  We study the final state interaction in 3-pion decay of meson resonances at
the Excited Baryon Analysis Center (EBAC) of JLab. We apply the dynamical
coupled-channels formulation which has been extensively used by EBAC to extract
N* information. The formulation satisfies the 3-pion unitarity condition which
has been missed in the existing works with the isobar models. We report the
effect of the 3-pion unitarity on the meson resonance pole positions and Dalitz
plot.
