I notice that in the media there's a constant reiteration of the fact that the use of the Buk missile system (about which I know nothing more than I read on a daily basis here and elsewhere) would require expert assistance from specialists in, or from, the Russian military. This is constantly quoted as undeniable evidence of direct Russian complicity in the act itself. Their ongoing supervision of the insurgency is a given whereas their direct participation is yet to be conclusively demonstrated.
As has been argued previously in this thread there are certain to be many people in Ukraine, especially the eastern Russian speaking region, who were or are current or former members of the Soviet, Russian or Ukrainian military. Amongst whom there are sure to be people trained in the use of this system.
Now I believe, as probably do the majority of spectators to this tragedy, that the evidence of culpability emerged very rapidly during the first few hours after the event, well before the various "interested parties" were able to start manipulating the news in order to serve their various agendas. So I find it very odd that all the politicos from the "victim" countries plus the USA keep insisting that the mere fact of the Buk system's use is de facto evidence of direct Russian participation in the missile's use. This is perfectly possible, quite obviously, but it seems to me to be very shaky as "evidence" and I'm puzzled as to why it's become so prominent.