Negative controls and the police

Oh wow. In the last few years, the German police hunted a woman they only know from her DNA, which had been found at over 40 crime locations all over Germany and Austria (including the murder of a police officer in Heilbronn). Now, they slowly come to the conclusion that a charge of DNA collecting equipment got contaminated by a female employee... Running negative controls would have been really useful, no? (German source: stern.de, via: lawblog.de)