  According to the basic properties of QCD, colour reconnection effects can
occur in hadronic processes at high energies. The comparison of $e^{+}e^{-}\to
Z^0Z^0\to q\bar{q}q'\bar{q'}$ events with the superposition of $Z^0\to
q\bar{q}$ and $Z^0\to q'\bar{q'}$ events from LEP1 would provide an unambiguous
model-independent probe. We show that at LEP2 energy, the background processes
are negligible if we select only $e^{+}e^{-}\to Z^0Z^0\to b \bar{b}c\bar{c}$
events, and limit the measurements in the phase space of on-shell $Z^0Z^0$
events.
