Hello. I am attorney Lee Kyung-Jun of Cheongchul Law Firm.

In Korean criminal trials, the single phrase "DNA was detected" is treated as one of the most powerful pieces of evidence. In sex crime cases especially, the defendant's DNA found on the victim's clothing or bedding often functions as the decisive evidence dividing guilt from innocence.

But should the mere fact that "DNA was detected" lead directly to a conviction? The Supreme Court of Korea recently handed down a ruling that re-clarified the clear limits on this point.

The Supreme Court Decision 2026Do4423 dated May 29, 2026 (rape, reversed and remanded) consolidated (i) the limits on an appellate court overturning a first-instance acquittal and (ii) the standards for admitting the probative value of scientific evidence including DNA, carrying significant weight in criminal defense practice.

1. Overview of the case

The defendant was indicted for raping the victim on August 27, 2021. The trial court rendered an acquittal, citing doubts about the credibility of the victim's statement.

However, at the appellate court, the prosecution submitted as new evidence "the pants the victim claimed to have been wearing at the time," produced on January 26, 2024 — approximately two years and five months after the date of the incident. The pants contained not only the defendant's DNA but also the victim's DNA and DNA of an unidentified male. Based on this, the appellate court overturned the acquittal and convicted the defendant.

The Supreme Court found that the appellate court had misapplied (i) the doctrine on the post-review and continuing-trial structure of the appellate process and (ii) the standards for admitting the probative value of scientific evidence, and accordingly reversed and remanded the case.

2. When an appellate court may overturn a first-instance acquittal

Under the Korean Criminal Procedure Act, the appellate court is built on a "continuing-trial" structure that inherits the first-instance record and re-evaluates the facts, while also incorporating a "post-review" function that assesses the propriety of the first-instance ruling. This is referred to as a "post-reviewing continuing trial" in scholarly terms.

The Supreme Court held that to overturn a first-instance ruling, the appellate court must satisfy one of two conditions: (i) the first instance's evaluation of the evidence is clearly mistaken such that maintaining it would be markedly unjust, or (ii) new objective material capable of influencing the formation of conviction emerges during the appellate hearing.

It is not enough for the appellate panel to merely "disagree with the first instance." Either maintaining the first-instance ruling must be markedly unjust, or new objective material must be added at the appellate stage.

3. Standards for admitting the probative value of scientific evidence (such as DNA)

The Supreme Court held that for scientific evidence supporting the charges to carry "substantial binding force" in fact-finding, (i) all of its underlying facts must be proven true and (ii) the method of inference must be scientifically sound, with no possibility of error or only a negligible one.

Specifically, the Court required that (i) the evidentiary method be analyzed by an expert with professional knowledge, skill, and experience using a publicly recognized standard testing technique, and (ii) the chain of collection, custody, and analysis be such that the identity of the material is preserved and that no artificial manipulation, damage, or addition has occurred.

It particularly noted that the more scientific evidence stands as the sole or dominant proof of the charges, the greater the risk that "blind trust in scientific authority" will erode the principle of strict proof. The more powerful evidence appears in a single line — like DNA analysis — the more rigorously courts must examine "how the evidence was actually produced."

4. Why the Supreme Court reversed the appellate ruling in this case

First, the pants — the object of the DNA report newly admitted by the appellate court — were produced only after two years and four months had passed since the date of the incident, and the custody process and the reasons for the delayed submission had not been examined.

Second, in addition to the defendant's and the victim's DNA, the pants contained DNA of an unidentified male, suggesting that the pants may have been exposed to external factors after the incident or that other circumstances may have intervened.

In light of these circumstances, the Supreme Court held that the prosecution needed to provide additional proof regarding the custody, identity preservation, and absence of manipulation, and that the appellate court should have re-examined the credibility of the victim's statement on that basis, or separately considered whether credibility could be acknowledged based on the remaining evidence excluding the DNA report — and accordingly reversed and remanded the case.

5. Practical significance of this ruling

This ruling has once again clarified the standard of control over the process by which an acquittal at first instance is reversed on appeal. The mere fact that the prosecution submits new evidence on appeal does not justify overturning a first-instance acquittal; the evidence must rise to a level that makes maintaining the first-instance ruling "markedly unjust."

The ruling also clarifies that "belatedly submitted evidence" produced long after the incident may have inherent limits on its probative force. From the defense perspective, it becomes necessary to actively contest the custodial party, custodial environment, and reasons for delayed submission, and to verify the identity of the material throughout the collection, custody, and analysis processes.

The ruling applies as a general legal doctrine not only to sex crimes but also to other criminal cases such as assault, injury, and property crimes. It can be applied with the same standard to a variety of scientific evidence including CCTV, digital forensics, and drug analysis reports.

6. What clients should check at the early stage of a case

In cases where scientific evidence such as DNA, CCTV, or digital forensics is a core issue, the first thing to confirm is "when, where, by whom, and through what procedure the evidence was collected, preserved, and analyzed." Focusing only on "what the result was" is not enough.

Specifically, one must organize (i) whether the evidence was secured immediately after the incident or submitted with delay, (ii) what the custodial party and environment were from the time of the incident to the time of submission, (iii) whether the expert held public qualifications and used standard testing techniques, (iv) whether other traces such as third-party DNA or fingerprints were detected on the object, and (v) whether photographs, logs, and documents are in place to prove the identity of collection, custody, and analysis.

At the appellate stage, the defense must contest whether the prosecution's newly submitted evidence even qualifies as "new objective material that makes maintaining the first-instance ruling markedly unjust" within the meaning of the Supreme Court ruling above.

7. Conclusion

This Supreme Court ruling cautions against the risk that a criminal trial could be reduced to the single line "DNA was detected." It should be understood as a ruling that does not deny the weight of scientific evidence, but rather confirms the principle that its scientific quality must be "properly verified" before being accepted.

If your case is one in which scientific evidence such as DNA, CCTV, or digital forensics is the decisive issue — especially a case where a first-instance acquittal faces a crisis on appeal, or a case in which new evidence has emerged long after the incident — a precise re-examination is needed against the standards of this ruling. We recommend that you consult with a criminal defense attorney specializing in criminal cases as early as possible to design your defense strategy together.