  In the gauge-mediated supersymmetry breaking models with scalar tau as the
next-to-lightest supersymmetric particle, a scalar lepton may decay dominantly
into its superpartner, tau lepton, and the lightest scalar tau particle. We
give detailed formulas for the three-body decay amplitudes and the polarization
asymmetry of the outgoing tau lepton . We find that the tau polarizations are
sensitive to the model parameters such as the stau mixing angle, the neutralino
to slepton mass ratio and the neutralino mixing effect.
