so as none of the DNA was from blood - How for example do you think DNA from the twins or June came to be in the moderator by contamination?
It was taken apart by people who had touched items containing DNA of the victims. Those people transferred minute amounts of DNA of the victims. If it was a substantial amount of DNA then it would mean the victims themselves had handled it. But we are talking about Tiny traces so small that they had to duplicate it just to get a sample large enough to be able to get some of the DNA markers. Had Nevill taken it apart to clean not only could he get his own DNA inside but that of any family members whose DNA he had a trace of on him but it's obvious he hadn't cleaned it prior to the murders and that the evidence handling did it.
There are very strict procedures in place for evidence handling today precisely because the ease of contamination. None of these existed at the time even the jury was free to touch all the exhibits and could have caused cross contamination.
LCN DNA is useful when someone's DNA is found who has no conceivable way for any of their DNA to get there by contamination. If you don't know the victim in any way and a trace of your DNA is on her panties you have a lot of account for. The only way to try attacking that evidence it to try to look at the evidence handling procedures to see if there is a way the lab could have caused the contamination which is why evidence handling is so important.
In the Kercher case they didn't follow any of the required DNA protocols and it was established Kercher's DNA was on the knife because it was already present in the lab and transferred there. This is why several courts including the final one that acquitted said this evidence had to be rejected and was improperly relied upon by the courts that convicted.
That DNA was not blood based either so the court also rejected it on that basis. How could it prove she was stabbed with it when it wasn't blood based? Then of course there was the problem of the knife in question not being capable of causing the wounds and not matching the shape of the knife that left the bloody outline so 3 different reasons it was meaningless.
You have to look at everything as a whole to see whether DNA means something or not. Sometimes it can include or exclude other times it is useless.
If DNA testing existed at the time then in this case instead of type testing the blood they removed they would have done DNA testing. Lincoln would have DNA tested the blood he removed as well. Neither the lab nor Lincoln preserved any of that material for later testing they expended it all and thus DNA testing can't serve any value in this case to further refine the blood in the moderator issue.
Nor is there any other issue in this case where DNA testing could help. Jeremy's DNA would be expected all over WHF as would be that of the victims. Just like their fingerprints would be expected all over. If Jeremy left a print in blood of the victims that would be a different matter because only if he were the killer could he have done so but he didn't.