A DNA profile from forty scenes came out of the supply box

The DNA profile that the German police chased for sixteen years came out of the box of cotton swabs in their own police stations. They found that out in March 2009. Until that month, the case had a novelist's name and a victim with a name and a surname.

Michèle Kiesewetter was 22 and wore the uniform of the police force of Baden-Württemberg, a German state. Shortly before two in the afternoon on 25 April 2007 she parked her patrol car on the Theresienwiese in Heilbronn, the open ground where the fair is set up, to eat something with her partner. Someone walked up behind them and shot them both in the head. She died there. He survived with a brain injury and could remember nothing. Inside the car, technicians found a female DNA profile, and that profile was already in the database.

It had first shown up in 1993, in Idar-Oberstein, a town in western Germany, on the teacup of a woman strangled in her own house. After that it kept surfacing in places with nothing to do with one another: houses broken into in Bavaria, cars stolen in Austria, a caravan, a syringe dropped in a wood, a school's coin box. Forty scenes spread across Germany, Austria and France over sixteen years. The German press christened her “die Frau ohne Gesicht”, the woman without a face: a criminal who did everything, moved without rest and left no witness, no motive and no face.

The criminal profiles sketched a young woman with a knack for improvising that matched nothing on record and, they said, probably from Eastern Europe. A special task force was set up, archives across half of Europe were combed through, and the whole of Heilbronn lost years of police work chasing her.

The case collapsed in March 2009, and it collapsed sideways. In France, investigators were trying to identify the burnt body of a missing asylum seeker. To do that, they went looking for DNA in the fingerprint the man had left years earlier on his own asylum application. The lab returned an impossible result: the profile of the woman without a face. Impossible, because that body was a man's.

The only thing the 1993 teacup, the 2007 patrol car and that body in France had in common was the cotton swab that had been rubbed over them.

The cotton swabs the local police used to take samples were mass-produced for medical use. They were sterile, which means free of live bacteria, and they had never been sold as free of human DNA: nobody had thought that would be necessary. On the packing line worked a woman who, handling them, left her own cells on the cotton. Every time an officer rubbed a door handle, a cup or a steering wheel with one of those swabs, he picked up the genetic trace of the scene and, along with it, that of a woman who had never left her packing plant.

The scandal ended in an international standard: in 2016 the ISO published 18385, which requires forensic collection material to be manufactured and certified free of human DNA. Seven years to change a box of cotton buds. The Kiesewetter murder was solved by another route in 2011, when the two officers' service weapons turned up in the hands of the neo-Nazi group NSU.

Of those forty scenes, not one was closed with an arrest based on that profile. The only person identified in sixteen years of searching was a woman on a packing line.