This study compares the mediation aspects of three interpreters at a cross-examination in criminal trial with the aim of observing how the different educational backgrounds of the interpreters affect the proceedings in trial. Judicial interpretation education programs were offered within the nation in a variety of ways due to awareness of the importance of judicial interpretation. Among the three interpreters, interpreter 1 and interpreter 2 had completed the judicial interpretation education program while interpreter 3 had not taken part in the said education program. The study conducts a discourse analysis to measure the mediation aspects of three interpreters during court interpreting. First, the number of questions asked are quantitatively analyzed to measure the intervention of the interpreter. Then factors such as ‘additional questions’, ‘use of third person’, ‘explanation’, ‘communicative coordination’ are considered for inductive deduction in order to measure the mediation aspect of the interpreter. As a result, it was confirmed that interpreter 3 was giving too many additional questions, thereby affecting the proceeding of the trial.