Ghostwheel
Pyrrhonist
To be fair, no, we don't. We know that BKs DNA is on the sheath found next to one of the murdered people. It could have belonged to Murphy, for all we know, though he'd have had a hard time wiping his paw prints off it. But BK touched it at some point where it did not get covered or wiped off.We know whose knife sheath it was.
Having no reason or excuse for his DNA being on a sheath found next to a murdered person, this becomes circumstantial evidence 1.
2 is cell phone data indicating his cell phone went to the area of the house several times before the murders.
3 is a car like his having left his apartment parking lot,, being caught on multiple cameras and then in the vicinity during the crime, making 3 passes of the house before stopping on the fourth pass.
4 is the car leaving at 4:20 and his phone reactivation at 4:50 near Blaine which is about the correct time for travel that far.
5 is his driving back to the area around 9 am before any crime was announced (why would he go there? No stars to gaze at in the daytime.)
6 having pinged in Moscow on several occasions before the murders, the cell phone never pinged there after the murders.
7 is putting his trash in a neighbors trash can
I could go on, and there is much more circumstantial evidence we don't know about. None of these things alone point to a person being a murderer. LE believes that everything they have together does point that direction. I can believe variations of someone stole the knife and sheath or carefully had BK touch the sheath and then planted it at the scene to throw suspicion on BK, or that the DNA was left by the killer, or something in between. Adding up known circumstantial evidence points to BK barring some valid reason his DNA was on a knife sheath next to a murder victim.
I will be quite interested to see what else LE has.