The determination of the CP-violating phase phi_s in Bs0 -> Jpsi phi decays is one of the key goals of the LHCb experiment. Its value is predicted to be very small in the Standard Model but can be significantly enhanced in many models of new physics. We will present a detailed breakdown of the phi_s analysis using 37pb^-1 of pp collisions at sqrt(s) = 7 TeV collected by LHCb in 2010. We find phi_s in [-2.7, -0.5] radians @ 68% CL. In addition, we discuss prospects for the phi_s measurement with 2011 data and highlight decay modes which can be used to enhance our understanding of CP-violation in Bs0 mixing.
