Investigators looking into the downing of Malaysia Airlines Flight 17 face a series of unusually daunting challenges—from accessing the crash scene in the first place to taking possession of the plane's "black boxes"—that raise questions about whether any probe will be widely considered credible.
The crash site is in territory held by rebels, not controlled by the central government in Kiev. It is unclear the extent of cooperation between the two over access for international investigators who typically flock to the scene, sometimes within hours of a plane going down on land.