  A natural consequence of the composite operator propagator-vertex description
of deep inelastic scattering developed by the authors is that the anomalous
suppression observed in the flavour singlet contribution to the first moment of
the polarised proton structure function $g_1^p$ (the `proton spin' problem) is
not a special property of the proton structure but is a target independent
effect which can be related to an anomalous suppression in the QCD topological
susceptibility. In this paper, it is shown how this target independent
mechanism can be tested in semi-inclusive deep inelastic scattering in which a
pion or D meson carrying a large target energy fraction $z$ is detected in the
target fragmentation region.
