Protocols in reality must be made compatible with many practical limitations (time, supplies, etc.). Real life is often imperfect, you can't expect ideal conditions as if they were a practical standard or reasonable expectation. You need to make the best of what you have, you can't always ask for the best.
Moreover, Stefanoni is not even the person in charge of the crime scene.
What matters instead is something else. The question to answer about the DNA findings (which is not the most important evidence in the trial anyway) is how did Sollecito's DNA come to the bra clasp. If there is any reasonably explanation why the specific finding of Sollecito's profile on the metal hook should be a probable event, without he taking part to the murder.
Attempts to attack Stefanoni are just mean attempts to divert the discourse, and to try to go around the question. No ranting of protocols and standards nor pretexts or specious unjustified insults against forensic scientists will change the finding and the point to answer: Sollecito's DNA is on the bra clasp, no alleged protocol breach would offer a probable alternative explanation, even if they dipped the bra clasp in a bucket of mud before collecting it that would not be helpful to Sollecito's defense: its DNA would still demand to be explained.
Well seeing as Sollecito had legitimate contact with Meredith Kercher just hours before she was murdered by Guede - and had visited the house on a number of occasions, there are a myriad of ways for his DNA to be transferred.
And all I have to say to Stefanoni is "Soap and Water!"