A Legal Study on the Seizure of Digital Evidence and the Handling of Irrelevant Information

With the widespread use of large-capacity data storage devices such as smartphones and the advancement of digital forensic technologies, it has become common practice for investigative agencies to create complete imaging files and then selectively extract relevant data during searches and seizures. Consequently, electronic data unrelated to the suspected offense is frequently collected alongside pertinent evidence. The Korean Supreme Court has recently ruled, in several cases including the D-NET decision, that the use of such unrelated data in subsequent, separate investigations constitutes an illegal practice. As a result, the legal obligation to delete, discard, or return unrelated data has emerged as a critical issue. This article analyzes the key legal issues identified in the D-NET ruling, particularly the illegality of using unrelated data for separate investigations. It further proposes that, despite the absence of explicit statutory provisions in the Criminal Procedure Act, the right to request the deletion of such data may be derived from existing rules on the return or provisional return of seized items. Additionally, this paper examines concrete methods for the return of unrelated data depending on the type of seizure conducted, as well as legal issues surrounding the use of storage devices that contain both related and unrelated data as admissible evidence.