  We show a relationship between the non-acyclic Reidemeister torsion and a
zero of the acyclic Reidemeister torsion for a lambda-regular SU(2) or SL(2,
C)-representation of a knot group. Then we give a method to calculate the
non-acyclic Reidemeister torsion of a knot exterior. We calculate a new example
and investigate the behavior of the non-acyclic Reidemeister torsion associated
to a 2-bridge knot and SU(2)-representations of its knot group.
