  Tests of CP violation by appropriate momentum correlations in $Z\to 3$ jets
and in particular in $Z\to b\bar bX$ probe CP-violating effective couplings --
that manifest themselves as form factors -- which conserve the quark chirality
and quark flavour. By giving two examples we show that such couplings can be
induced at one-loop order in extensions of the Standard Model with CP violation
beyond the Kobayashi-Maskawa phase. In one of the models we compute the
chirality-conserving part of the CP-violating $Zb{\bar b}$-gluon amplitude for
massless $b$ quarks, determine the resulting effective dimension $d=6$
couplings in the local limit, and discuss the possible size of the effects.
Finally we show that in models with excited quarks the chiral-invariant
CP-violating effective interactions could be quite large if appropriate
couplings are of a size characteristic of a strong interaction
