Define multiple blunt impact trauma; does one always die from this?

No. Multiple blunt impact trauma means just what it says: more than one hit from something blunt. It does not speak to the magnitude of the blows, so this may or may not cause death.
Blunt trauma. Death can occur from blunt trauma if it is severe enough like head trauma or cardiac trauma . Blunt trauma can lead to internal bleeding from ruptured or damaged organs and that to cam lead to death if excessive.
Blunt trauma - die? Any mod to severe blunt trauma to different part of either the abdomen or chest - severe internal system organ injuries can result and has a very high mortality to it (dying).