In the beginning of the episode when the wife is pouring wine into the glass, you can clearly see a reflection of the studio's lights in the glass. Although we can see that several candles in the room are lit, they would not create the reflection seen in the glass.
Contaminated cotton swabs
The story is most likely based on the real 'Phantom of Heilbronn' case. DNA of an unknown female was found on 40 crime scenes in Germany, Austria and France from 1993 to 2009, including six murders. In late March 2009, investigators came to the conclusion that the "Phantom" criminal did not exist, and the DNA recovered at the crime scenes had already been present on the cotton swabs used for collecting DNA samples.