North_Idaho_Nony
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Thanks so much for this excellent explanation!Everyone was asleep except Xana, apparently. No one heard anything. Murphy the Dog may have growled (misinterpreted as playful growling by one of the surviving roommates). There was no chaos.
It was fast, gruesome and silent. No one alerted to anything. People inside the house would not have seen the blood right away (there's some on the outside of the house - and there are latent bloody footprints from someone coming down the stairs - but no mention of pooled blood inside the house. Latent means "invisible."
The bloody footprints belong to a person who appears to be the intruder - a single person's footprints. I think we'd have heard if there were two sets and LE would be looking for that other person. In order to produce bloody footprints, someone had to step in blood, for sure.
There is no such thing as indirect DNA. Every cell in an organism has "direct" DNA. It has only one form and is created in only one set of processes (cellular division). Sweat is not indirect. It's a body fluid. Body fluids like semen and sweat are not indirect. The would make rape kids "indirect," but I've never heard anyone say that. It's likely epithelial DNA, given where it was found. Doesn't matter the type of cell from which it came. DNA is DNA.
It was not even what is sometimes called "trace" DNA (that has an entirely different meaning in forensic science). It is "touch" DNA (an encounter between the body and an object which leaves a DNA trace of that person being very near or touching the object - there is now research on exhaled DNA as well. Epithelial DNA is by far the most common type of forensic DNA that's found.
"Touch" merely refers to the method by which the DNA got where it is. We don't say "touch fingerprints", DNA comes with fingers as well. Even after death, humans are shedding/discarding some DNA. DNA persists for centuries, even millennia, in some cases. DNA can be obtained through indirect methods of analysis - which would be much harder to explain to a jury. There's no evidence that any of these reconstructive methods were used in this case.
I believe BK used tactics that were specifically designed to keep himself from being bloody - the technique I've described (unlike throat slashing) does not produce external blood spurts - but there would have been blood, for sure. He wore a mask, suitable clothing and gloves. He had prepared his car to receive those items, just in case he was stopped (we know of three traffic errors resulting in stops for him - I don't think he's a great driver).
I'm going with "he took precautions and wasn't bloody" when he climbed back into the driver's seat of his car. No victim DNA was found inside his vehicle (that's according to AT though).
He did exactly what all forensic specialists know to do to keep their own DNA out of a crime scene (this is usually learned at the bachelor's level in criminal justice, a doctoral candidate in criminology would know this and should be prepared to explain and TEACH it, criminologists are hired as consultants by LE agencies to review, do and establish such training). It's an area of specialization, however (no grad student would be hired in such a capacity - and they'd need more than grad criminology coursework in the forensic anthropology/genetics to get to that level of expertise). I have tagged along and suited up to make sure my own DNA didn't contaminate a crime scene (they still take samples of all forensic personnel and visitors to crime scenes if there's good local LE practice - you can find videos of the Moscow PD forensic investigators suiting up - including the crime scene photographers). I've been to a body farm and suited up there for the same reason (as the whole point of my field trip was to observe various field DNA collection techniques).
BK did very well, so far as we know, at keeping his DNA off objects - as I hope I did when I did the above things. BK used his training as a criminal justice and budding criminologist to aid in planning this crime - to me, it almost HAS to be someone with extensive knowledge of how to avoid forensic detection. A student of crime plans a crime - this is what it looks like. I also think his VSS plays a role in learning to plan things carefully and adjust for variables that the rest of us might find nerve-wracking.
I would love to see an academic citation or two describing what, exactly "touch DNA" is (other than a popular notion). Here is an article where it is mentioned, but in quotation marks (because it is not proper scientific terminology). Note that the author uses the word "trace" to mean the same thing. That's how it was usually referred to until the press started using other terms. But the press are not DNA experts.
And here is example of how the term is currently used in science (to mean epithelial DNA):
Some view any sample gained with a swab to be "touch" DNA (which makes sense, as shorthand). Note that there's high scientific validity to what scientists are calling touch/epithelial DNA. I am at a loss as to why anyone (including journalists) think that epithelial DNA is problematic. But then, some people thought fingerprints were problematic. The media has decided "touch" DNA is a specific forensic problem - but that's wildly inaccurate.
IMO.
So many here know so much more about DNA evidence than I do, and I’ve always been puzzled by the references to “touch DNA” as being somehow inferior or problematic.
LE routinely uses buccal swabs to collect epithelial cells for DNA purposes, so the concerns about the epithelial “touch DNA” in the groves of the knife sheath snap that subsequently matched the BK’s directly collected DNA made me feel like I was missing something.
Thanks to your excellent tutorial, I now understand I wasn’t missing anything after all.
ETA: “DNA is DNA.”