DNA Analysis: Far From an Open-and-Shut Case

German police had been quietly tracking a serial killer for years but in 2007 the case exploded into headline news after the slaying of a young police officer in the city of Heilbronn. DNA evidence identified the suspect as the same individual who had been present at numerous murders, burglaries and break-ins but this latest development seemed to be a worrying escalation in violence. No one had ever seen the suspect's face but genetic analysis clearly identified her as a woman – an unusual characteristic for a serial killer, but only one of several extraordinary aspects to this progressively troubling crime spree. There was no apparent pattern to the crimes; she apparently struck widely and indiscriminately, even across the border in France and Austria. The only consistent information was the occasional sighting of a man near the scene, leading to speculation that the killer was transsexual. The media nicknamed the killer the Phantom of Heilbronn and the increasingly desperate police offered €300,000 for her capture.

The bounty was never collected. This was not because the serial killer evaded justice, but...