If, as has been suggested an SA-11 missile downed MH-17 then it is unlikely to be a case of mistaken identity as the buk missile launcher used for the deployment of the SA-11 has an IFF (identify friend or foe) to determine the type of aircraft.
It will be nigh on impossible to prove it was not a mistake, it will be difficult enough to prove who did what. It is also extremely unlikely (and again unprovable) that it was a deliberate attack knowing it was a civillian plane (which side has anything to gain by this).
So again, it is a plane flying over a warzone, it get's shot down.
What's the point of an investigation, what usefull result will it give us.