  Non-local currents and voltages are better able at withstanding the
deleterious effects of dephasing than local currents and voltages in nanoscale
systems. This hypothesis is known to be true in quantum Hall set-ups. We test
this hypothesis in a four terminal quantum spin Hall set up wherein we compare
the local resistance measurement with the non-local one. In addition to
inelastic scattering induced dephasing we also test resilience of the
resistance measurements in the aforesaid set-ups to disorder and spin-flip
scattering. We find the axiom that non-local resistance is less affected by the
detrimental effects of disorder and dephasing to be in general untrue for
quantum spin Hall case. This has important consequences since it has been
widely communicated that non-local transport through edge channels in
topological insulators will have potential applications in low power
information processing.
