  I present in this paper the neutron spin physics program in Hall A at
Jefferson Laboratory using a polarized helium-3 target. The program encompasses
several completed experiments, in which, valuable spin observables (spin
dependent structure functions) were measured in order to learn about how the
nucleon spin arises from the behavior of the constituents. These experiments
also offer a ground for testing our understanding of the strong regime of
quantum chromodynamics (QCD) the theory of strong interactions through the
determination of moments of these structure functions.
