I think he was clued in on the whole thing from Voldemort
. Out of all the servants I do think Voldy did trust Snape
with a lot of info. I am trying to remember the chapter where it discussed everything regading Snape
. It seemed ot pretty much say that Snape
in on the plan for his death. I remember them discussing the fact that Snape
should do the deed if need be because he didn't want Draco to be a murderer.