We're not through. Laboratories performing LCN rely heavily on what are called “negative controls.” The following quote is from The Law Society of Scotland's publication at:
http://www.journalonline.co.uk/Magazine/52-2/1003857.aspx
“In forensic science the fact to be established is that the DNA profile originated from the material recovered from a crime scene or a suspect, not the investigator, the laboratory, packaging, or analytical instruments. A “negative control” is set up by simply processing a “blank” sample that has no DNA. All being well, this control will not show any DNA. The presence of DNA in the negative control illustrates that there has been a source of contamination in the analytical method. It does not, of itself, show where that occurred, merely that it has. The tradition over many years has been, for very sound reasons, that anything found in the “negative control” invalidates the analysis.
...even in a tightly controlled analytical procedure a significant number of supposedly negative controls give a positive result, i.e. they indicate the presence of DNA.”
Stefanoni apparently did not perform any negative controls with same system parameters as that used for the kitchen knife DNA. That's another deficiency.