You were comparing apples and oranges and didn't realize you inadvertently undermined your position. Or, perhaps a better analogy is comparing the Mark One Eyeball with the world's best microscope.
Low Template DNA analysis has not been accepted in American courts and has only just begun being used in a few court cases. The primary reasons are difficulty in interpretation and the more stringent contamination control protocols required. Generally American forensic technicians find a
substance and then identify it and determine who that is through DNA analysis. For example, they found blood on that knife and determined it was the victim's DNA and therefore his blood. They didn't go searching for low template DNA transfers, they found
substances and then identified who that biological material belonged to which preserves its probative value. That way you can better determine what finding that substance
means like semen in a vagina, saliva from a bite wound, skin/blood underneath fingernails, hairs pulled out with the roots. They used the Mark One Eyeball in the analogical sense. Take a look at the flow chart of the FBI standards on
8 of this report (22 of the pdf) and notice that the
first step is determining the substance and if they can't do that they don't go further.
However when dealing with
low template DNA, especially when they don't even
bother to identify the substance, you may be finding low template transfers that don't indicate much of anything in some circumstances. Contamination itself is (generally) a low template transfer, which is why those who use the method above can claim very low rates of contamination: it's just less likely for greater amounts to transfer and those substances are less likely to do so than skin cells and the like which can get
anywhere.
However, in the murder room they went down to the picogram and the lowest registering alleles and they found
nothing of Raffaele and Amanda in the murder room, but plenty of Rudy Guede. They used the best microscope in the world and picked up any low level substance-unidentified transfer they could and they pretty much excluded the possibility Raffaele and Amanda were in that room that night. Some of Rudy Guede's DNA would not have been found employing the top method, but then again none of Guede's DNA had an innocent explanation at all, and frankly the bloody handprint, shoeprints, and the fleeing to Germany is all you'd need to convict him.
However going in six weeks later
looking for low level transfers after the scene has been trashed giving only lip service to normal forensic procedures let alone LT/LCN requirements and finding an unidentified substance which has one major contributor and a minimum of three male minor contributors is pretty much worthless forensically, especially knowing the item sampled somehow motivated around and ended up in a pile of trash! There's no way to pretend the sampling done from the clasp indicates what was on it directly after the murder, and not knowing the substance means it could be anything transferring from
anywhere at that point. Unlike Rudy, Raffaele had been in the girl's flat innocently during the week before the murder and most especially was there at the discovery, exerting himself at the door. Finding his DNA after six weeks in that blender doesn't prove a goddamn thing about the murder,
especially because absolutely
nothing of his was found on or around the body when the only real forensic investigation was done, the day of discovery when the body was found behind a locked door.
So please, no more comparing eyeballs and microscopes.
