Mach you are knowledgeable on many things, and your input here is helpful. But biology is not your forte, you really should not state as facts things that are not true.
What I stated is just true - I would add, rather
obviously true - and I will paste it:
Machiavelli said:
1. There is no need to have detectable amounts of blood, in order to have DNA. And there is no need to have find blood at all, in order to find a murder weapon. DNA is, by far greater concentration than blood, in any other possible tissue a murder weapon would retain: muscle cells, bone, chartilage, epitheliums etc.
2. It's not even remotely possible to detect blood on the scale of DNA detection though a TMB test. The amounts required to detect DNA are by may magnitudes smaller. DNA can be duplicated (its amount amplificated), hemoglobine cannot. TMB has a true detection threshold, not just cautionary conventions like DNA.
3. The DNA was extracted from a sample collected from thin scratches on the blade. Those scratches are visible in crime photographies. The defence denies even the existence of the scratches.
4. What Chris says isn't correct science (see 2.).
You say:
Bone and cartilage are connective tissue, cartilage in particular is almost cell free and will contain very little DNA. Bone cartilage and muscle would have been seen when the knife was examined, in fact did not Stefanoni in fact observe cellular material? Cellular material that turned out to be starch granules? The presence of which indicates that the knife had not been thoroughly cleaned? So the knife was examined for the type of material you refer to and it was absent. The catalytic tests for haemoglobin are very sensitive and can detect only a few molecules. to get a DNA profile you need intact many DNA molecules.
Connective tissues contain lesser concentrations per volume unit of cells nuclei compared to muscular tissue and epithelial tissues. But they still contain more DNA than blood.
Anyway the point is that your punctualization of specificities of some conenctive tissues is just irrelevant. It is just irrelevant to the argument how big DNA concentrations connective tissue contains.
On the other hand, the statement that muscular cells or other cells would have been seen when the knife was observed is plainly an arbitrary statement contradicting the obvious fact: the residual biological material was in microscopic amount, it was sticking inside a microscopic scratch on the metal, it was invisible to the naked eye or to optical magnifiers as much as the bioloical material that was found on the blade handle. Which was, please note, certainly invisible. And obviously those who clened the knife they believed it was clean.
It is logically false to state that the presence of starch indicates that the knife had not been "thoroughly" cleaned (albeit we can reserve a discussion to the concept of "thoroughly"). Pay attention: the fact that something is dirty, does NOT mean that it had not been clean. My car is dirty now (it looks a bit), but I washed it thoroughly about a week ago.
Starch can originate from the corn starch used as lubricator on latice gloves (of the several experts who manipulated the knife, those who opened the handle etc.), or can be the result of using the knife during the four days subsequent to the murder, of of it being placed in a kitchen drawer possibly rather dusty and together with a bread knife, or may be a residual sticking between the blade and the handle that they failed to clean thoroughly.
In all these events, you cannot deduce anything from its presence.
Haemoglobin is a 'tough' molecule it is resistant to cleaning and will get in to crevasses. DNA is relatively soluble, and degrades easily so no profile is extractable.
It doesn't change a comma of what I said. You can still detect the presence of human DNA even in minimal aounbt from an amount less than 4-5 picograms and sometimes even if fragmentary. Because you can multiplicate DNA. But you cannot detect the presence of haemoglobin from an absolute amount of picograms. In order to detect haemoglobin, you need a concentration, and the concentration must be an an absolute amount in the order of microliters. (ps: edited to specify: here I mean that the
total volume of the
water solution containing haemoglobin must be in the order of microliters at least, in order to detect haemoglobin by presumptive chromatic tests; thus, you need a concentration and thus, an absolute amount to start with, that means not just 5/6 red cells).
The quantity of haemoglobin is massively greater than DNA in blood. If this knife were the murder weapon it cut a major vessel, causing massive bleeding, it would have been covered in blood. The ratio of haemoglobin to blood is orders of magnitude different than any differences in sensitivity testing, 30,000,000,000 : 1. Check the literature. Read the references given above.
But this doesn't change at all the fact that also the amount threshold to detect haemoglobin is massively higher. It is in fact a common occurrence to detect DNA but not be able to detect haemoglobin on latent traces, also on obvious blood traces, and we saw this on this case too. Several faint blood stains were negative to TMB (for example Amanda's ear blood drop on her pillow or some of the "cat blood" stains downstairs). Luminol is more sensitive but still the magnitude of detectable DNA amount is by several magnitudes smaller than the absolute amount of haemoglobin needed.
As a simple sense check, take the luminol positive traces that you ascribe to being blood. They gave a strong presumptive test for blood, but they were negative for DNA.
Well, actually they were positive to Knox's DNA, but three of them were also positive to Meredith's DNA.
So three of the nine luminol traces were in fact still positive to Meredith DNA, despite the traces had been exposed to light, bacteria and environmental degradating factors for over 46 days. You address the remaining ones, those that were not positive; however I point out that the same crime scene, anyway (as I explained above), also offers the contrary occurrence, that is: DNA was found on traces that were negative to presumptive tests, and presumptive tests were negative on traces which were likely blood. And a side note: the luminol traces are not even really fit to your example, since they are still negative to TMB (and TMB, which is "by far" less sensitive than luminol, is the test that was performed on the knife).
As an aside I also would argue that the relative ratios of Knox and Kercher DNA also prove that Knox DNA could not have arisen at the time of the crime if the knife was used in the crime. To be put simply any knife used in the way proposed would contain far more DNA of the victim than the wielder, any cleaning would clean the DNA of victim and wielder equally. The ratios would remain the same.
All depends on timings and roles. The wileder may be here also the washer of the knife. So may well leave his(her) DNA while washing the knife. The ratio is determined by one being the washer and the other being the "washed away" profile.
But here it's kind of linking "nothing" to "something". Maybe what the judge is saying is more like:
