  We discuss the importance of inelasticity in the P-wave pi pi amplitude on
the Dalitz distribution of 3pi events in J/psi decay. The inelasticity, which
becomes sizable for pi pi masses above 1.4 GeV, is attributed to
  KK to pi pi rescattering. We construct an analytical model for the
two-channel scattering amplitude and use it to solve the dispersion relation
for the isobar amplitudes that parametrize the J/psi decay. We present
comparisons between theoretical predictions for the Dalitz distribution of 3pi
events with available experimental data.
