In 1983, Supreme Court ruled that policemen could not testify to the defendant's confess when the defendant objected. The Court reasoned that since the Code of Criminal Procedure denied the admissibility of the documents which was made by the police and contained the defendant's confess when the defendant object, the policeman was not allowed to testify to that effect, either. The Code of Criminal Procedure, however, does not explicitly prohibit the use of such testimony. As for the document which contains the confess of the defendant, it is extremely difficult to contest. Because the defendant cannot cross-exam the policeman who interrogated the defendant or the defendant himself. But as for the testimony, the reliability can be guaranteed by the cross-examination. In addition, such testimony often includes first-handed, accurate information and cannot be obtained otherwise. This study is an attempt to illustrate such an occasion. In this case which was ruled in 2005, Supreme Court once again denied the admissibility of the interrogator's testimony. However there are some special elements to be considered. Here, the policeman met the defendant near the crime scene just after he had committed homicide; the setting was not interrogatory; the defendant freely admitted that he had killed the victim. If he had met a civilian, he would have told the same story. In situation like this, there is no danger of misconception, manipulation, or memory lapse. This case clearly shows that under certain circumstance it is necessary, sometimes desirable to admit interrogators' testimony. In conclusion, the admissibility of the policeman's testimony should not be decided uniformly. Rather, it should be decided case by case in the light of reliability.