Whether Printing Documents and Copying Files Without Regard to Relevance to the Suspected Offence in the Search and Seizure of Electronic Information Violates the Warrant Requirement: Standards for Excluding Illegally Obtained Evidence

The Origin of the Case and the Core Legal Question

Supreme Court Judgment 2020Do10908 rendered August 14, 2025 (Leakage of Military Secrets, Obstruction of Exercise of Rights by Abuse of Authority, and Disclosure of Official Secrets [a case in which a separate offence was discovered, and prosecuted, in the course of examining electronic information stored on a mobile phone that had been printed out in bulk in the form of an Excel file]) squarely addresses the following question: does printing out electronic information from a copy taken to the investigative agency's office, without distinguishing relevance to the suspected offence, constitute an unlawful seizure, and is derivative evidence based on it inadmissible?

The Supreme Court's core conclusions may be summarised as follows. The Supreme Court held that printing out or copying from a copy taken off-site without distinguishing relevance is, in principle, an unlawful seizure contrary to the warrant requirement principle. It further held that derivative evidence obtained on the basis of illegally collected evidence likewise cannot, in principle, be used as evidence to find guilt, and that such evidence is inadmissible where it does not fall within an exception to the exclusionary rule for illegally obtained evidence and the causal link between the seizure procedure and the collection of the derivative evidence cannot be regarded as attenuated or severed. The operative part reads: "The part of the judgment below convicting the defendant (including the part acquitted in the reasoning) is reversed, and this part of the case is transferred to the Seoul High Court. The Military Prosecutor's appeal is dismissed." The judgment's mode of adjudication is that of setting out requirements (following existing precedent).

This analysis follows the structure of the issues and the standards of judgment shown in the published judgment, and examines why the lower court and the Supreme Court diverged in their readings of the same record.

Sources for this section: Supreme Court Judgment 2020Do10908 rendered August 14, 2025 — Official text of the judgment, National Law Information Center

The Structure of the Issues Set by the Summary of Holdings and the Referenced Provisions

The framework of the summary of holdings as set out in the judgment is as follows. [1] The exceptional cases in which, in a search and seizure of electronic information by an investigative agency, it is permissible to take the storage medium itself or a copy of it off-site, such as to the investigative agency's office / Whether printing out as documents, or copying as files, electronic information arbitrarily stored on a storage medium or copy taken to the investigative agency's office or elsewhere, without distinguishing relevance to the suspected offence, constitutes an unlawful seizure contrary to the warrant requirement principle (affirmative, in principle) [2] Whether evidence collected by an investigative agency without following the procedures prescribed by the Constitution of the Republic of Korea and the Military Court Act, and derivative evidence obtained on the basis of such evidence, may be used as evidence to find guilt (negative, in principle), and the exceptional cases in which a court may use such evidence to find guilt / Matters a court must consider when finally determining the admissibility of derivative evidence [3] A case holding that, where a Military Prosecutor of the Special Investigation Unit on the Defense Security Command allegations obtained a warrant for search, seizure and inspection concerning A's alleged conspiracy to commit insurrection, etc., seized the mobile phone of the defendant, who had been a witness in relation to the offence concerned, and created a copy of it; then, while analysing an Excel file containing all of the information extracted from that copy, discovered KakaoTalk conversations relating to the defendant's alleged leakage of military secrets for the purpose of obtaining employment and obtained an additional warrant for search, seizure and inspection; and, continuing to analyse the Excel file, again discovered electronic information relating to the defendant's separate alleged leakage of military secrets concerning promotion selection results and alleged obstruction of exercise of rights by abuse of authority, and again obtained a warrant for search, seizure and inspection, the KakaoTalk conversations and the derivative evidence collected on the basis of them are all illegally obtained evidence and inadmissible

The referenced provisions to be read together in this case are: [1] Article 12 (1) and (3) of the Constitution of the Republic of Korea, and Articles 154, 254, 258 and 359-2 of the Military Court Act / [2] Article 12 (1) and (3) of the Constitution of the Republic of Korea, Articles 254, 359 and 359-2 of the Military Court Act, and Articles 215, 307 and 308-2 of the Criminal Procedure Act / [3] Article 12 (1) and (3) of the Constitution of the Republic of Korea, Articles 154, 254, 258, 359 and 359-2 of the Military Court Act, and Articles 215, 307 and 308-2 of the Criminal Procedure Act. The first step is to separate, among the constituent elements or the requirements for the arising of rights laid down by the wording of these provisions, how far the domain of statutory interpretation extends and where the domain of individual fact-finding begins.

In relation to prior precedent, this judgment stands in the position of following existing precedent. Read alongside the referenced precedents ([1] Supreme Court Order 2009Mo1190 dated May 26, 2011 (Gong2011Ha, 1342) and Supreme Court en banc Order 2011Mo1839 dated July 16, 2015 (Gong2015Ha, 1274) / [2] Supreme Court en banc Judgment 2007Do3061 rendered November 15, 2007 (Gong2007Ha, 1974), Supreme Court Judgment 2012Do13611 rendered March 14, 2013 (Gong2013Sang, 703), and Supreme Court Judgment 2015Do12400 rendered September 21, 2017 (Gong2017Ha, 2033)), it can be seen how the Court, while maintaining the outer limits of existing legal principles, rearranged the factual elements of the specific case.

Sources for this section: Supreme Court Judgment 2020Do10908 rendered August 14, 2025 — Official text of the judgment, National Law Information Center

Analysis of the Gist of the Supreme Court Judgment and Its Key Holding

The core of the gist of the judgment stated by the Supreme Court is as follows. [1] A search and seizure of electronic information by an investigative agency must, in principle, be conducted by collecting as printed documents only the part related to the suspected offence that formed the grounds for issuing the warrant, or by copying the relevant files onto a storage medium carried by the investigative agency. A search and seizure conducted by directly taking the storage medium itself off-site, or by taking all the electronic files contained on the storage medium off-site, such as to the investigative agency's office, in the form of a hard copy, imaging or the like (hereinafter a "copy"), may be permitted only exceptionally, where it is recognised that printing or copying within a defined scope is impossible or would make it markedly difficult to achieve the purpose of the seizure, such as where, owing to the circumstances at the site or the large volume of electronic information, obtaining the relevant information would take a long time or technical measures by specialist personnel are required. Since the series of processes of examining the storage medium itself or a lawfully obtained copy and printing out as documents, or copying as files, the electronic information subject to seizure whose relevance to the suspected offence is recognised likewise forms, as a whole, part of a search and seizure based on a single warrant, it is self-evident, in light of the principles of due process and the warrant requirement under Article 12 (1) and (3) of the Constitution of the Republic of Korea and Articles 154 and 254 of the Military Court Act, or the principle of proportionality, that the objects of document printing or file copying in such a case must also be limited to the part related to the suspected offence, as in a search and seizure at the location of the storage medium. Accordingly, printing out as documents, or copying as files, electronic information arbitrarily stored on a storage medium or copy taken to the investigative agency's office or elsewhere, without distinguishing relevance to the suspected offence, constitutes, in principle, an unlawful seizure contrary to the warrant requirement principle. [2] Evidence collected without following due procedure shall not be admitted as evidence (Article 359-2 of the Military Court Act). In principle, not only evidence collected by an investigative agency without following the procedures prescribed by the Constitution of the Republic of Korea and the Military Court Act, but also derivative evidence obtained on the basis of such evidence, cannot be used as evidence to find guilt. However, in exceptional cases where the investigative agency's procedural violation does not infringe the substantive content of due process, and where, on the contrary, excluding the admissibility of the evidence is assessed as producing a result contrary to the purpose of the Constitution of the Republic of Korea, the Criminal Procedure Act and the Military Court Act in establishing procedural provisions on criminal proceedings, namely to harmonise the principle of due process with the ascertainment of the substantive truth and thereby to realise criminal justice, the court may use the evidence to find guilt. When finally determining the admissibility of derivative evidence, the court must first examine all circumstances relating to the collection of the primary evidence without following due procedure, namely the purpose of the procedural provision and the content and degree of its violation, the specific circumstances of the violation and its avoidability, the nature and degree of infringement of the rights or legal interests that the procedural provision seeks to protect and their connection with the defendant, the degree of connection such as the causal link between the procedural violation and the collection of evidence, and the awareness and intent of the investigative agency; and further, it must consider, as a whole and comprehensively, all circumstances additionally arising in the course of collecting derivative evidence on the basis of the primary evidence, focusing mainly, according to the specific case, on whether the causal link has been attenuated or severed. [3] A case holding that, where a Military Prosecutor of the Special Investigation Unit on the Defense Security Command allegations obtained a warrant for search, seizure and inspection concerning A's alleged conspiracy to commit insurrection, etc., seized the mobile phone of the defendant, who had been a witness in relation to the offence concerned, and created a copy of it; then, while analysing an Excel file containing all of the information extracted from that copy, discovered KakaoTalk conversations relating to the defendant's alleged leakage of military secrets for the purpose of obtaining employment and obtained an additional warrant for search, seizure and inspection; and, continuing to analyse the Excel file, again discovered electronic information relating to the defendant's separate alleged leakage of military secrets concerning promotion selection results and alleged obstruction of exercise of rights by abuse of authority, and again obtained a warrant for search, seizure and inspection: the series of procedures by which the Excel file was generated from the copy of the mobile phone and used to obtain the KakaoTalk conversations was an unlawful seizure contrary to the warrant requirement principle and the principle of due process; its illegality cannot be regarded as cured merely because the KakaoTalk conversations were subsequently seized under a later-issued warrant for search, seizure and inspection; the violation of the seizure procedure does not fall within a case in which an exception to the exclusionary rule for illegally obtained evidence may be recognised; and the evidence collected on the basis of the KakaoTalk conversations, being illegally obtained evidence, is likewise derivative evidence obtained on the basis of illegally obtained evidence, and since the causal link between the seizure procedure and the collection of the derivative evidence cannot be regarded as attenuated or severed, it is inadmissible; and that, on these grounds, the lower court's judgment, which held otherwise and recognised the admissibility of the KakaoTalk conversations and of the evidence collected after the execution of the additional warrant for search, seizure and inspection, was erroneous in that it misapprehended the legal principles on the exclusionary rule for illegally obtained evidence.

In particular, the passage of the judgment that directly supports the conclusion is the following: "Printing out as documents, or copying as files, electronic information arbitrarily stored on a storage medium or copy taken to the investigative agency's office or elsewhere, without distinguishing relevance to the suspected offence, constitutes, in principle, an unlawful seizure contrary to the warrant requirement principle."

This sentence does not stop at an abstract declaration; it operates as the benchmark for identifying which legal premise the lower court omitted, or which factual elements it overstated or understated.

Sources for this section: Supreme Court Judgment 2020Do10908 rendered August 14, 2025 — Official text of the judgment, National Law Information Center

Key Factors Identified by the Judgment and a Record Comparison Table

The table below sets out the factors to which the Court attached importance in Judgment 2020Do10908 and the role each factor played in the operative part (partial reversal and transfer).

Sources for this section: Supreme Court Judgment 2020Do10908 rendered August 14, 2025 — Official text of the judgment, National Law Information Center

Competing Readings of the Same Facts

In this case, one reading regards the generation of the Excel file as a preparatory procedure for selecting electronic information related to the suspected offence under the first warrant, and considers it difficult to conclude that information unrelated to the suspected offence was indiscriminately examined in the course of executing the warrant. By contrast, the Supreme Court's legal principles examine whether the object of the search and seizure was limited to the part related to the suspected offence and, as regards derivative evidence, consider all circumstances of the collection of the primary and derivative evidence as a whole and comprehensively, focusing on whether the causal link has been attenuated or severed.

Accordingly, when analysing similar cases, one should not merely cite the concluding sentence, but should test, as a counter-hypothesis, how the conclusion would change if any one of the factors listed in the table above were absent.

Sources for this section: Supreme Court Judgment 2020Do10908 rendered August 14, 2025 — Official text of the judgment, National Law Information Center

Remaining Questions and Conditions for Re-examination

A follow-up question remaining after reading this judgment is the following: if the investigative agency had limited the scope of extraction to a period close to the date and time of the offence, could bulk printing be permitted?

It is also clear when this analytical framework should be re-examined as subsequent materials or precedents accumulate: if Article 359-2 of the Military Court Act is amended, this reading should be revisited.

This is a research analysis prepared by comparing the original text of Supreme Court Judgment 2020Do10908 rendered August 14, 2025, as published on the National Law Information Center, and its referenced provisions as of October 21, 2026; it does not substitute for the conduct of litigation by, or legal advice to, any particular party.

Sources for this section: Supreme Court Judgment 2020Do10908 rendered August 14, 2025 — Official text of the judgment, National Law Information Center