The Phantom of Heilbronn and DNA testing.

Oops:

Police in Germany have admitted that a woman they have been hunting for more than 15 years may never have existed. Dubbed the “phantom of Heilbronn”, the woman was dubbed by police as the country’s most dangerous woman. Investigators had connected her to six murders and an unsolved death based on DNA traces found at the scene.

…Police are now acknowledging that swabs used to collect DNA samples may have been contaminated by an innocent woman – possibly during manufacture.