Scout troopers, also known as biker scouts, were specially trained soldiers of the Imperial Stormtrooper Corps.
As light-armoured variants of the Imperial Stormtroopers, scout troopers were specifically trained for activities too complicated for regular infantry troopers. As such, they were exceptional additions to the Imperial Military as reconnaissance troops, spies and survivalists.
They were especially excellent marksmen, and thus they were regarded as the finest snipers in service to the Galactic Empire. Hence, they were particularly useful as assassins.