  Spin currents are key to spin torque devices, but determining the proper spin
current is non-trivial. Here we derive a general quantum-mechanical formula for
the intrinsic proper spin current showing that it is topological and can be
finite in the gap. For topological insulators with an out of plane
magnetization and the chemical potential in the surface state gap, the net spin
torque is determined by the competition between the topological spin-Hall
torque due to the bulk and the topological Edelstein effect due to the surface
states. We also discuss spin-3/2 hole quantum wells.
