2+1 dimensional topological insulator described by the Kane-Mele model in the
presence of Rashba spin-orbit interaction is considered. The effective action
of the external fields coupled to electromagnetic and spin degrees of freedom
is accomplished within this model. The Hamiltonian methods are adopted to
provide the coefficients appearing in the action. It is demonstrated
straightforwardly that the coefficients of the Chern-Simons terms are given by
the first Chern number attained through the related non-Abelian Berry gauge
field. The effective theory which we obtain is in accord with the existence of
the spin Hall phase where the value of the spin Hall conductivity is very close
to the quantized one.Comment: 15 pages, 1 figure. Comments and refs adde