Yes that is the other side of the argument. I don't understand the DNA science well enough. As a layperson, all I can say is that I don't understand how you get a false positive when measuring for something like a DNA sequence unless there is cross-contamination, e.g. that the police themselves accidentally or intentionally put one person's blood onto an object. In this case, they would have to have gotten Knox's BF's blood from somewhere in his apartment and brought it over to the crime scene, and placed it on the bra clasp. This came up in the OJ case. To me, it doesn't sound like something likely to happen unless it is done intentionally.
- wolf