Well correct those were my words. It was all my opinion ('jmo"), even the part that is confirmable in the pca but I'll go back and edit. According to the PCA there was no other dna on it. So he thought he did whatever he needed to in order to leave it clean
Moo
No other dna OBTAINED or FOUND - big difference. They only looked one place. That's actually recommended procedure (for many reasons). They can look more, but it requires consumptive testing. I know of no jurisdiction where that's allowed without a Judge's permission.
(Skip to the last part if this is too long)
The fact that they found DNA on the place most likely to contain DNA ended their search. It's like looking for anything else. Once you find it, you don't take up precious lab time and resources in testing more - unless asked or ordered to do so. That's not what the Defense is seeking, though.
Of course there's other DNA in leather. Bovine DNA for one - which of course, the Defense could say means a cow was involved in the murders. There's almost certainly DNA from some of the tanners (I won't go into the process, but there is very like either human or animal DNA besides bovine). No good forensic DNA is going to go immediately to a clearly mixed sample (the leather) when they have found an unmixed sample on the use point.
Testing the leather itself has indeed led to some silly arguments in some trials - just more to explain to the jury. But why doesn't the Defense want that? Because they already know that *breathing* deposits DNA on objects, and while BK was masked, he likely wasn't masked at every single moment that he handled that sheath. Even so, DNA is small. Very small. Wearing a mask diminishes but does not eliminate either COVID nor DNA from passing outside the mask.
So, I await their testing of the sheath, per judge's order - but it may never come. Because the Defense worries that it will just be more Kohberger DNA (and that the human DNA will be traced - by genetic genealogy aka ancestry study - to the locale where the sheath was made. As I understand it, that's in Mexico (where most of North America's leather tanning takes place). The profile from the workers would likely reveal that (just as in the JonBenet case, the "stranger DNA" fits with a Chinese male in a province where certain of JB's clothing items were manufactured). Dead end.
But complicates things. Why do that, if you're the State? And why risk showing the Jury that Kohberger touched more than just the sheath? Asking for *more* DNA on a criminal defendant is not good standard practice, IMO.
This is all just my opinion, too but there are reasons for these standards and I do not believe they ever tested the sheath in general. As I keep mentioning, that would require consumptive testing (taking a small amount of the top layer of the leather at the very least - it would mark/mar/change the evidence - that's against all forensic procedure). Merely swabbing it with something will not work because leather, unlike the snap, is porous and very unlikely to reveal results without a little scrape of the leather. Or at least, wet swabbing (which could be argued later removed valuable evidence - such as the color of the sheath). There's no evidence at all that LE or ISL went before a Judge to get permission. I do not believe any lab would do that without permission (and it's possible it was secretly given - in which case, it either turned up nothing, or the Defense knows that BK's DNA was found elsewhere on that sheath).
At some point in time, whoever handled that sheath got their finger oils into the leather - and that's not easy to clean. It's not a matter of wiping the sheath, the pores of the leather would need to be cleaned with a fluid - and I think such cleaning would be obvious, leave traces and simply point further to guilt. There's no evidence Kohberger did this. Surely he was paying attention in his classes when his profs told him that leather does not easily transfer DNA - as it absorbs it into its own DNA-bearing structure.
TL;DR Things that are made from DNA (leather) pose different problems in DNA analysis.
IMO.