DNA False Positives
A story about a very expensive series of false positives. The German police spent years and millions of dollars tracking a mysterious killer whose DNA had been found at the scenes of six murders. Finally they realized they were tracking a worker at the factory that assembled the prepackaged swabs used for DNA testing.
This story could be used as justification for a massive DNA database. After all, if that factory worker had his or her DNA in the database, the police would have quickly realized what the problem was.