The question about why CN was charged and others weren't (specifically SS, AM & MH but also anyone else we haven't even heard about yet, if there are more) as accessory after the fact has been bugging a lot of us I think.
I think it just comes down to knowledge
Yes, in essence this is the distinction. To be an accessory after the fact of murder, the person must know that the one they are assisting has committed a murder (or at least, a homicide likely to be a murder). Although the others in DM's "entourage" have certainly known DM has committed crimes, there hasn't been any evidence so far that any of them had reason to believe DM had committed a murder (although if the LB and WM cases go to trial we may learn that some of these players did know or ought to have known). But CN's case is different in that she appears to have been directly involved in covering up the homicide itself and evidence concerning it, and (we may infer) knowing that it has taken place. The
knowledge is key, although it does not need to be accurate knowledge. Since DM was a habitual liar, he could and probably did tell her something quite different from the truth.Her testimony may clarify a lot of this.
Other instances of concealing information, evidence etc. were not in the context of the witness knowing that a murder had been committed; they were concealing evidence of crimes but not of homicide based on what they knew at that time.
Here's a good summary of the legalities involved:
https://en.wikibooks.org/wiki/Canadian_Criminal_Law/Offences/Accessory_After_the_Fact
I've been on the road for work and missed some of the nuances the last two weeks or so but have also wondered (as someone earlier mentioned) whether CN might have been driving the Yukon. I've tended to dismiss this since charges against her don't reflect that (she wasn't accused of being a party to the crime), but can't work out a scenario that fits the facts of the crime as we know them so far. I originally believed the shooting took place at the hayfield (when Tim likely got suspicious and may have tried to escape), but the video evidence suggests they didn't stop there long enough for any such struggle; OTOH, I can't imagine TB sitting placidly in the front seat following that obviously duplicitious move in going back to pick up the Yukon and having MS (presumably) drive it. Then, why the detour in Brantford? A lot of little things don't fit together. Unlikely we are going to get the whole story, either.