Lousy DNA analysis fools German police
The mysterious phantom killer the German police was searching after for years has finally been identified: it is a cotton swab. The photo below shows the wrongdoer after its arrest by a police investigator.
The search was extensive and sometimes extremely dangerous as you can see on this top secret snapshot taken by accident in 2004 (showing two brave cops hunting the dangerous phantom, doing their very best). Unfortunately, they grabbed the wrong person at that time.
Now, however, after DNA traces of the phantom (pointing at an unknown, criminal woman) have been found at 40 crime scenes, the police was successful. After spending millions of Euros and spinning the wheels of a 100-person investigation unit searching for “The Woman Without a Face” - who had been linked to six murders as well as to summerhouse burglaries - the German police revealed that they have been chasing after the DNA of a factory worker who handled the cotton swabs used by police lab workers.
In other words: the mystical person, often described as “the country’s most dangerous woman”, doesn’t exist a bit (or, more precisely, is a contamination on cotton swabs).
Ouch!!
The investigators suspect that certain batches of cotton swabs were contaminated before delivery. Although cotton swabs are sterilised before being used in investigations, they are often contaminated by human DNA from skin or sweat. Every forensic scientist who is in his right mind knows that and uses DNA-free swabs (to get more information on contamination problems, read, for example, this review from 2005: “Identifying and Preventing DNA Contamination in a DNA-Typing Laboratory”).
To quote this review: “[…] It is often easier, less time-consuming and more reassuring to simply discard all solutions that have come into contact with samples that demonstrate contamination.” and “For equipment that cannot be treated with bleach, exposure to ultraviolet light can eliminate DNA contaminants.”
The German police’s experts didn’t heed these advices. They rather put a €300,000 reward on their phantom and continued fishing in murky waters.
Now, many forensic scientists wonder about the simple-mindedness of their police colleagues at the German LKAs (the State Offices of Criminal Investigation where DNA traces from crime scenes are analysed). Are such lousy DNA analyses more exception than rule there, or vice versa?
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