  We show that if $X$ is an indecomposable $PD_3$-complex and $\pi_1(X) is the
fundamental group of a reduced finite graph of finite groups but is not
virtually cyclic then $X$ is orientable, the underlying graph is a tree, all
the edge groups are $Z/2Z$ and all but at most one of the vertex groups is
dihedral of order $2m$ with $m$ odd. Every such group is realized by some
$PD_3$-complex.
  We also propose a strategy for tackling the question of whether every
$PD_3$-complex has a finite covering space which is homotopy equivalent to a
closed orientable 3-manifold.
