The Presumption of Innocence — The Threshold the Prosecutor Must Cross

Mr. Park on the News

A short news item flashes by on the evening report: "Cash Envelope Disappears from Neighborhood Clothing Store... Police Investigate Man in His 30s." The screen shows the blurred back of a man pulling down his cap as he walks into a police station.

Hearing news like this, most people first think, "That person must have taken it." If the police are investigating, you figure there must be something to it.

A trial starts from the opposite side. This article covers what that starting point is and how it drives the trial. It is about who has to prove guilt, how much they must prove, and what a "not guilty" verdict says and does not say.

This article is a general explanation written about criminal trials in Korean courts. The explanation uses a single case all the way through: a cash envelope placed in the register drawer by a clothing store owner disappears, and Mr. Park, a customer who bought a shirt that afternoon, is investigated. Mr. Park and this incident are fictionalized to help understanding.

From Suspect to Defendant — Starting from Innocence

The police found Mr. Park in the store's card payment records. Mr. Park says he did go to the store that day, but knows nothing about the envelope. At this point, there is a name used to call Mr. Park. A suspect is a person whom investigative agencies suspect of having committed a crime and are investigating.

When the case is handed over to a prosecutor, the prosecutor decides whether to send it to trial. Indictment is the act in which a prosecutor requests a court to try a person's guilt. When the prosecutor indicts Mr. Park, the title in the news changes. A defendant is a person who has been indicted and is undergoing a criminal trial. Headlines like "Defendant in Clothing Store Theft Allegation Attends First Trial" appear at this stage.

Even though the title changes, the place where the law treats Mr. Park remains the same. The Constitution states, "A criminal defendant shall be presumed innocent until a judgment of guilt has been finalized" (Article 27, Paragraph 4 of the Constitution). The Criminal Procedure Act repeats the same sentence (Article 275-2 of the Criminal Procedure Act). The presumption of innocence is the principle that a defendant must be treated as an innocent person until a judgment of guilt is finalized.

Weight rests on the word "finalized." That a judgment is finalized means that the avenues for further dispute have ended and that the judgment is set in stone. Even if guilt is found in the first trial, the presumption continues as long as avenues to dispute it remain. The paths to dispute a judgment are covered in "Korea's Three-Tier Courts and the Supreme Court — The Three Steps a Case Climbs, and Sometimes Comes Back Down".

Although the sentence in the Constitution wrote "criminal defendant," the Constitutional Court has maintained the position that even a suspect who has not yet been indicted must, in principle, be treated similarly to a person without guilt until there is a finalized judgment of guilt, and that even if disadvantages are imposed, they must be kept to the necessary minimum (KCI ART001687819).

Then why are people who are presumed innocent sometimes locked up? Locking people up before a trial ends is called detention. Explanations for this question are divided. The fork in the road is whether the presumption of innocence is a principle that governs even detention.

One side thinks it is. According to the summary of one paper, the view widely accepted in the Korean academic community counts limiting detention as one of the elements of the presumption of innocence, and acknowledges detention only in exceptional circumstances where it is difficult to achieve the purpose of criminal procedure by other methods. In a way, the presumption of innocence blocks detention while also placing exceptions within it.

The other side thinks not. The author who wrote that paper is on this side, so they disagree with the former view. The presumption of innocence is inherently a standard telling one to judge in favor of the defendant when it is unclear whether they are guilty or innocent, so it is difficult to extend it to the principle governing detention (DOI: 10.38133/cnulawreview.2019.39.3.169).

Another paper stands on the same side. What the presumption of innocence prohibits is disadvantages imposed on the premise of guilt, but detention is not such a punishment. It is viewed as a disadvantage temporarily inflicted when there are substantial grounds to suspect a crime has been committed and reasons such as the risk of flight or destruction of evidence are added, so the principle of the presumption of innocence does not prohibit it. That does not mean detention should be made easy. This paper finds the basis for reducing detention not in the presumption of innocence, but in other constitutional principles such as the right to liberty (DOI: 10.17007/klaj.2025.74.1.006). To summarize, on one side, detention is an exception to the presumption of innocence, and on the other side, detention is a matter that the presumption of innocence does not deal with.

The word "presumption" sounds like a guess. One paper explains that the presumption of innocence is not a principle that weighs whether Mr. Park actually took the envelope or not. Therefore, even if the probability of guilt seems to increase as the investigation proceeds, the presumption does not weaken by that much, and the procedure should be applied identically regardless of whether the charge is strong or weak (DOI: 10.21795/kcla.2024.36.3.233). However, the same paper notes separately that measures restricting fundamental rights, such as locking a person up, require a degree of suspicion commensurate with them. The strength of the suspicion does not make the presumption of innocence weaker, but it affects what coercive measures can be used.

A trial starts from the position where the defendant is innocent, and even if suspicions look dark, that starting point does not shift. Mr. Park faces trial standing on this side of the threshold, in the place of innocence.

The Burden of Proof Is the Prosecutor's

In the courtroom, does Mr. Park have to prove "I did not take the envelope"? He does not need to.

The burden of proof is the question of who bears the unfavorable consequence when a fact is not proven. In a criminal trial, the responsibility to prove the facts of the crime lies with the prosecutor (DOI: 10.22397/wlri.2020.36.2.21). If the prosecutor fails to prove that Mr. Park took the envelope, the unfavorable consequence falls on the prosecution side. Mr. Park is not found guilty.

This is precisely what the presumption of innocence does inside a trial. One paper summarizes that the presumption of innocence works as a rule determining who bears the burden of proof and how much must be proven, and also works as a rule preventing disadvantages based on the premise of guilt (DOI: 10.17007/klaj.2025.74.1.006). Only when the prosecutor brings evidence and crosses the threshold does Mr. Park move toward being guilty.

The first requirement of the Criminal Procedure Act is short: "The recognition of facts must be based on evidence" (Article 307, Paragraph 1 of the Criminal Procedure Act). Both the fact that the envelope disappeared and the fact that Mr. Park took it must be recognized through evidence.

The Constitution provides that no person shall be compelled to make a statement disadvantageous to themselves in a criminal case (Article 12, Paragraph 2 of the Constitution). This means Mr. Park cannot be forcibly pressured to speak words that are unfavorable to himself.

Some point out that the principle is not always cleanly upheld. According to one paper, when a defendant claims "I was somewhere else at that time," Supreme Court precedent makes it clear that the burden of proof for that also lies with the prosecutor. However, in criminal trial practice, there are not a few instances where the defendant appears to bear the burden of proof (DOI: 10.22397/wlri.2020.36.2.21).

The share of proving guilt belongs to the prosecutor, and the defendant does not have to prove their own innocence.

The Height of the Threshold — Reasonable Doubt

The prosecutor presents three things in the courtroom: a credit card receipt showing that Mr. Park bought a shirt that afternoon, a store video capturing the back of a hat-wearing man walking toward the register, and the owner's statement that "that customer stood near the register for a long time."

Is this enough? Hearing it, you get the feeling that "it seems likely." The threshold of a criminal trial is higher than that. The Criminal Procedure Act stipulates that "the recognition of criminal facts must reach a degree of proof that leaves no reasonable doubt" (Article 307, Paragraph 2 of the Criminal Procedure Act).

Reasonable doubt refers to a doubt that can be entertained in light of common sense, and for someone to be found guilty in a criminal trial, proof must be established to the extent that no such doubt remains. Applied to Mr. Park's case, it works like this. If questions like "Is the back in the video really Mr. Park?" and "Were there no other people in the store at that time?" remain in a common-sense way, the threshold has not been crossed.

This does not mean that every single doubt must be eliminated. Proof beyond a reasonable doubt does not require excluding every conceivable, unreasonable doubt, nor is it permissible to reject credible evidence based on doubts without a reasonable basis; this is the gist of a Supreme Court ruling introduced in a paper (DOI: 10.23102/kaccs.2019.27..015). A doubt such as "Maybe the envelope disappeared by itself" cannot stop the prosecutor from crossing the threshold.

Regarding why the threshold is set so high, a paper explains it this way: society considers it more wrong for an innocent person to be convicted than for a guilty person to go free, and requiring proof beyond a reasonable doubt can reduce the error of making an innocent person guilty (DOI: 10.16960/jhlr.13.2.201206.433).

The height of the threshold is not written in numbers. There is a view that it could be quantified in a way such that exceeding a certain percentage probability of guilt is enough, but there is a paper evaluating that one such method is very difficult to quantify and thus hard to adopt in criminal proceedings (KCI ART001977922). The earlier paper explaining why the threshold is set high also notes that while proof in criminal cases requires a high degree, presenting specific, objectified criteria remains difficult. This paper also records that, compared with Anglo-American jurisdictions, it is difficult to see the presumption of innocence as being properly guaranteed in Korean criminal trials (DOI: 10.16960/jhlr.13.2.201206.433).

"It seems likely" cannot cross the threshold, and a guilty verdict requires that no doubt worth entertaining in light of common sense remains.

Who Measures the Threshold?

Who measures whether the threshold has been crossed? The Criminal Procedure Act stipulates that "the probative value of evidence shall be determined by the free judgment of the judge" (Article 308 of the Criminal Procedure Act). Probative value refers to how compellingly evidence makes a fact believable. The principle of free evaluation of evidence is the rule that lets judges determine that probative value without a set formula. There is no calculation table that gives one video a certain score and a piece of testimony another.

Because a person is doing the measuring, different courts can reach different conclusions when looking at the same record. There is a study that analyzed 28 cases where lower courts and the Supreme Court disagreed, with "whether it exceeded reasonable doubt" as the issue. The factors that divided their conclusions were things prone to subjective judicial judgment, such as whether the statements of the defendant and the victim could be trusted, the probative value of circumstantial and other evidence, and the interpretation of scientific evidence (KCI ART001964380).

Civil trials have a provision by the same name. The Civil Procedure Act also states that a court, examining what is revealed in the trial and the evidence, determines through free judgment whether a factual assertion is true or not (Article 202 of the Civil Procedure Act). Yet this provision lacks the phrase "to the extent that there is no reasonable doubt." The Criminal Procedure Act separately sets down that threshold for the recognition of a criminal fact. How the two trials differ is covered in "How Is a Civil Case Different from a Criminal One? — One Incident, Two Courtrooms".

Whether the threshold has been crossed is determined not by a calculation table, but by a judge looking at the evidence.

Evidence Filtered Out at the Threshold — Confession

A confession sounds like strong evidence. The Criminal Procedure Act places two separate filters specifically on a defendant's confession. Using an investigative record in court as evidence has a separate set of additional conditions, which are not covered in this article.

The first filter is the process by which the confession was obtained. The Criminal Procedure Act stipulates that if there is reason to suspect that a defendant's confession was not made voluntarily through torture, violence, intimidation, unjustifiable prolonged confinement, deception, or other methods, it cannot be used as evidence of guilt (Article 309 of the Criminal Procedure Act). What the statute requires is not proof of coercion, but "reason to suspect."

The second filter is whether the confession stands alone. Even a voluntary confession cannot be used as evidence of guilt if it is the sole evidence disadvantageous to the defendant (Article 310 of the Criminal Procedure Act). If there is no evidence other than the confession, the confession alone cannot cross the threshold.

The Constitution also writes out these two same filters with the same intent (Paragraph 7 of Article 12 of the Constitution). The Constitution writes the first filter as "when recognized as not having been stated voluntarily," while the Criminal Procedure Act filters it out more broadly if there is "reason to suspect."

A confession suspected of not being made voluntarily cannot be used as evidence of guilt, and even a voluntary confession cannot serve as the basis for guilt if it is the only one. Because Mr. Park stated from beginning to end that he knew nothing about the envelope, this filter is irrelevant to Mr. Park's trial.

When in Doubt — Mr. Park’s Judgment

As the trial proceeds, several facts come to light. Two other customers were in the store during the time the envelope disappeared. The back of the person in the footage does not show a face, so it cannot be confirmed whether it is Mr. Park. No envelope was found at Mr. Park's home or in his car.

There is an old saying used in times like this. "When in doubt, in the defendant's interest" is the principle that when it is unclear whether someone is guilty or not guilty, the case must be decided in a way that favors the defendant. The widely accepted academic view we saw earlier counts this principle as one of the components of the presumption of innocence (DOI: 10.38133/cnulawreview.2019.39.3.169). Some explanations also cite both this principle and the presumption of innocence together as the reason why the prosecutor bears the burden of proof for criminal facts (DOI: 10.22397/wlri.2020.36.2.21).

The Criminal Procedure Act records its conclusion like this. When a defendant's case does not constitute a crime or when proof of the criminal facts is lacking, a verdict of not guilty must be pronounced (Criminal Procedure Act, Article 325). In this story, we can say that the court saw the evidence submitted by the prosecutor as leaving a reasonable doubt that Mr. Park took the envelope, and pronounced Mr. Park not guilty.

Not guilty means that the court does not recognize the person as having committed the crime. Mr. Park's not-guilty verdict is different from the sentence "It has been proven that Mr. Park is innocent." Proof of innocence is not necessary to pronounce a verdict of not guilty. This is because the law did not demand from the beginning that Mr. Park prove his innocence. At the same time, this judgment is also different from the sentence "Mr. Park took it but got away with it." The law placed Mr. Park in the position of being not guilty from the start, and the prosecutor failed to move Mr. Park from that spot.

What Mr. Park's not-guilty verdict says is that the prosecutor's proof failed to cross the threshold, which is different from meaning that his innocence was proven.

Reading the News Headline Again

A few days later, a headline like this appears: "30-something accused of clothing store theft found not guilty in the first trial... 'Insufficient evidence'." Taking what we saw earlier, let's read this headline.

"Not guilty" means the court did not recognize that Park took the bag. "Insufficient evidence" means not a case where it does not constitute a crime, but a case where the facts of the crime have not been proven, which means the prosecutor failed to cross the threshold. "First trial" means it is the initial trial, so if the prosecutor has paths left to contest it, the verdict is not yet final. Until it becomes final, Park is still presumed innocent. Even if guilty had come out in the first trial, that point would be the same.

Looking at the same headline, you might want to say, "They were just let go because there was no evidence." What the judgment contains goes only as far as saying there was no proof, and the "in fact, they did it" vibe that the word "just" gives off is nowhere in the judgment.

Opinions are divided on whether the presumption of innocence extends outside the courtroom, for example, to the news. The Constitutional Court views that the principle of the presumption of innocence applies not only to criminal procedures but also when restricting fundamental rights in other spheres of life outside of trials (KCI ART001687819). A paper dealing with crime reporting points out that, following this stance, there is room to see it as applying to crime reporting as well, but then does not view it that way. While not viewing the principle of the presumption of innocence as directly applicable to press reports, this paper notes that the press should respect that constitutional value and refrain from treating suspects and defendants as criminals before their guilt is finalized (KCI ART002624618).

"First trial not guilty, insufficient evidence" is news that the prosecutor's proof failed to cross the threshold, and until the judgment is finalized, that person is presumed innocent.

Where to Look Next

Whether the height of the threshold can be written down in numbers, or whether it should be, is a question that has not yet been answered.

How terms of address for people and types of trials are divided is covered in "How Is a Civil Case Different from a Criminal One? — One Incident, Two Courtrooms"; the paths for challenging a first-instance judgment and the process by which a judgment becomes final are covered in "Korea's Three-Tier Courts and the Supreme Court — The Three Steps a Case Climbs, and Sometimes Comes Back Down"; and how to read the top single line of a judgment and the reasons beneath it is covered in "How to Read a Court Judgment — A One-Line Answer and Its Reasons".

How scientific evidence brought into court to cross the threshold is verified is examined by the "The Court's Yardstick" series. The conditions set by the Supreme Court for using polygraph results as evidence are covered in ""If One Lies, Then Necessarily" — The Three Conditions Korea's Supreme Court Set for the Polygraph", and how figures calculated backward in drunk driving trials were accepted is covered in "The 0.003% That Decided It — How Korea's Supreme Court Let the Widmark Formula In".

Source Papers

• Constitution of the Republic of Korea, Article 12 — Current (enforced 1988.2.25) — Paragraph 2: Prohibition of coerced statements; Paragraph 7: Confessions lacking voluntariness and sole confessions cannot be used as evidence of guilt.
• Constitution of the Republic of Korea, Article 27 — Current (enforced 1988.2.25) — Paragraph 4: Criminal defendants are presumed innocent until a judgment of guilt is finalized.
• Criminal Procedure Act, Article 275-2 (Presumption of Defendant's Innocence) — Current (enforced 2026.10.2) — A defendant is presumed innocent until a judgment of guilt is finalized.
• Criminal Procedure Act, Article 307 (Principle of Evidence-Based Trial) — Current (enforced 2026.10.2) — Facts must be recognized based on evidence, and the recognition of criminal facts must reach a degree of proof that leaves no reasonable doubt.
• Criminal Procedure Act, Article 308 (Principle of Free Evaluation of Evidence) — Current (enforced 2026.10.2) — The probative value of evidence is determined by the free judgment of the judge.
• Criminal Procedure Act, Article 309 (Evidentiary Capacity of Coerced Confessions) — Current (enforced 2026.10.2) — Confessions suspected of not being made voluntarily cannot be used as evidence of guilt.
• Criminal Procedure Act, Article 310 (Evidentiary Capacity of Prejudicial Confession) — Current (enforced 2026.10.2) — When a confession is the sole prejudicial evidence, it cannot be used as evidence of guilt.
• Criminal Procedure Act, Article 325 (Judgment of Acquittal) — Current (enforced 2026.10.2) — An acquittal must be declared when an act does not constitute a crime or when proof of criminal facts is lacking.
• Civil Procedure Act, Article 202 (Principle of Free Evaluation of Evidence) — Current (enforced 2026.10.2) — The court shall determine whether a factual assertion is true through free evaluation of evidence, taking into account the entire purport of pleadings and the results of evidence examination.
• "The Presumption of Innocence as a Procedural Norm: Focusing on the Conflict between Guilt Allegations and the Presumption of Innocence" (2024) — DOI: 10.21795/kcla.2024.36.3.233 — The presumption of innocence is not a principle that presumes whether someone actually committed a crime, nor does it weaken because an investigation raises the probability of guilt; it functions constantly regardless of the strength of the charges. However, restricting fundamental rights through coercive measures requires a corresponding suspicion of guilt (Principle of Proportionality).
• "Application Requirements of the Principle of Presumption of Innocence and Its Relationship with the Principle of Prohibition of Excess" (2025) — DOI: 10.17007/klaj.2025.74.1.006 — The presumption of innocence functions as a rule concerning the location of the burden of proof and the degree of proof (judging rule), and as a rule prohibiting disadvantages presupposing guilt (treatment rule). The author considers that detention is not prohibited by this principle.
• "Legal Nature and Burden of Proof of Alibi Claims: Focusing on the Principle of Presumption of Innocence and Burden of Proof" (2020) — DOI: 10.22397/wlri.2020.36.2.21 — According to the principle of "in case of doubt, in favor of the accused" and the presumption of innocence, the prosecutor bears the burden of proving the criminal facts. Supreme Court precedents make it clear that the burden of proof for an alibi lies with the prosecutor, but in practice, the appearance of the defendant bearing it is noticeable.
• "Scope and Limits of the Principle of Free Evaluation of Evidence" (2019) — DOI: 10.23102/kaccs.2019.27..015 — Introduces the rationale of Supreme Court rulings that proof beyond reasonable doubt does not require ruling out every unreasonable possible doubt, and that evidence with probative value cannot be dismissed based on doubts without reasonable grounds.
• "Reasonable Doubt in the Degree of Conviction Formation to Recognize Criminal Facts as Guilty in Criminal Trials" (2012) — DOI: 10.16960/jhlr.13.2.201206.433 — Proof beyond reasonable doubt is required because a wrongful conviction of an innocent person is regarded as more unjust. Establishing guilt requires a high degree of proof, but providing concrete and objectified criteria remains difficult. The author also notes that it is difficult to consider the presumption of innocence as being properly guaranteed in Korean criminal trials.
• "A New Review on Reasonable Doubt and Proof in Criminal Procedure" (2015) — KCI ART001977922 — Proof beyond reasonable doubt is a fundamental right of the defendant. Among views suggesting this can be quantified, the difference measurement method supported by many Bayesians is extremely difficult to quantify and adopt in criminal procedure.
• "Clues to Reasonable Doubt: Focusing on the Contents of Court Judgments" (2014) — KCI ART001964380 — Analyzed 28 cases where lower courts and appellate courts disagreed. The factors causing disagreement were elements easily influenced by a judge's subjective judgment, such as the credibility of statements, the probative value and evidentiary capacity of evidence, and the interpretation of scientific evidence.
• "Court-Ordered Detention and the Principle of Presumption of Innocence" (2019) — DOI: 10.38133/cnulawreview.2019.39.3.169 — The conventional view classifies the content of the presumption of innocence into limits on personal restraint, prohibition of disadvantageous treatment, and the fundamental principle of proof (in case of doubt, in favor of the accused). The author disagrees with the conventional view that extends the presumption of innocence into a principle limiting personal restraint.
• "A Review of Constitutional Court Precedents on the Principle of Presumption of Innocence: Focusing on a Commentary on the Constitutional Court Decision 2010Hun-Ma418 on September 2, 2010" (2012) — KCI ART001687819 — The Constitutional Court has maintained that suspects before indictment and defendants must be treated in principle as if they are not guilty until a final judgment of guilt, that any disadvantages imposed must be limited to the necessary minimum, and that this applies equally to the restriction of fundamental rights in general legal life outside criminal procedures.
• "Crime Reporting and the Principle of Presumption of Innocence" (2020) — KCI ART002624618 — The Constitutional Court understands that the presumption of innocence applies to the realm of general legal life as well. The author considers that while this principle does not apply directly to news reporting, the media should also respect its constitutional value and refrain from treating suspects and defendants as criminals before guilt is finalized.