2. Article 199(1) of the Criminal Procedure Act explicitly states the principle of voluntary investigation.

The act of accompanying a suspect to an investigative agency, etc. in the form of obtaining consent from an investigator in the course of an investigation does not have any means to restrain the physical freedom of the suspect even though it is substantially similar to the arrest and detention, so it is not systematic and practical to guarantee the voluntariness as well as institutionally. Moreover, there is a high possibility that the Constitutional Act and the Criminal Procedure Act do not provide various rights guarantee devices to the suspect who is arrested or detained on the ground that it is prior to the regular stage of arrest and detention.

Therefore, it is reasonable to view that the legality of the accompanying is recognized only in cases where it is proved by objective circumstances that the investigator was carried out by the voluntary will of the suspect solely, such as where the investigator knew that he/she could refuse the accompanying to the suspect prior to the accompanying, or the suspect who was accompanied could freely leave the accompanying place or at any time.

(2) Article 308-2 of the Criminal Procedure Act provides that “Any evidence obtained in breach of the due process shall not be admitted as evidence” (see, e.g., Supreme Court Decisions 2009Do6717, Jun. 30, 2011; 2012Do8890, Sept. 13, 2012). In addition, Article 308-2 of the Criminal Procedure Act provides that “Any evidence obtained in breach of the due process shall not be admitted as evidence for conviction” (see, e.g., Supreme Court Decisions 2009Do6717, Jun. 30, 2