I don’t know that I have a specific source. But the fact that apparently all traces of biological evidence seem to have been removed - save one small area pointing to a certain suspect perhaps might lead one to conclude similarly? And I am fairly certain I have read many times in published sources the past many months and years….. that the sheath was thought to have been cleaned? But if there are any posts in the circa 101 BK threads on this I will not be able to find them.
Maybe not the best source but this New York Post online February 8, 2023 article by Patrick Reilly entitled ‘Accused Idaho murderer Bryan Kohberger may have left knife sheath behind to mislead investigators: expert’:
“If you took a pistol out of your holster, wouldn’t you put it back in?” asked John Kelly, a psychotherapist who has interviewed serial killers.
nypost.com
Excerpt from that article: “The sheath - which was found in bed with two of the four victims - could have been left behind purposefully after it was thoroughly wiped down, Kelly said.” (NB: per the article Kelly is John Kelly, a psychotherapist who was interviewed serial killers.)
Perhaps the perpetrator thought in their mind that they might have cleaned the knife sheath ‘forensically’. At least well enough to avoid incriminating evidence? My further suspicion is that evidence of some sort of ‘cleaning’, whether ‘forensically’ or the like - if an assailant had carried a knife in sheath to a crime scene…… and then separated them for use, it seems reasonable to conclude they might have left more evidence on it? Aside from the tiny amount supposedly use to make a genealogical link to the now charged suspect. MOO