A mysterious and mobile criminal stalked Germany. She was linked to seven murders and many other crimes. There were no clues to her identity — only her DNA, found at 39 crime scenes over two years. Was she a serial killer? A terrorist?
Nope. She worked at the factory that made the cotton swabs that the police used to collect DNA evidence. The supposedly sterile evidence collection tools were tainted.
As law enforcement becomes more reliant on high-tech methods, and as the public becomes more confident in them based on the influence of television forensics, it's important to remember that technological law enforcement is no more trustworthy than the people who design, manufacture, and use its tools.