The primary goal of this research work is to detect and remove non responsive channels and trials in evoked potentials by tracing out the signals with very low energy. This is done by calculating the energy of the average evoked potential of each channel, and the energy of the average evoked potential of each trial. Then channel wise and trial wise median test is conducted to detect and remove non-responsive channels and trials. An attempt has been made to apply these techniques to 14-channel visual evoked potentials (VEPs) obtained from four different subjects.