  In the CP-invariant supersymmetric theories, the steep S-wave (slow P-wave)
rise of the cross section for any non-diagonal neutralino pair production in
$e^+ e^-$ annihilation, $e^+e^- \to \tilde{\chi}^0_i \tilde{\chi}^0_j$ ($i \neq
j$), near threshold is accompanied by the slow P-wave (steep S-wave) decrease
of the fermion invariant mass distribution of the 3-body neutralino decay,
$\tilde{\chi}^0_i \to \tilde{\chi}^0_j f\bar{f}$ ($f=l$ or $q$), near the end
point. These selection rules, unique to the neutralino system due to its
Majorana nature, guarantee that the observation of simultaneous sharp S-wave
excitations of the production cross section near threshold and the lepton and
quark invariant mass distribution near the end point is a qualitative,
unambiguous evidence for CP violation in the neutralino system.
