Would you be willing to expound on that or direct me to where you have previously detailed that theory?
[Link]This is where I strongly disagree with you. The scene of the accident is described as Harry having been hit in the back of the car. So if there was actual damage to the back of the car, that isn't a fake accident.
I seem to recall Murph or Harry noting that they couldn't tell if there was any new damage.
Could be wrong, though.
Now, back onto the topic of Cowl:
Yes, someone working with Justin who already knew about the Word of Kemmler existing inside the skull could have deduced that Dresden would have the skull.
I guess.
I still think that the textual Doylist cluebat is the big deal breaker. Harry spends a lot of time flashing back to Justin in this book. I don't think that's typical, and it's not really THAT relevant to the plot. Flashing back to Harry meeting BOB, sure, and flashbacks with Bob and Justin, sure, but we don't get those.
So there's that. Plus mentioning Harry's dead mentor in the big necromancy book and pointing out that Justin was the disciple of a powerful necromancer and had that guy's notes... Lots of clues that Justin isn't D-E-D dead in the book that introduces Cowl.
(As for where Kumori is during White Night... Elaine is in White Night and Cowl is preying on her people. Maybe Kumori has reformed?)