In this article, we analyze a residual-based a posteriori error estimates of the spatial errors for the semidiscrete local discontinuous Galerkin (LDG) method applied to the one-dimensional second-order wave equation. These error estimates are computationally simple and are obtained by solving a local steady problem with no boundary condition on each element. We apply the optimal L 2 error estimates and the superconvergence results of Part I of this work [Baccouch, Numer Methods Partial Differential Equations 30 (2014), 862-901] to prove that, for smooth solutions, these a posteriori LDG error estimates for the solution and its spatial derivative, at a fixed time, converge to the true spatial errors in the L 2 -norm under mesh refinement. The order of convergence is proved to be p + 3/2, when p-degree piecewise polynomials with p ≥ 1 are used. As a consequence, we prove that the LDG method combined with the a posteriori error estimation procedure yields both accurate error estimates and O(h p+3/2 ) superconvergent solutions. Our computational results show higher O(h p+2 ) convergence rate. We further prove that the global effectivity indices, for both the solution and its derivative, in the L 2 -norm converge to unity at O(h 1/2 ) rate while numerically they exhibit O(h 2 ) and O(h) rates, respectively. Numerical experiments are shown to validate the theoretical results.