수사기관의 현장대화녹음에 관한 검토 ― 대법원 2024. 5. 30. 선고 2020도9370 판결 ―

The case under review concerns the admissibility of evidence obtained when investigative authorities, acting undercover, secretly recorded on-site conversations during an investigation into prostitution solicitation. While the appellate court found the recordings to violate due process, the Supreme Court held that they were lawfully obtained and presented the first explicit criteria for assessing the legality of on-site conversation recordings. A central issue is whether such recordings constitute voluntary or compulsory investigations. Although the substantive approach has been dominant, classifying on-site conversation recordings as voluntary investigations under the formal view better ensures legal stability in accordance with the principle of statutory control over compulsory measures, while still reflecting investigative realities. Even voluntary investigations, however, must satisfy requirements of necessity, reasonableness, and procedural propriety. Whether the recordings constitute testimonial evidence depends on their connection to the facts to be proven. In this case, the recordings served to show the existence of the criminal situation rather than the truth of the statements’ content, thereby placing them within the category of non-testimonial evidence, similar to on-site video or audio recordings. The Supreme Court applied standards parallel to those used for evaluating the legality of on-site visual recordings: contemporaneity with the criminal act, necessity and urgency of preserving evidence, and the use of reasonable methods. Yet the latter two criteria remain abstract. This paper refines the criteria by linking “necessity and urgency” to established concepts in criminal procedure and by subdividing “reasonableness” into factors such as the manner of entry, scope and content of the recording, location, and timing. In addition, the paper highlights the broader institutional implications of adopting a more structured framework for assessing the legality of covert on-site recordings. By articulating clearer safeguards and investigative boundaries, the proposed criteria help prevent excessive encroachment on individual rights while offering investigators a more predictable and legally coherent standard. This balance is essential in areas where covert investigative techniques are frequently employed but remain insufficiently regulated by statute or precedent. These refinements aim to provide clearer guidance to investigative authorities and prevent disproportionate infringement of individual rights while maintaining investigative effectiveness.