  We consider the frustrated antiferromagnetic s=1 Heisenberg quantum spin
chain with regard to the Marshall-Peierls sign rule (MPSR). By using exact
diagonalization data we investigate the breakdown of the MPSR in dependence on
frustration and compare our findings with data for s=1/2. We calculate a
critical value of frustration J_2(crit) where the MPSR is violated. The
extrapolation of this value to the infinite chain limit holds J_2(crit) approx.
0.016, lower than in the case of s=1/2 (J_2(crit) approx. 0.027). This points
to a stronger influence of frustration in the case of s=1. Nevertheless the
calculation of the weight of the Ising-states violating the MPSR shows that the
MPSR holds approximately even for quite large frustration and may be used for
numerical techniques.
