Where flight and communications logs of an operational unmanned system are remotely copied and printed without regard to relevance, does this violate the warrant requirement, and what becomes of the admissibility of the evidence?

The Anchor in Actual Precedent and the Question Posed by the Future Synthetic Case

Supreme Court Decision 2020Do10908 rendered on August 14, 2025 (Leakage of Military Secrets, Abuse of Authority and Obstruction of the Exercise of Rights, and Disclosure of Official Secrets [a case in which a separate offence was discovered, and charged, in the course of exploring 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 an 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 or copying from a removed copy without distinguishing relevance is, in principle, an unlawful seizure contrary to the warrant requirement. It further held that derivative evidence (fruit of the poisonous tree) obtained on the basis of illegally collected evidence likewise may not, in principle, be used as evidence for a finding of guilt. Such evidence may be used only in exceptional cases, such as where the procedural violation does not infringe the substantive content of due process. Whether such an exception applies is to be determined by considering all the circumstances of the evidence gathering as a whole and comprehensively, with a focus on whether the causal link has been 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 reasoning is a statement of requirements (following existing precedent).

Taking the doctrine of the above actual judgment as its anchor, this research pair applies it to a hypothetical case set in 2032. In that case, for the purpose of investigating a security incident at a military air wing, unmanned aerial vehicle operation logs synchronised to a control server and the personal communications cache of a pilot officer were remotely imaged without notice to the persons concerned. The pair compares, step by step, which requirements operate unchanged in that setting and at which requirements new gaps in proof arise.

Sources for this section: Supreme Court Decision 2020Do10908 rendered on August 14, 2025 — official text of the decision, National Law Information Center

The Structure of the Issues Set by the Points of Decision and the Referenced Provisions

The framework of the points of decision, 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 remove the storage medium itself or a copy of it to a location outside, such as the investigative agency's office / Whether printing out as documents or copying as files electronic information arbitrarily stored on a storage medium or copy removed to the investigative agency's office or elsewhere, without distinguishing relevance to the suspected offence, constitutes an unlawful seizure contrary to the principle of the warrant requirement (affirmative, in principle) [2] Whether evidence collected by an investigative agency without following the procedures prescribed by the Constitution and the Military Court Act, and derivative evidence obtained on the basis of it, may be used as evidence for a finding of guilt (negative, in principle), and the exceptional cases in which a court may use such evidence as evidence for a finding of guilt / The matters a court must consider when making its final determination on the admissibility of derivative evidence [3] A case holding that the KakaoTalk conversations, and the derivative evidence collected on the basis of them, were all illegally obtained evidence and inadmissible. In that case, a military prosecutor of the special investigation team on the Defense Security Command allegations obtained a warrant of seizure, search and inspection concerning A's alleged conspiracy to commit insurrection and other offences. The prosecutor seized the mobile phone of the defendant, who had been a witness in relation to those criminal facts, and created a copy. While analysing an Excel file of all the information extracted from that copy, the prosecutor discovered KakaoTalk conversations relating to the defendant's alleged leakage of military secrets for the purpose of obtaining employment, and obtained an additional warrant of seizure, search and inspection. Continuing to analyse the Excel file, the prosecutor again discovered electronic information relating to the defendant's separate alleged leakage of military secrets concerning promotion selection results and alleged abuse of authority and obstruction of the exercise of rights, and once more obtained a warrant of seizure, search and inspection.

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; 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; 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; 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 set by the wording of these provisions, the part that belongs to statutory interpretation from the part that belongs to fact-finding in the individual case.

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

Sources for this section: Supreme Court Decision 2020Do10908 rendered on August 14, 2025 — official text of the decision, National Law Information Center

Analysis of the Supreme Court's Summary of Judgment and Its Key Holdings

The core of the summary of judgment set out by the Supreme Court is as follows. [1] A search and seizure of electronic information by an investigative agency must, in principle, be carried out either by collecting as printed documents only the part relating to the suspected criminal facts on which the issuance of the warrant was based, or by copying the relevant files onto a storage medium carried by the investigative agency. Conducting a search and seizure by directly removing the storage medium itself, or by removing all the electronic files on that storage medium in the form of a hard copy, imaging or the like (hereinafter a "copy") to a location outside, such as the investigative agency's office, 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, as where obtaining the relevant information would take a long time because of the circumstances at the site or the large volume of electronic information, or where technical measures by specialist personnel are required. The series of steps by which the storage medium itself, or a lawfully obtained copy, is explored and the electronic information subject to seizure whose relevance to the suspected offence is recognised is printed out as documents or copied as files likewise forms, as a whole, part of a search and seizure based on a single warrant. It is therefore self-evident, in light of the principles of due process and the warrant requirement and the principle of proportionality under Article 12 (1) and (3) of the Constitution of the Republic of Korea and Articles 154 and 254 of the Military Court Act, that the objects of document printing or file copying in such a case must, as with a search and seizure at the location of the storage medium, be limited to the part relating to the suspected offence. Accordingly, printing out as documents or copying as files electronic information arbitrarily stored on a storage medium or copy removed to the investigative agency's office or elsewhere, without distinguishing relevance to the suspected offence, is in principle an unlawful seizure contrary to the principle of the warrant requirement. [2] Evidence collected without following due process may not be admitted as evidence (Article 359-2 of the Military Court Act). Not only evidence collected by an investigative agency without following the procedures prescribed by the Constitution and the Military Court Act, but also derivative evidence obtained on the basis of it, may not, in principle, be used as evidence for a finding of guilt. However, a court may use such evidence as evidence for a finding of guilt in exceptional cases where the investigative agency's procedural violation does not infringe the substantive content of due process, and where excluding the evidence would instead be assessed as producing a result contrary to the purpose for which the Constitution, the Criminal Procedure Act and the Military Court Act established 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. When a court makes its final determination on the admissibility of derivative evidence, it must first examine all the circumstances relating to the collection of the primary evidence without following due process, namely the purpose of the procedural provision and the content and degree of its violation, the specific circumstances of the violation and whether it could have been avoided, the nature of the rights or legal interests the procedural provision seeks to protect, the degree of their infringement and their relationship to the defendant, the degree of connection such as the causal link between the procedural violation and the collection of the evidence, and the awareness and intent of the investigative agency. It must further consider, as a whole and comprehensively according to the specific case, all the circumstances additionally arising in the course of collecting the derivative evidence on the basis of the primary evidence, focusing mainly on whether the causal link has been attenuated or severed. [3] The facts were as follows. A military prosecutor of the special investigation team on the Defense Security Command allegations obtained a warrant of seizure, search and inspection concerning A's alleged conspiracy to commit insurrection and other offences. The prosecutor seized the mobile phone of the defendant, who had been a witness in relation to those criminal facts, and created a copy. While analysing an Excel file of all the information extracted from that copy, the prosecutor discovered KakaoTalk conversations relating to the defendant's alleged leakage of military secrets for the purpose of obtaining employment, and obtained an additional warrant of seizure, search and inspection. Continuing to analyse the Excel file, the prosecutor again discovered electronic information relating to the defendant's separate alleged leakage of military secrets concerning promotion selection results and alleged abuse of authority and obstruction of the exercise of rights, and once more obtained a warrant of seizure, search and inspection. The Supreme Court held as follows. The series of procedures by which an 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 and the principle of due process. The illegality cannot be regarded as cured merely because the KakaoTalk conversations were subsequently seized under a later-issued warrant of seizure, search and inspection. The violation in the seizure procedure does not fall within a case in which an exception to the exclusionary rule for illegally obtained evidence may be recognised. The evidence collected on the basis of the KakaoTalk conversations, themselves illegally obtained evidence, is likewise derivative evidence obtained on the basis of illegally obtained evidence, and it cannot be said that the causal link between the seizure procedure and the collection of the derivative evidence was attenuated or severed, so that its admissibility cannot be recognised. On these grounds, the Court held that the lower court, which had reached the contrary conclusion and recognised the admissibility of the KakaoTalk conversations and of the evidence collected after execution of the additional warrant of seizure, search and inspection, erred by misapprehending the legal principles on the exclusionary rule for illegally obtained evidence.

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

This sentence is more than an abstract declaration. It serves as the standard for identifying which doctrinal premise the lower court omitted, or which factual elements it overstated or understated.

Sources for this section: Supreme Court Decision 2020Do10908 rendered on August 14, 2025 — official text of the decision, National Law Information Center

Comparison Table: Elements of Decision in the Actual Judgment and the Synthetic Case

The table below sets out the elements of decision drawn from Decision 2020Do10908 and compares them side by side with the record structure of the synthetic case.

Sources for this section: Supreme Court Decision 2020Do10908 rendered on August 14, 2025 — official text of the decision, National Law Information Center

Two Competing Doctrinal Readings of the Synthetic Case

In the synthetic case (a hypothetical case set in 2032, in which, for the purpose of investigating a security incident at a military air wing, unmanned aerial vehicle operation logs synchronised to a control server and the personal communications cache of a pilot officer were remotely imaged without notice to the persons concerned), the first reading emphasises the outward result and the economic and functional effects, and argues for extending the doctrine of the existing precedent (2020Do10908) as it stands. On this view, even if the technical means or the contractual form have changed, the risk the norm seeks to prevent and the legal interest it seeks to protect remain the same.

The second reading counters, citing the strict limits of the principle of legality in criminal law (nullum crimen sine lege) and of private autonomy and the principle that rights are created only by law, that the factors Decision 2020Do10908 considered in determining the admissibility of derivative evidence, such as the awareness and intent of the investigative agency and whether the causal link has been attenuated or severed, cannot be applied by analogy to algorithms or distributed ledger structures. Its reasoning is that, within the wording of the current provisions, it is difficult to attribute responsibility without legislative supplementation.

Sources for this section: Supreme Court Decision 2020Do10908 rendered on August 14, 2025 — official text of the decision, National Law Information Center

Remaining Questions and Conditions for Re-examination

A follow-up question that remains 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 further materials or precedents accumulate. If Article 359-2 of the Military Court Act is amended, this reading must be revisited.

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

Sources for this section: Supreme Court Decision 2020Do10908 rendered on August 14, 2025 — official text of the decision, National Law Information Center