Super,
Colmez made the case for retesting the knife, with the possibility of making the old result (the low template finding of Ms. Kercher's profile) more reliable. Whether her case is a good one or not is a matter for a separate comment. What the Carabinieri actually found was DNA that probably arose from Ms. Knox as a donor. Colmez should be asked how the fact of not finding Kercher's DNA impacts on the reliability of the first test. That was the whole point of doing the second test.
IIRC Ms. Knox was already shown to be a donor with respect to DNA on the handle; therefore, finding her DNA on the blade does not seem very surprising. However, the result is actually more exculpatory than inculpatory. Now the prosecution is asserting in effect that one can clean a knife of blood completely, yet still leave two traces of DNA on the blade, as well as starch on the blade. I am with Professor Budowle: The prosecution's case defies reason on this point. Perhaps Ms. Alexander will look into this question.
And there are still other questions to be asked, for example she could explore how many cases of DNA contamination exist where a route was shown vs. how many case of DNA contamination exist where a route is not known. This is one of the scientific errors perpetrated by the CSC...