The fluctuation theorem gives an analytic expression for the probability, in a nonequilibrium system of finite size observed for a finite time, that the dissipative flux will flow in the reverse direction to that required by the second law of thermodynamics. In the present paper a local version of the fluctuation theorem (LFT) is derived heuristically. We find that in the case of planar Poiseuille flow of a Newtonian fluid between thermostated walls, nonequilibrium molecular dynamics simulation results support our proposed LFT.