  We calculate exact analytical expressions for \oas 3-jet and \oasz \\ 4-jet
cross sections in polarized deep inelastic lepton nucleon scattering.
Introducing an invariant jet definition scheme, we present differential
distributions of 3- and 4-jet cross sections in the basic kinematical variables
$x$ and $W^2$ as well as total jet cross sections and show their dependence on
the chosen spin-dependent (polarized) parton distributions. Noticebly
differences in the predictions are found for the two extreme choices, i.e. a
large negative sea-quark density or a large positive gluon density. Therefore,
it may be possible to discriminate between different parametrizations of
polarized parton densities, and hence between the different physical pictures
of the proton spin underlying these parametrizations.
