There's something deep in here but I'm not sure quite what:

Police in Germany hunted a sinister phantom killer for two years after finding the same DNA at 39 different crime scenes - only to discover that the source was a woman who made the cotton buds used to collect the sample! The case was one of the most puzzling in recent times. Hundreds of detectives in six specialist committees were set to work hunting the ominous female serial killer.

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