  Majority of the A$_2$B$_3$ type chalcogenide systems with strong spin-orbit
coupling, like Bi$_2$Se$_3$, Bi$_2$Te$_3$ and Sb$_2$Te$_3$ etc., are
topological insulators. One important exception is Sb$_2$Se$_3$, where a
topological non-trivial phase was argued to be possible under ambient
conditions, but such a phase could be detected to exist only under pressure. In
this Letter, we show that like Bi$_2$Se$_3$, Sb$_2$Se$_3$, displays generation
of highly spin-polarized current under mesoscopic superconducting point
contacts as measured by point contact Andreev reflection spectroscopy. In
addition, we observe a large negative and anisotropic magnetoresistance in
Sb$_2$Se$_3$, when the field is rotated in the basal plane. However, unlike in
Bi$_2$Se$_3$, in case of Sb$_2$Se$_3$ a prominent quasiparticle interference
(QPI) pattern around the defects could be obtained in STM conductance imaging.
Thus, our experiments indicate that Sb$_2$Se$_3$ is a regular band insulator
under ambient conditions, but due to it's high spin-orbit coupling, non-trivial
spin-texture exists on the surface and the system could be on the verge of a
topological insulator phase.
