Continuation Part 22: Amanda Knox/Raffaele Sollecito

[Bill Williams]

*sigh*

It would well befit Vixen to do even a modicum of research.

Sebaceous glands are microscopic exocrine glands in the skin that secrete an oily or waxy matter, called sebum, to lubricate and waterproof the skin and hair of mammals. In humans, they occur in the greatest number on the face and scalp, but also on all parts of the skin except the palms of the hands and soles of the feet.

https://en.wikipedia.org/wiki/Sebaceous_gland


And just to clarify, it's sebaceous fluid that contains DNA. Sweat in and of itself doesn't contain any DNA, except for when it is mixed with sebaceous fluid (sebum) - indeed one of the purposes of sebaceous excretions is to emulsify with sweat on the skin to modulate evaporation rates and thus cooling rates. So any sweat present on the palm or the inner face of the fingers is very unlikely to contain DNA in any measurable quantity. Which in turn leads to the conclusions reached by Vecchiotti and Filippini in their report. A report which Vixen appears not to have read, even in abstract form...........


ETA: I missed out the word "via" in my parentheses in my previous post ("chiefly sweat" should have read "chiefly via sweat"). As written, I might have given the misleading impression that sebaceous fluid was mainly sweat, which of course is not what I was meaning to convey. I was meaning to say that most sebum deposits occur when the sebum is deposited (via direct touch or fluid drops) within a sweat carrier.

It was by this method that I was able to prove that it was me who brought the ribs to the Stacyhs ex-picnic.

Acbytesla didn't show.

 

[LondonJohn]

It was by this method that I was able to prove that it was me who brought the ribs to the Stacyhs ex-picnic.

Acbytesla didn't show.

Now now Bill!!! But it does raise in my mind how different a game Cluedo (US = "Clue") would be if there was reliable low-template DNA evidence available

Incidentally, before our favourite counterweight starts nit-picking about sweat and DNA, I perhaps ought to add that sweat can also sometimes contain DNA by virtue of carrying dermal or epidermal skin cells, or hair fragments, or blood from surface contusions or cuts. But it's pretty well understood now that non-sebum sweat (e.g. the sweat from the palms or inner faces of the fingers) does not generally contain sufficient DNA from such sources as to enable analysis and identification, even at current low-template capabilities.

 

[Bill Williams]

Now now Bill!!! But it does raise in my mind how different a game Cluedo (US = "Clue") would be if there was reliable low-template DNA evidence available

Incidentally, before our favourite counterweight starts nit-picking about sweat and DNA, I perhaps ought to add that sweat can also sometimes contain DNA by virtue of carrying dermal or epidermal skin cells, or hair fragments, or blood from surface contusions or cuts. But it's pretty well understood now that non-sebum sweat (e.g. the sweat from the palms or inner faces of the fingers) does not generally contain sufficient DNA from such sources as to enable analysis and identification, even at current low-template capabilities.

You're going to keep after me until I get serious. So be it.

Her niblets contends that Knox wiped blood off of her hands in the bathroom. Yet there is no indication in that theory (synoptically combined with all the other evidence that even if true still does not demonstrate guilt!!!!).......

....... that indicates how Knox was supposed to have got all that blood on to her! There is certainly no indication that Knox was ever in the murder room, so where was she supposed to have got this on to herself?

Indeed, that is exactly what Marasca/Bruno mean when in September 2015 they include in their M.R. that that factoid was claimed by someone down the line, but by itself means nothing even if true, and especially when considered (scary word alert!!!!) SYNOPTICALLY with all the other stuff claimed.

That scary word is a slap in the face to Chieffi's use of the word "osmotically" in his 2013 M.R. which annulled Hellmann's acquittal. I'll see your osmosis and raise you a synoptic.

Ok, can we now get back to Stacyhs's ex-bar be cue. Like I noted, acbytesla did not show - one of Stacyhs's most short-lived flings.

 

[acbytesla]

It was by this method that I was able to prove that it was me who brought the ribs to the Stacyhs ex-picnic.

Acbytesla didn't show.

As much as I like Stacy and you Bill, I can't be a third wheel.

 

[Bill Williams]

As much as I like Stacy and you Bill, I can't be a third wheel.

Would it have killed you to at least have had the Cole slaw delivered? The whole Stacyhs ex-beau barbecue was without cole slaw.

 

[Chris_Halkides]

cell-free DNA

In doing a quick google search on sweat DNA, I found a comment at one entry of Evidenceprofblog from one Christopher Halkides: One, unless one performs a separate test, one should not speculate as to the tissue or fluid which deposited the DNA. Two, sebum is known as a potential source of touch DNA (“DNA fingerprinting secondary transfer from different skin areas: Morphological and genetic studies, ” doi:10.1016/j.fsigen.2014.03.005). Three, there is DNA in sweat (“Cell free DNA as a component of forensic evidence recovered from touched surfaces” doi:10.1016/j.fsigen.2011.01.004; link to abstract): “n this investigation, the presence of CNAs in sweat was detected on 80% of healthy individuals tested, with an average concentration of 11.5 ng of cell free DNA recovered per mL of cell free sweat. The mechanism for diffusion of CNAs into sweat is currently unknown, but is thought to be analogous to the excretion of other metabolites in sweat through sweat ducts.”

 

[LondonJohn]

In doing a quick google search on sweat DNA, I found a comment at one entry of Evidenceprofblog from one Christopher Halkides: One, unless one performs a separate test, one should not speculate as to the tissue or fluid which deposited the DNA. Two, sebum is known as a potential source of touch DNA (“DNA fingerprinting secondary transfer from different skin areas: Morphological and genetic studies, ” doi:10.1016/j.fsigen.2014.03.005). Three, there is DNA in sweat (“Cell free DNA as a component of forensic evidence recovered from touched surfaces” doi:10.1016/j.fsigen.2011.01.004; link to abstract): “n this investigation, the presence of CNAs in sweat was detected on 80% of healthy individuals tested, with an average concentration of 11.5 ng of cell free DNA recovered per mL of cell free sweat. The mechanism for diffusion of CNAs into sweat is currently unknown, but is thought to be analogous to the excretion of other metabolites in sweat through sweat ducts.”

This Halkides fellow is indeed smart and well-informed!

Do you subscribe to Vecchiotti's/Filippini's contention that non-sebaceous sweat, while it may contain DNA from CNAs, would usually not result in the transfer of sufficient DNA to another surface to enable forensic analysis and reliable matching?

 

[Bill Williams]

This Halkides fellow is indeed smart and well-informed!

Do you subscribe to Vecchiotti's/Filippini's contention that non-sebaceous sweat, while it may contain DNA from CNAs, would usually not result in the transfer of sufficient DNA to another surface to enable forensic analysis and reliable matching?

At the Stacyhs barbecue, Halkides did the magic show. When we asked him how he'd done the tricks, he said, "Stefanoni never released her EDFs and neither will I!"

 

[Vixen]

Now now Bill!!! But it does raise in my mind how different a game Cluedo (US = "Clue") would be if there was reliable low-template DNA evidence available

Incidentally, before our favourite counterweight starts nit-picking about sweat and DNA, I perhaps ought to add that sweat can also sometimes contain DNA by virtue of carrying dermal or epidermal skin cells, or hair fragments, or blood from surface contusions or cuts. But it's pretty well understood now that non-sebum sweat (e.g. the sweat from the palms or inner faces of the fingers) does not generally contain sufficient DNA from such sources as to enable analysis and identification, even at current low-template capabilities.

People often wipe their face when nervous; criminals often leave behind DNA or fingerprints precisely because of this greasy perspiration. To say there is no way Raff could have left his DNA via his fingers is bunk.

 

[acbytesla]

Would it have killed you to at least have had the Cole slaw delivered? The whole Stacyhs ex-beau barbecue was without cole slaw.

I'm sorry, I didn't know that was protocol.

 

[LondonJohn]

People often wipe their face when nervous; criminals often leave behind DNA or fingerprints precisely because of this greasy perspiration. To say there is no way Raff could have left his DNA via his fingers is bunk.

Oh dear.

Read my initial post on this subject again. And read the Vecchiotti/Filippini study. Where do either I or V/F state or imply that this study indicates that "there is no way Raff could have left his DNA via his fingers"?

Now have another go with the blind, uninformed contrarianism

 

[Planigale]

Now now Bill!!! But it does raise in my mind how different a game Cluedo (US = "Clue") would be if there was reliable low-template DNA evidence available

Incidentally, before our favourite counterweight starts nit-picking about sweat and DNA, I perhaps ought to add that sweat can also sometimes contain DNA by virtue of carrying dermal or epidermal skin cells, or hair fragments, or blood from surface contusions or cuts. But it's pretty well understood now that non-sebum sweat (e.g. the sweat from the palms or inner faces of the fingers) does not generally contain sufficient DNA from such sources as to enable analysis and identification, even at current low-template capabilities.

Sweat is cell free secretion of salt and water. There may be epithelial cells shed along with sweat, but sweat is in itself cell free. Sebaceous glands are part of hair follicles (which are absent on the palms and soles), produce sebum an oily substance. These are 'holocrine' glands. The cells accumulate oil within them then the cells rupture releasing the cell contents, mostly oil, but also the cells DNA. This is not new science, merely a clear description of what is known.

 

[LondonJohn]

Sweat is cell free secretion of salt and water. There may be epithelial cells shed along with sweat, but sweat is in itself cell free. Sebaceous glands are part of hair follicles (which are absent on the palms and soles), produce sebum an oily substance. These are 'holocrine' glands. The cells accumulate oil within them then the cells rupture releasing the cell contents, mostly oil, but also the cells DNA. This is not new science, merely a clear description of what is known.

Agreed. Pure sweat is undoubtedly DNA-free. But the salient point here is whether non-sebaceous-area sweat (especially from the palm of the hand or the inner surfaces of the fingers) typically contains enough "contaminants" in the form of skin cells or other sources of DNA to leave sufficient touch DNA to enable typing.

In other words, if a person touches a (eg) door handle with his hand and transfers small (but typical) amounts of sweat from his hand to the door handle, would there usually be enough "primary" DNA in that touch transfer (in the form of skin cells or white blood cells embedded in the sweat) to enable DNA typing? Or would it usually be necessary for that person to have (for example) previously touched (eg) his face to transfer DNA-containing sebum to his hand, and then transferred that DNA-containing sebum (together with sweat from his palm) to the door handle? Because, importantly, this would immediately imply at least a secondary transfer route for the DNA (face to hand - hand to door handle).

 

[Welshman]

As DNA is being discussed, there is an important question to ask about DNA transfer. Besides the dubious DNA on the clasp, Amanda and Raffaele left no forensic traces such as DNA. PGP have argued that biological traces such as DNA do not transfer easily and it is perfectly normal not to leave forensic traces. In view of this to argue that Amanda and Raffaele are innocent on the basis they left no forensic traces is not valid. If I remember correctly even a PIP accepted this. Machiavelli argued that the forensic traces left by Guede were fairly weak which supported the notion biological traces don't transfer easily.

How valid is the notion that biological traces don't transfer easily. Is it credible that Amanda and Raffaele could have taken part in the murder of Meredith without leaving forensic traces.

 

[Chris_Halkides]

multiple DNA transfer

As DNA is being discussed, there is an important question to ask about DNA transfer. Besides the dubious DNA on the clasp, Amanda and Raffaele left no forensic traces such as DNA. PGP have argued that biological traces such as DNA do not transfer easily and it is perfectly normal not to leave forensic traces. In view of this to argue that Amanda and Raffaele are innocent on the basis they left no forensic traces is not valid. If I remember correctly even a PIP accepted this. Machiavelli argued that the forensic traces left by Guede were fairly weak which supported the notion biological traces don't transfer easily.

How valid is the notion that biological traces don't transfer easily. Is it credible that Amanda and Raffaele could have taken part in the murder of Meredith without leaving forensic traces.

There is a paper with a nice graphic on multiple transfers of DNA. 'Following the transfer of DNA: How far can it go?" by van Oorschot and collaborators from 2013 in Forensic Science International. The scale on the Y-axis is quite large. After each transfer, there is some loss of DNA. The original source of the DNA (wet blood, dried blood, or touch) and the substrate (cotton or glass IIRC) both have an effect on the number of transfer events.

Tertiary transfer by contact has been documented in at least two studies, perhaps more. In two recent studies an unknown DNA was also transferred multiple times.

 

[Chris_Halkides]

cell free DNA

This Halkides fellow is indeed smart and well-informed!

Do you subscribe to Vecchiotti's/Filippini's contention that non-sebaceous sweat, while it may contain DNA from CNAs, would usually not result in the transfer of sufficient DNA to another surface to enable forensic analysis and reliable matching?

I don't have a strong opinion on that question yet. It depends in part on how much sweat one transfers. I think that we don't know as much as there is to know about cell free DNA at this point. "Presence and potential of cell free DNA in different types of forensic samples." Forensic Sci Int Genet. 2013 Feb;7(2):316-20. doi: 10.1016/j.fsigen.2012.12.005

 

[Chris_Halkides]

DNA degradation in the presence of bleach

The attached figure is from a 2011 paper by Bruce McCord and collaborators, "An Investigation of the Effect of DNA Degradation and Inhibition on PCR Amplification of Single Source and Mixed Forensic Samples. This electropherogram shows what happens when bleach (bottom panel) or hydrogen peroxide (middle panel) reacts with DNA but not to the point of complete destruction of the DNA. This confirms a prediction I made long ago, that the peak heights would get smaller, moving left to right in the electropherogram. In other words, the longer a piece of DNA is, the more likely that it will be damaged when a random agent acts upon it. Once it is damaged, it cannot be replicated by the polymerase chain reaction, leading to a smaller peak height. That prediction (which wasn't really much of a stretch) was based on work done on DNA degradation, some of which is discussed in Jason Gilder's Ph.D. thesis, chapter 3. The DNA from 36B, supposedly from the extraction of the knife, has peaks that vary in size, but I am unable to discern a clear downward trend. Therefore, it is difficult to argue that the kitchen knife was cleaned with bleach or hydrogen peroxide IMO.

 

[LondonJohn]

Ahhhh doesn't it feel good to be back on an informative and educative discussion of weighty relevant topics

Thanks Chris. This is all very interesting.

 

[Bill Williams]

Ahhhh doesn't it feel good to be back on an informative and educative discussion of weighty relevant topics

Thanks Chris. This is all very interesting.

Oh sure. You didn't have to endure a barbecue with no cole slaw.

 

[Vixen]

As DNA is being discussed, there is an important question to ask about DNA transfer. Besides the dubious DNA on the clasp, Amanda and Raffaele left no forensic traces such as DNA. PGP have argued that biological traces such as DNA do not transfer easily and it is perfectly normal not to leave forensic traces. In view of this to argue that Amanda and Raffaele are innocent on the basis they left no forensic traces is not valid. If I remember correctly even a PIP accepted this. Machiavelli argued that the forensic traces left by Guede were fairly weak which supported the notion biological traces don't transfer easily.

How valid is the notion that biological traces don't transfer easily. Is it credible that Amanda and Raffaele could have taken part in the murder of Meredith without leaving forensic traces.

For Raff's DNA to realistically transfer from the door (say) to the bra clasp by a forensic glove, the original would need to be reasonably moist for the latex glove to pick it up (latex probably not very friendly towards preserving DNA) and then the glove to press down on the metal clasp fairly firmly. This stickability is enhanced by the lipids (fats) within sebaceous glands (mostly on the scalp and face), which also aids the impression of one's fingerprints.

It is highly vanishingly remote Raff's DNA would have survived on the door - in a moist, oily form - long enough for such a secondary transfer to take place. At his age, he likely was "a spotty youth" with lots of DNA carried in his sebaceous gland sweat, but it ain't necessarily so. There are lots of dry skin conditions, such as psoriasis, which would carry very little sebaceous lipids at all.