“There is always the chance that something else is influencing the data, causing the link. Between 1993 and 2008 the police in Germany were searching for the mysterious ‘phantom of Heilbronn’, a woman who had been linked to forty crimes, including six murders; her DNA had been found at all the crime scenes. Tens of thousands of police hours were spent looking for Germany’s ‘most dangerous woman’ and there was a €300,000 bounty on her head. It turns out she was a woman who worked in the factory that made the cotton swabs used to collect DNA evidence.”