Admissibility of Unlawfully Obtained Electronic Information and Evidence from Defective Seizure Procedures: A Review of Three Supreme Court Judgments

Question

How far does inadmissibility extend to derivative evidence (fruit of the poisonous tree) obtained on the basis of electronic information collected through unlawful procedures, and specifically to statements made by the defendant in court after undergoing an unlawful investigation by the investigative authorities? The first question of this brief is how the purposes of due process and the right to remain silent, guaranteed by Article 12(1) and (3) of the Constitution of the Republic of Korea, operate with respect to derivative evidence.

Second, where the person who controls or manages the items subject to search and seizure is a minor with mental capacity, to whom must the warrant be presented? The issue is whether presenting the warrant to the person with parental authority and giving that person an opportunity to participate is sufficient to satisfy the procedural requirements of Articles 118, 121 and 219 of the Criminal Procedure Act, or whether presentation and participation must each be guaranteed to the minor himself or herself and to his or her defence counsel.

Third, where the investigative authorities seize items at the scene of a crime without a warrant and then request an ex post search and seizure warrant that is rejected, how strictly should their duty of immediate return be enforced? The issues are the scope of special circumstances that make immediate return markedly difficult, and whether the defendant's consent to the use as evidence of seized items that were not immediately returned can cure the exclusionary effect.

Material to check

First of all, the full texts of the three judgments and the provisions cited in them must be checked. The wording of Article 12(1) and (3) of the Constitution of the Republic of Korea, Articles 307, 308, 308-2, 216(3) and 318(1) of the Criminal Procedure Act, and Articles 118, 121 and 219 of the former Criminal Procedure Act must first be compared with the standards set out in the judgments and with where the burden of proof under those standards lies.

Next, obtain the application for the search and seizure warrant, a copy of the warrant issued, and the records of its execution. The key materials for assessing procedural lawfulness are the execution report stating when and to whom the warrant was presented, the inventory prepared at the scene, whether the minor and the person with parental authority were present, and documents recording any request for the participation of defence counsel and how it was handled.

Materials showing how the electronic information was collected must not be overlooked either. By checking the forensic reports on the mobile phone and storage media, the date, time and scope of collection, the measures taken to preserve the originals, how the call recording files newly obtained under the second search and seizure warrant were acquired, and whether they overlap with the existing material, the boundary between unlawfully obtained evidence and independent evidence can be drawn.

Finally, check the materials relating to the interrogation of the suspect and to the trial. The circumstances in which the suspect interrogation records were prepared, the audio recordings and transcripts of the defendant's statements in court, records arranged by date that show how the experience of the unlawful investigation affected the formation of those statements, and the records of the custody and return of the seized items provide the basis for determining whether the duty of immediate return was performed.

Possible readings

The reading favourable to the prosecution treats exclusion as a rule with a deterrent purpose and narrows its scope of application. On this view, no exclusionary effect arises where the investigative authorities' violation did not reach the point of infringing the essence of the procedure, where the causal link between the collected evidence and the derivative evidence has been weakened by the passage of time or by an independent route of acquisition, or where consent to the use of the evidence has been given. It is also emphasised that items seized at the scene without a warrant may be treated separately from material later re-obtained on an independent basis.

The reading favourable to the defendant treats the exclusionary rule as a substantive guarantee under Article 12 of the Constitution of the Republic of Korea and applies it broadly. On this view, the prosecutor must prove, by concrete and special circumstances, that the attenuation or severance of the causal link falls within an exception, and unless this is proved, both the unlawfully obtained electronic information and the in-court statements based on it must be excluded from the evidence used to establish guilt. If the duty to present the warrant is seen not as a formal requirement but as a procedure guaranteeing the right of defence of the person subject to the disposition, it can be argued that items seized without presenting the warrant to the minor himself or herself must also be excluded.

The third axis of disagreement concerns whether the effect of a procedural violation is relative or absolute. One reading treats Article 216(3) and Article 308-2 of the Criminal Procedure Act, under which a breach of the duty of immediate return is a ground for exclusion, as mandatory provisions whose effect cannot be undone even by consent to the use of the evidence; the opposing reading holds that exceptions may be broadened in light of the defendant's voluntary consent to the use of the evidence or the principle of proportionality. On whether the duty to present a warrant to a minor should be construed broadly or narrowly, views are likewise divided between those that give priority to the protective purpose and those that stress the limits of the statutory wording.

What the decisions held

Supreme Court 2023Do12127 (rendered 20 November 2025) stated expressly that, as a rule, not only evidence collected without following the procedures prescribed by the Constitution of the Republic of Korea and the Criminal Procedure Act but also derivative evidence obtained on the basis of such evidence may not be used as evidence to establish guilt. The defendant's in-court statements based on unlawfully obtained electronic information also constitute derivative evidence and are excluded; an exception is recognised only in exceptional cases where, considered as a whole and comprehensively, the causal link is assessed as having been attenuated or severed. The prosecutor must prove that there are concrete and special circumstances warranting such an exception.

Supreme Court 2022Do2071 (rendered 24 December 2024), relying on Article 12(3) of the Constitution of the Republic of Korea and Articles 118, 121 and 219 of the former Criminal Procedure Act, held that where the person subject to the search and seizure disposition is a minor with mental capacity, the warrant must be presented to that minor, and presentation of the warrant to the person with parental authority cannot substitute for it. Whether an opportunity to participate was guaranteed must likewise be assessed by reference to the minor with mental capacity himself or herself or his or her defence counsel, and the mere fact that the person with parental authority was given an opportunity to participate cannot serve as a basis for curing or legitimising the procedural violation. In that case, the procedural violation leads to a determination of admissibility under Article 308-2 of the Criminal Procedure Act.

Supreme Court 2024Do10062 (rendered 8 October 2024) held that where items seized at the scene of a crime without a warrant under Article 216(3) of the Criminal Procedure Act become the subject of a request for an ex post search and seizure warrant and no warrant is issued, the investigative authorities must immediately return the seized items, and seized items not immediately returned may not be used as evidence of guilt. Immediate return means that, unless there are special circumstances making immediate return markedly difficult, the return procedure must be initiated at the very moment the warrant is rejected and the situation before the seizure must be restored without delay. Even if consent to the use of the evidence has been given under Article 318(1) of the Criminal Procedure Act, this exclusionary effect is not cured.

Practical checklist

First, check who is identified in the case record as the person to whom the search and seizure warrant was presented. If the person subject to the disposition is a minor, the basis for assessing that minor's mental capacity, the time and manner of the warrant's presentation, and whether the procedure was completed solely by presentation to the person with parental authority must be cross-checked against the execution report and the records made at the scene.

Second, set out the route by which the evidence at issue was obtained in chronological order and map the links between the unlawfully obtained evidence and the derivative evidence. Place side by side the time at which the electronic information was collected, the scope of the forensic examination, the time at which the in-court statements were formed, and how the files newly obtained under the second search and seizure warrant were acquired, and examine what grounds exist for arguing that the causal link was attenuated or severed.

Third, check whether the seized items were returned at the time required by law. Confirm from the records the interval between the rejection of the ex post search and seizure warrant and the initiation of the return procedure, the records of any change in the place of custody, and the extent to which the situation before the seizure was restored; and if there were special circumstances making immediate return markedly difficult, examine whether there is material supporting those circumstances.

Fourth, review how the burden of proof and consent to the use of evidence have been handled. On the premise of the standard that the prosecutor must prove the exceptional circumstances amounting to attenuation or severance of the causal link, distinguish the evidence presented by the prosecution from the points contested by the defence, and confirm from the records whether consent to the use of the evidence was given through a lawful procedure and how far the effect of that consent extends.

Glossary

The exclusionary rule for unlawfully obtained evidence is the rule that evidence collected in breach of the procedures prescribed by the Constitution of the Republic of Korea and the Criminal Procedure Act may not be used as evidence to establish guilt. Article 308-2 of the Criminal Procedure Act provides that evidence collected without following due process may not be admitted as evidence, and the rule rests on the purpose of reconciling the principle of due process with the discovery of the substantive truth and thereby realising justice in criminal adjudication.

Derivative evidence (fruit of the poisonous tree) means evidence subsequently obtained as a result of the original unlawfully obtained evidence. An example is the defendant's in-court statement arising from an inquiry conducted on the basis of the contents of unlawfully obtained electronic information. By contrast, evidence secured through an independent route unrelated to the unlawfully obtained evidence is not excluded in itself, and the key criterion for distinguishing the two is the causal link between the collected evidence and the subsequent evidence.

The duty of immediate return is the duty, under Article 216(3) of the Criminal Procedure Act, of the investigative authorities to return items seized without a warrant immediately where they have requested an ex post search and seizure warrant and failed to obtain it. Article 318(1) of the Criminal Procedure Act provides that documents or articles which the public prosecutor and the defendant have consented to admit as evidence may be admitted as evidence when they are found to be authentic; Supreme Court 2024Do10062 held that such consent does not cure the exclusionary effect arising from a breach of the duty of immediate return.

Sources and limitations

This brief is based only on the provisions of the Constitution of the Republic of Korea, the Criminal Procedure Act, the former Criminal Procedure Act, the Criminal Act and the Korea Environmental Industry and Technology Institute Act as checked on the National Law Information Center, and on the judgments in Supreme Court 2023Do12127, Supreme Court 2022Do2071 and Supreme Court 2024Do10062, and reflects the materials as of 15 October 2026. The judgments cited are limited to these three, and no other case numbers or precedents are included.

This material is a summary of judicial issues prepared for general research purposes; it is not legal advice on any particular matter and does not replace the advice of an attorney. No decision on litigation or on responding to an investigation should be made on the basis of this brief alone without directly checking the full text of the judgments and whether the relevant legislation has recently been amended; in any specific matter, the original judgments and the relevant records must be checked and the matter must be reviewed by the attorney handling it.

Points left open

The first remaining issue is whether the additional call recording files newly collected under the second search and seizure warrant can be recognised as independent evidence despite their connection with the unlawfully obtained electronic information. Supreme Court 2023Do12127 stated that attenuation or severance of the causal link may be recognised if the defendant's in-court statements are assessed as having been made independently of the primary evidence, for example because they derived from other independent evidence, but that the prosecutor must prove that such special circumstances exist; accordingly, whether such an exception is in fact recognised for those additional call recording files is not settled by the standard in Supreme Court 2023Do12127 alone.

The second remaining issue is to whom the warrant must be presented when seizing items controlled or managed by a minor without mental capacity, and what counts as special circumstances making it markedly difficult for the investigative authorities to return seized items immediately. Since the three judgments did not directly set out the standards for deciding such borderline cases or specific categories of cases, these matters need to be settled in future case law.

When to reconsider

This brief must be reviewed in its entirety if Articles 308-2, 216(3), 318(1), 118, 121 or 219 of the Criminal Procedure Act are amended or the wording of the relevant provisions changes, or if the Supreme Court renders a judgment supplementing or altering the standards of the three judgments covered by this brief.

In addition, if a new interpretation by the Supreme Court or a trend in lower-court judgments emerges concerning the scope of exclusion of unlawfully obtained electronic information, the duty to present a warrant to a minor, or the time by which the duty of immediate return must be performed, or if material is obtained in which the degree of a procedural violation or the effect of consent to the use of evidence was assessed differently in a given case, the relevant parts must be updated and the description of the standards and the burden of proof must be revised.

Statutes referred to

• 헌법 제12조 제1항, 제12조 제3항
• 형사소송법 제118조, 제121조, 제216조 제3항, 제219조, 제307조, 제308조, 제308조의2, 제318조 제1항
• 구 형사소송법(2022. 2. 3. 법률 제18799호로 개정되기 전의 것) 제118조, 제121조, 제219조
• 형법 제129조 제1항, 제133조 제1항
• 한국환경산업기술원법 제32조

Decisions referred to

• 대법원 2025. 11. 20. 선고 2023도12127 판결 · Decision ledger
• 대법원 2024. 12. 24. 선고 2022도2071 판결 · Decision ledger
• 대법원 2024. 10. 8. 선고 2024도10062 판결 · Decision ledger

Verification status

The texts of the relevant provisions and the judgments in Supreme Court 2023Do12127, Supreme Court 2022Do2071 and Supreme Court 2024Do10062 were checked against the National Law Information Center as of 15 October 2026. This brief cites only the three judgments listed among the decisions covered.