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, and LE being able to prove who knew what, and when. I think with SS, AM and MH it certainly seems like they had to have known more details than they've let on, but it's also entirely possible they didn't actually have knowledge that DM and MS shot Tim and stole his truck. If you think about it, from their perspectives (DM's entourage), there was no legitimate reason for them to assume DM was connected to the missing guy on the news (even if they had already heard about it, despite some of them claiming they hadn't), because for all they knew, he was just a thief, not a killer. So at least at the beginning they probably didn't make the connection - until more details started coming out.
I don't believe for a moment though, that MH and AM didn't talk about what was in the tool box, or what was in the back pack, or that at least one if not both of them didn't actually look IN the backpack. It does sound reasonably truthful that they really didn't know DM killed a man and stole his truck (although we've heard AM did know in advance he was planning on stealing a truck) until they got together and started talking and piecing it together. MS acting all sketchy, DM meeting MH at 4am, sending the back pack off with one guy and the toolbox off with another, etc. It's possible MH really did think it was just drugs in the toolbox as he'd seen before. Until the pieces started falling into place, that is.
I think with the exhaustive investigation from LE on this case, if they were able to confirm/prove any of these guys had knowledge of what DM (and MS) did in Ancaster that night, and helped him in an attempt to avoid being caught or being prosecuted for it, they most definitely would have been charged the same way CN was.
100% speculation & moo