  We study forward scattering of 2D massless Dirac electrons at Fermi energy
{\varepsilon} > 0 in single layer graphene through a 1D rectangular barrier of
height {u_0} in the presence of uniform Rashba spin-orbit coupling (of strength
{\lambda}). The role of the Klein paradox in graphene spintronics is thereby
exposed. It is shown that (1) For {\varepsilon} - 2{\lambda} < {u_0}<
{\varepsilon} + 2{\lambda} there is partial Klein tunneling, wherein the
transmission is bounded by 1 and, quite remarkably, for small {\lambda} >
{\lambda_0} {\approx} 0.1 meV, the transmission nearly vanishes when the
scattering energy equals the barrier height, {\varepsilon}={u_0}. (2) Spin
density and spin-current density are shown to be remarkably different than
these observables predicted in bulk single layer graphene. In particular, they
are sensitive to {\lambda} and {u_0}. (3) Spin current densities are space
dependent, implying the occurrence of non-zero spin torque density. Such a
system may serve as a graphene based spintronic device without the use of an
external magnetic field or magnetic materials.
