We consider the dynamics of a particle of mass M and spin J in AdS 3 . The study reveals the presence of different dynamical sectors depending on the relative values of M , J and the AdS 3 radius R . For the subcritical M 2 R 2 − J 2 > 0 and supercritical M 2 R 2 − J 2 < 0 cases, it is seen that the equations of motion give the geodesics of AdS 3 . For the critical case M 2 R 2 = J 2 there exist extra gauge transformations which further reduce the physical degrees of freedom, and the motion corresponds to the geodesics of AdS 2 . This result should be useful in the holographic interpretation of the entanglement entropy for two-dimensional conformal field theories with gravitational anomalies.