  The production of pions emitted backward in inelastic neutrino-nucleus
interactions is analyzed within the impulse approximation in the framework of
the dual parton model. We focus on the $Q^2$-dependence of the multiplicity of
negative pions, normalized to the total cross section of the reaction $\nu + A
\to \mu + X$. The inclusion of planar (one-Reggeon exchange) and cylindrical
(one-Pomeron exchange) graphs leads to a multiplicity that decreases as $Q^2$
increases, in agreement with recent measurements carried out at CERN by the
NOMAD collaboration. A realistic treatment of the high momentum tail of the
nucleon distribution in a nucleus also allows for a satisfactory description of
the semi-inclusive spectrum of backward pions.
