In this work a method is established for isolating effects due to single or successive two-body scatterings from those arising from three-body coupling in a three-particle Coulomb system above the complete breakup threshold. It is shown that three-body interactions decide the weighting of individual scattering amplitudes, and hence, determined the interference pattern of these amplitudes. In addition, the method is applied to the analysis of low-energy, electron-impact ionization of atomic hydrogen in the coplanar asymmetric energy-sharing kinematic. The ionization dynamic leading to the measured cross section is unraveled. It is demonstrated that, unlike the situation at higher energies, at low incident energies the cross section is largely decided by interferences indicating a strong three-body coupling.