Proof
Castro and Coyle wrote, "A blood presumptive test should never be taken as a final measure, and should always be followed by confirmatory testing at the forensic science laboratory before making the statement in court that a sample is human blood." The HemaTrace test has a better lower limit of detection than luminol does.
Machiavelli's argument is astonishing. He says that a confirmatory positive test for blood is proof of blood but that if it's negative, this is not proof of the absence of blood and that therefore there is still reliable evidence of blood. And we don't even have a confirmatory test. Machiavelli maintains that such a test cannot in any case provide proof of absence.
This is ultimately a casual reversal of the burden of proof and it's entirely invalid. It is earth shatteringly bizarre that the testimony of the key prosecution expert witness - the chief forensic investigator - is that the luminol hits are not blood and yet the Nencini court permits itself to conclude that they are blood.
Machiavelli is two tests short of evidence of blood - the field TMB test and the confirmatory laboratory test. He is also short of ANY expert opinion that would support the contention that there is blood. Remember, even Stefanoni says it is not blood.
Luminol positive/TMB negative results would not go before a British jury - I don't believe they would go before an American jury, other than by the choice of defence counsel as exonerating evidence. A prosecutor does not want this before the court - except in Italy.
The burden here is for Machiavelli to show:
1) A case history where these results were accepted by a court as evidence of blood.
2) An expert testimony or at least conclusive experimental data demonstrating that following a TMB negative test, it is safe not to proceed to confirmatory testing, ignore the TMB result and proffer as evidence of blood a positive luminol test conducted prior to the TMB test.
Machiavelli will not be able to accomplish either and cannot be allowed to prevail with a fatuous argument, which relies on imposing an empty philosophical trick whereby the innocent must demonstrate their innocence by proving a negative when he maintains that it is impossible to prove a negative, whatever you do.
Pick a card, he is saying - whichever card you pick cannot help you. If we could go back in time, do the analysis again and in it's entirety, it's not going to help you. You cannot escape. Whatever you do, I can still say it's blood.