For years there was the “Phantom”, a notorious criminal, haunting all of Europe. DNA testing revealed that it was a female and her crimes ranging from petty theft to murder were seemingly unrelated to each other. That each of them were done in different countries didn’t make solving the case any easier.
But eventually they did solve it. They found the woman working in a cotton swab factory. Turned out many police departments were using the wrong type of swabs. So there seem to be more than one way to incorrectly use cotton swabs.