Oops!

For 15 years, police in southern Germany have been futilely tracking a female "serial killer" whose DNA (but little other matching physical evidence) was found at 40 crime scenes, including six murders. Only in 2007 did they begin to consider alternative theories, and in March 2009, a state justice minister announced that the case had been solved: The DNA matched up in the tests because the cotton swabs used to collect it had been contaminated at the factory (but authorities still have not determined which female factory worker inadvertently supplied the DNA).