The protocols she skipped and lied about are the ones where she determines if there was anything on the blade or anything on the swab she extracted. That's rather important if you stop and think of it! The 'too low' is the same result she would get if there was nothing on the swab when she extracted it. That lab processed hundreds of item with Meredith Kercher's DNA, there was nothing on the knife
except debris and food particles which show the knife wasn't scrubbed clean to remove all blood traces and it
tested negative for blood with the two tests Stefanoni performed and the
one the independent experts did. As she got the same result as nothing when she tried to quantify what she extracted, the irresistible inference is that that smidgin of DNA came from her lab. It registered 'peaks' of
20-40 RFUs (as opposed to 1000-2000) which with an Identifiler kit and 28 cycles suggests around
10 picograms of material, around 1 nanogram (1000 picograms) is what that equipment is designed for. One reason for those minimum DNA thresholds (she used 100 RFUs on most samples, 50 RFUs was the lowest in use at the time) is to
prevent 'profiling' contamination.
However she lied about the amount in court, claiming she
quantified it with Real Time PCR amplification and got a result of 'some hundreds of picograms.' At that juncture her (paper) records weren't available and they avoided allowing the defense to see them until July 30th, 2009 which is where much of this was discovered, including her lies about the TMB negatives she also hid. To this day she has managed to avoid releasing the EDFs, the electronic data which those electopherograms are generated off of, defying the request of the independent experts and the judge.
So to make a long story shorter, there's no reason to think that DNA was ever on the blade and numerous reasons to think it wasn't. There's no reason to think it was even in the sample she put into the extractor, and in fact she could even have photoshopped it, though that's not what she did, instead she just advanced contamination as evidence and lied about it to hide that.
To use your example it would be the equivalent of the police finding absolutely nothing in the trunk, but taking out the trunk rug and claiming to the court they'd found a pill. Then when the records were shown it was determined there was no pill, instead she tested the trunk rug in a lab which tested hundreds of items with ecstasy dust and what she actually claimed she found tested negative first but then when performing more tests in that dirty lab claimed she found 1% of a pill by ignoring the lab rules which automatically discount that as they know that picking up minute quantities like that happens when you test hundreds of items that
do have ecstasy dust on them. Oh, and she refuses to actually show the results of the test but just a piece of paper that says she found a minute amount of dust and won't let you see the entire results of those tests come hell or high water.
