Let me add this little DNA-act-of-stupidity-story.
A couple of years ago in Germany...there was this murder. DNA got collected. Couple of months go by, and they have a break-in that matches up with the DNA. Then another murder. Then a couple of Turks killed in a car. More DNA collected, etc.
Eventually, there’s a name tagged to this ‘woman’ (someone noted one passing glimpse of the suspect and the cops stuck to that idea of a woman). The name? The ‘phantom killer’. It was a nifty name and the news media covered this off and on. The suspect was thought to be between 16 and 19 years old....maybe having killed fifteen-odd people. A cop was eventually killed, and this really hyped up everything.
One day, by accident, one of the cops tagged a swab for examination for DNA but hadn’t ever used it from any crime scene. It was sterile.
Well....the swab came back with the DNA of the Phantom Killer. The cop went up the chain....it’s not possible.
So a team went off to Austria where these swabs were manufactured. The owner was a small-business guy. He really didn’t know the ultimate purpose of these swabs. He sold them to a company that wrapped them up and sold them to the cops as DNA collection devices.
The cops sat there and saw this older sweaty Austrian gal then pick up a whole bunch of the swabs with her barehands. Then they realized who the Phantom Killer was, or how corrupted the whole DNA process had become. They basically threw out their entire database on the Phantom Killer over night.
DNA isn’t all perfect, and I’d suspect this DNA is from some sales-lady who just happened to reach in as the dimwits bought the bag to check for anything inside. It may be that simple in the end.