If you give an item to a dead player, it will drop it on the ground (logical in my opinion). The problem is that no one is able to pick up this item except the dead player when he respawns.
After exploring the world save, I found that the EntityItem has the DataTag 'Owner' which value is the name of the concerned dead player. That Tag doesn't exist on items naturally dropped by the death of the player. And if you throw it manually, it has the DataTag 'Thrower' (with the same value) but can obviously be picked up by anyone.