Continuation Part 22: Amanda Knox/Raffaele Sollecito

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Stacyhs said:
Well, he is sharp. Look what he does to a certain PGP on here. It's beyond entertaining to watch.
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In that case I'll stand aside. The problems of two people in this crazy world don't amount to a hill of beans. All I know is that you are getting on that plane.

We'll always have Paris.
 
Inside of us, we both know you belong with acbytesla. You're part of his work, the thing that keeps him going. If that plane leaves the ground and you're not with him, you'll regret it. Maybe not today. Maybe not tomorrow, but soon and for the rest of your life.
Ilsa: But what about us?
Rick: We'll always have Paris. We didn't have, we, we lost it until you came to Casablanca. We got it back last night.
Ilsa: When I said I would never leave you.
Rick: And you never will. But I've got a job to do, too. Where I'm going, you can't follow. What I've got to do, you can't be any part of. Ilsa, I'm no good at being noble, but it doesn't take much to see that the problems of three little people don't amount to a hill of beans in this crazy world. Someday you'll understand that.
[Ilsa lowers her head and begins to cry]
Rick: Now, now...
[Rick gently places his hand under her chin and raises it so their eyes meet]
Rick: Here's looking at you kid.
 
Bill Williams said:
Inside of us, we both know you belong with acbytesla. You're part of his work, the thing that keeps him going. If that plane leaves the ground and you're not with him, you'll regret it. Maybe not today. Maybe not tomorrow, but soon and for the rest of your life.
Ilsa: But what about us?
Rick: We'll always have Paris. We didn't have, we, we lost it until you came to Casablanca. We got it back last night.
Ilsa: When I said I would never leave you.
Rick: And you never will. But I've got a job to do, too. Where I'm going, you can't follow. What I've got to do, you can't be any part of. Ilsa, I'm no good at being noble, but it doesn't take much to see that the problems of three little people don't amount to a hill of beans in this crazy world. Someday you'll understand that.
[Ilsa lowers her head and begins to cry]
Rick: Now, now...
[Rick gently places his hand under her chin and raises it so their eyes meet]
Rick: Here's looking at you kid.
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You're really pushing this Bill.
 
Aaaand back to the topic of the thread!

One very interesting aspect of the recent academic paper on touch DNA co-authored by Vecchiotti is the contention that most low-template touch DNA is actually from sebaceous fluid (chiefly sweat) rather than epithelial skin cells. And that has interesting ramifications, since the human palm has no sebaceous glands and therefore cannot be the primary source of sebaceous DNA. And that in turn means that if sebaceous-origin touch DNA is found at, for example, a crime scene, then this must mean that it was either deposited by direct contact from a part of the body which does have sebaceous glands (e.g. the forearm or the chest or the face) or it was deposited by the hand via (at least) secondary transfer. And given that the vast majority of touch contact at anything like a crime scene is via hand contact, then this implies immediately that most low-template DNA found at the scene is likely the product of at least secondary transfer, and possibly tertiary transfer. Furthermore, the palm and the palm face of the fingers have hardened skin which is also frequently washed, and therefore the human palm or palm-facing fingers are less likely than other areas of the body to shed significant quantities of epithelial cells anyhow.

IIRC, it was never shown that Sollecito's apparent DNA on the bra clasp was epithelial in origin (in contrast with Guede's DNA on/in Kercher which was definitively identified as being epithelial in origin). It's therefore reasonable to wonder whether this was sebaceous DNA, in which case it would likely have to have endured (at least) secondary transfer in order to arrive on the bra clasp. And while of course it's arguable that this secondary route might be Sollecito sebaceous fluid - Sollecito hand - bra clasp, it's clearly reasonable to suggest that the route might involve an extra hop and be something like: Sollecito sebaceous fluid - door handle or door face - incompetent crime scene investigator - bra clasp (tertiary transfer).
 
LondonJohn said:
Aaaand back to the topic of the thread!

One very interesting aspect of the recent academic paper on touch DNA co-authored by Vecchiotti is the contention that most low-template touch DNA is actually from sebaceous fluid (chiefly sweat) rather than epithelial skin cells. And that has interesting ramifications, since the human palm has no sebaceous glands and therefore cannot be the primary source of sebaceous DNA. And that in turn means that if sebaceous-origin touch DNA is found at, for example, a crime scene, then this must mean that it was either deposited by direct contact from a part of the body which does have sebaceous glands (e.g. the forearm or the chest or the face) or it was deposited by the hand via (at least) secondary transfer. And given that the vast majority of touch contact at anything like a crime scene is via hand contact, then this implies immediately that most low-template DNA found at the scene is likely the product of at least secondary transfer, and possibly tertiary transfer. Furthermore, the palm and the palm face of the fingers have hardened skin which is also frequently washed, and therefore the human palm or palm-facing fingers are less likely than other areas of the body to shed significant quantities of epithelial cells anyhow.

IIRC, it was never shown that Sollecito's apparent DNA on the bra clasp was epithelial in origin (in contrast with Guede's DNA on/in Kercher which was definitively identified as being epithelial in origin). It's therefore reasonable to wonder whether this was sebaceous DNA, in which case it would likely have to have endured (at least) secondary transfer in order to arrive on the bra clasp. And while of course it's arguable that this secondary route might be Sollecito sebaceous fluid - Sollecito hand - bra clasp, it's clearly reasonable to suggest that the route might involve an extra hop and be something like: Sollecito sebaceous fluid - door handle or door face - incompetent crime scene investigator - bra clasp (tertiary transfer).
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You cannot identify where DNA comes from (at least not using typing techniques). Guede's DNA was attributed to epithelial DNA in the same way as Sollecito's. Technically sebaceous glands are epithelial in origin. To properly attribute DNA to epithelial origin you have to find epithelial cells on microscopy this was never done. It is not unreasonable to attribute DNA to being epithelial in origin so long as one is clear that urine, saliva, snot, as well as touch contain DNA of epithelial origin and the first three may not involve direct touch, all may involve secondary and greater transfer. Non epithelial DNA would be blood or sperm. This finding I do not find surprising as shed epithelials have undergone apotosis that destroys DNA. Trace DNA is hugely problematic.

ETA. People are always touching their faces, a big problem in disease transfer. One of the main benefits about masks in disease outbreaks is it stops people touching themselves. I suspect much touch DNA is transfer from face to hand to object.
 
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LondonJohn said:
Aaaand back to the topic of the thread!

One very interesting aspect of the recent academic paper on touch DNA co-authored by Vecchiotti is the contention that most low-template touch DNA is actually from sebaceous fluid (chiefly sweat) rather than epithelial skin cells. And that has interesting ramifications, since the human palm has no sebaceous glands and therefore cannot be the primary source of sebaceous DNA. And that in turn means that if sebaceous-origin touch DNA is found at, for example, a crime scene, then this must mean that it was either deposited by direct contact from a part of the body which does have sebaceous glands (e.g. the forearm or the chest or the face) or it was deposited by the hand via (at least) secondary transfer. And given that the vast majority of touch contact at anything like a crime scene is via hand contact, then this implies immediately that most low-template DNA found at the scene is likely the product of at least secondary transfer, and possibly tertiary transfer. Furthermore, the palm and the palm face of the fingers have hardened skin which is also frequently washed, and therefore the human palm or palm-facing fingers are less likely than other areas of the body to shed significant quantities of epithelial cells anyhow.

IIRC, it was never shown that Sollecito's apparent DNA on the bra clasp was epithelial in origin (in contrast with Guede's DNA on/in Kercher which was definitively identified as being epithelial in origin). It's therefore reasonable to wonder whether this was sebaceous DNA, in which case it would likely have to have endured (at least) secondary transfer in order to arrive on the bra clasp. And while of course it's arguable that this secondary route might be Sollecito sebaceous fluid - Sollecito hand - bra clasp, it's clearly reasonable to suggest that the route might involve an extra hop and be something like: Sollecito sebaceous fluid - door handle or door face - incompetent crime scene investigator - bra clasp (tertiary transfer).
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Nonsense. Have you never experienced a clammy handshake?
 
Vixen said:
Nonsense. Have you never experienced a clammy handshake?
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*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.
 
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