly France.
Police officers attend the funeral procession of Officer Michèle Kiesewetter in April 2007.
The unique DNA signature first surfaced in 1993 in Idar-Oberstein, a small town roughly two and a half hours northwest of Heilbronn. There, 62-year-old churchwarden and pensioner Lieselotte Schlenger was found strangled in her rented apartment. The murder weapon was a thin wire used to tie a flower bouquet. No fingerprints were recovered and no witnesses emerged. However, a swab taken from the rim of a teacup on Schlenger’s kitchen table produced a trace amount of genetic material—just enough to be analysed.
Eight years later, in March 2001, the DNA turned up again—this time at the scene of another murder in Freiburg. Josef Walzenbach, a 61-year-old antiques dealer, was found strangled with garden twine in his home. As with the Schlenger case, there was no further forensic evidence, no suspects, and no eyewitnesses. But once again, the same DNA profile appeared, still unmatched in any criminal database. Forensic experts determined only that the genetic material belonged to a woman, likely of Eastern European descent.
A few months later, the mysterious profile re-emerged in a setting far removed from murder. Seven-year-old Jürgen Büller was walking near his home in Gerolstein when he stepped on a discarded syringe lying on the sidewalk. Unfamiliar with the object, the boy brought it home, prompting alarm from his mother, who immediately took both her son and the syringe to be tested for HIV.
Lab tests revealed that the syringe contained traces of heroin—and the same female DNA. Investigators began to form a narrative: the unidentified woman was now believed to be a drug addict, possibly homeless, drifting across Germany and killing at random, perhaps to support her addiction.
This theory gained traction in the media. Kurt Kletzer, a well-known Viennese psychiatrist, speculated publicly that the suspect likely had a traumatic childhood, possibly raised in foster care and subjected to abuse. The image of a damaged, unpredictable, and violent woman—part addict, part drifter—began to take root in the public imagination.
In the years that followed, the mysterious woman’s DNA continued to appear at crime scenes across Germany, Austria, and even France. It was found on a half-eaten cookie discarded near the site of a trailer-home burglary in Budenheim, Germany; on a toy gun left behind after a 2004 gemstone heist in Arbois, France; and at the scene of a robbery at an optometrist’s shop in Gallneukirchen, Austria.
In Saarbrücken, Germany, a stone used to smash a window during a 2006 break-in carried traces of her DNA. The same DNA showed up in the ruins of a disused public swimming pool following a burglary, and at numerous other break-ins and home invasions across central Europe. There appeared to be no pattern, no consistent modus operandi. The only link between these disparate incidents was the recurring presence of a single woman’s DNA, connecting them all like the thread of an invisible hand. By the late 2000s, this unidentified suspect had been tied to nearly 40 crimes, both major and minor.
Police dubbed the unknown suspect the “Woman Without a Face.” But after the execution-style murder of officer Michele Kiesewetter, she gained another moniker: “The Phantom of Heilbronn.” Media outlets speculated about a female serial killer capable of slipping unnoticed across borders and crime scenes. Law enforcement agencies poured resources into tracking her down. Artists' sketches were made. Public warnings were issued. A reward of €300,000 was offered for any information leading to her capture.
Composite image of the Phantom of Heilbronn based on eyewitness accounts that was released to the public by the police.
But as the investigation dragged on, cracks began to appear in the theory.
How could one woman be involved in so many different crimes over such a wide geographic area? Why did no one had ever seen her, or no security camera had ever captured her image? Why did this phantom sometimes appear to work alone and other times alongside other? Why did her accomplice keep changing?
The inconsistencies piled up, but the DNA kept showing up. It was as if the Phantom were everywhere and nowhere at once.
Then, in 2009, the entire investigation unravelled. While probing the burned body of a male asylum seeker in France, forensic teams found the Phantom’s DNA once again. But this time, there was no logical explanation for its presence. The circumstances forced investigators to take a hard look at their own procedures.
A closer examination of the evidence collection process revealed the shocking truth: the cotton swabs used to gather DNA samples at multiple crime scenes had been contaminated before even reaching investigators. These swabs, manufactured by an Austrian medical supplier, had been tainted with trace amounts of DNA from a female factory worker during production.
The so-called Phantom of Heilbronn had never existed.
In the following investigation, it was revealed that several state police departments have been using contaminated cotton swabs from the same factory, Greiner Bio-One International AG. While cotton swabs supplied by Greiner Bio-One are were put through the proper sterilization procedures (used to kill bacteria, fungi and viruses), but still became contaminated with human cells in the form of skin particles, sweat, saliva or other bodily secretions. An investigator later told a news reporter in disbelief: “The things were double-packaged; we thought they were the Mercedes of cotton swabs.”
A technician swabs samples at the laboratory. Cotton swabs like these were used to collect DNA samples. Credit: Thirdman/Pexels
The revelation was both humiliating and devastating for law enforcement. Years of investigation, millions of euros, and countless man-hours had been wasted chasing a ghost. Worse still, the contamination had obscured real leads—most notably in the case of officer Kiesewetter’s murder, which remains officially unsolved to this day.
The incident exposed critical flaws in forensic protocol and led to sweeping reforms in evidence handling. The International Organization for Standardization (ISO) published the standard ISO 18385 in 2016 to define the requirements for producing consumables free of human DNA contamination designated for collecting biological evidence at crime scenes. Laboratories across Europe reviewed their procedures and standards for "DNA-free" collection materials were tightened.
The Phantom of Heilbronn case also raised doubts on the over-reliance on forensic evidence. “DNA analysis is a perfect tool for identifying traces,” said Stefan König of the Berlin Association of Lawyers. “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.”
References:
# “The black hole”. Spiegel
# “'Woman Without A Face' leaves German police in the dark”. The Sydney Morning Herald
# “Germany’s Phantom Serial Killer: A DNA Blunder”. Time
# “Germany hunts phantom killer”. BBC
# “'DNA bungle' haunts German police”. BBC
# “Hunt for The Woman Without A Face”. Mirror
# “Jill the tripper eludes her captors”. The Sydney Morning Herald
# “The mystery of the Phantom of Heilbronn”. ISO.org
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