Respectfully, we don't know if the sheath actually housed the actual murder weapon either. For that matter we don't even know if it really was a kbar knife that was used in the crime either.
This is true. However, I do believe there's a reason that the Defense has not tried to argue that the sheath isn't related to the murder weapon.
And that's because the autopsy reports (which we do not have but which certainly exist) show that a Ka-Bar style knife was used.
It's also possible to use forensic MRI and other techniques to state definitively that it was a KaBar knife (which I sure hope has been done). KaBar uses a proprietary coating on its knives and the chemical structure can be analyzed by using any existing KaBar knife of the type that goes with the sheath. Then, swab the wounds and look for forensic metal traces (aided if necessary by MRI).
So of course we don't "know" it, but if in fact the autopsies show it was a different size and style of knife, I don't think BK would behind bars right now - and I think the Defense would have argued vigorously to get that huge problem in front of the Judge. Instead, I have to believe the autopsies show knife wounds consist with the type of knife that goes with that sheath.
IMO. I have patience mode on, because I know there are many similar issues that the Defense could still bring in pre-trial motions. The Judge has to collect their actual list of evidentiary items and witnesses, and then the two sides will argue about various pieces of each others' evidence. In the meantime, to me Occam's razor says that the sheath matches the knife used to produce the wounds of four people. The size and shape of the knife blade is known and there could be more forensic evidence (which the Defense already knows) that is incriminating.
So my question is this, this is a handmade item, so why wouldn't the DNA of the person or people who made it also be on the sheath? AND wouldn't someone who installed the snap or in quality control have opened and closed it to make sure it worked?
I wouldn't call it handmade. Somewhere on youtubes there are videos about the tanning process and sheath making manufacture (maybe even one from KaBar). It's assembly line work. The tanning process itself involves big vats of acidic materials. There will be human and bovine DNA (mostly bovine) in that vat.
The snap is very likely installed by a machine (I have a hand version of a snap installer - I am pretty sure that KaBar uses the industrial ones - it's like a big stamping machine). A worker (gloved and usually wearing a hat for safety reasons) holds the sheath part under the stamping machine. Later, the two halves are sewn together on giant sewing machines with workers wearing safety gear (I'm thinking they probably have visors - because while it's unlikely, big sewing machines can throw parts).
I am guessing that the snap is simply closed together (by a uniformed, probably UNgloved worker) right before it goes into the packaging array. No one is opening and shutting the snap over and over. In order for DNA to get down into that snap groove, a person would probably have to use it several times. As we use things, the microscopic DNA drifts down into the nooks and crannies of what we're using. The person who sewed the sheath probably left DNA elsewhere on the sheath.
And, of course, my view is supported by the evidence. Only one person's DNA was found inside that snap. If other people had used the snap, yes, there could (or would be, depending on how many times) some other person's DNA on the sheath.
Which there wasn't.
Here is a video of a Mexican tanning operation:
As you can see it's high tech and the machines are gigantic.
Most videos of sheath sewing are by amateurs - but there are a couple showing industrial process (and no one is wearing gloves when they sew - they need exquisite tactile control to get those stitches so even). I figure that at some point, a human likely touched that snap in the process (a worker) but that the knife is cleaned and wiped before packaging - and that the worker only touches it briefly (as they load the bits into the stamping machine?)
That's why I think it's likely that there's stranger DNA elsewhere on that sheath.
IMO.
