One part of the paintbrush was probably used for the sexualt assault and is missing and the other part for the garrote and the third part is in the tray having P's red fibers . This shows If the garrote was pure staging, then the one making it was aware that the other part of it were used for assaulting JB so she/he chose exactly that particular stick among tens of brushes.
But how did the stager know that the perpetrator put the paintbrush inside JB? The birefringent material if that came from the paintbrush were discovered at the autopsy report and were not visible .
So either the bloodied part of the brush was left on the scene or the perpetrator confessed that or maybe the garrote was not staging and the assaulter and the one who did the garrote are the same person.
MURDERER_SERVANT,
This is I think the best explanation. Its a bit like the days before we saw the True Bills, i.e. BDI was the least inconsistent theory, so explained most of the evidence.
It looks like JonBenet was assaulted with the paintbrush. This might have been deliberate staging or some kind of sexual assault linked to JonBenet's death, I tend to the latter?
Along come the parents to
tidy up and they wipe JonBenet down, pull up her size-12's, and use the paintbrush as staging, but remove one end?
Corroboration here lies in the fact that a piece of the paintbrush is still
missing, why remove it if you intend it to be part of some kind of staging?
There is the possibility that it was left inside JonBenet, and this is why Coroner Meyer refers to
birefringent material and say not cellulose splinter?
So Patsy knows JonBenet was sexually assaulted, she or JR wiped her down hoping to hide this?
Was the paintbrush added to the ligature to explain away its presence, did the parents know there was a
missing piece, so concluded the obvious from the blood stains on JonBenet's inner thighs?
ETA: Patently JonBenet's killer might have used the paintbrush and ligature in some other capacity, prior to killing JonBenet and defiling her?
When the parents arrive they have a
incomplete paintbrush, a ligature and a blood stained JonBenet.
.