This blog post examines the difference between admissibility and probative value, focusing on criminal procedure law, and explores the role each plays in criminal trials.
The Criminal Procedure Act stipulates that criminal facts must be established by evidence, and the establishment of criminal facts must reach a level of proof beyond reasonable doubt. This is known as the principle of trial by evidence. This means that arbitrary factual determinations by judges are not permitted, serving as a prerequisite for enabling fair and objective criminal trials. Therefore, evidence occupies a central position within the Criminal Procedure Act framework. Criminal procedure law distinguishes between the admissibility and probative value of evidence.
Admissibility refers to the legal qualification of evidence to be used as material for proof. Admissible evidence can be utilized in court as primary material for establishing facts, upon which a guilty verdict may be based. Evidence lacking admissibility cannot, in principle, be used as material for establishing facts. The requirements for admissibility are prescribed by law. The Criminal Procedure Act codifies the conditions under which admissibility must be excluded through three principles: the exclusionary rule for illegally obtained evidence, the exclusionary rule for confessions, and the hearsay rule. The common purpose of these principles is to guarantee the rights of suspects and defendants, thereby ensuring a fair trial.
The exclusionary rule denies the evidentiary value of evidence collected without following lawful procedures, aiming to deter unlawful evidence collection by criminal justice authorities. Derivative evidence—secondary evidence obtained based on facts learned through unlawfully collected primary evidence—is also excluded under this rule. This is known as the “fruit of the poisonous tree” doctrine. If the illegally obtained primary evidence is like a poisoned tree, then the secondary evidence derived from it is like the poisoned fruit on that tree. For example, if a statement is obtained during an illegal arrest without a warrant, not only is the evidentiary value of that statement itself excluded, but the evidentiary value of any physical evidence discovered with the help of that statement is also excluded. However, if the causal link between the illegally obtained primary evidence and the secondary evidence is deemed diluted or severed, the secondary evidence may be admitted.
The exclusionary rule for confessions is a principle that denies the admissibility of a confession when investigative authorities or courts obtain it in a manner that restricts its voluntariness. While confessions are important evidence, overreliance on investigative methods solely aimed at extracting confessions raises significant concerns about human rights violations and can sometimes hinder the discovery of the truth. Accordingly, the exclusionary rule prohibits the coercion of confessions by recognizing the evidentiary value only of confessions made voluntarily, without physical or mental pressure.
The hearsay rule is the principle that hearsay evidence lacks probative value. Hearsay evidence refers to testimonial evidence—statements made orally by persons who experienced the matter, such as defendants or witnesses—that is not directly presented in court but is instead conveyed indirectly by another person. Such hearsay evidence includes oral hearsay statements and documentary hearsay evidence. The grounds for the hearsay rule include concerns about editing or manipulation by the person conveying the statement, the defendant’s inability to cross-examine the witness in court regarding the hearsay evidence, and the judge’s inability to obtain precise linguistic information since they cannot directly question the declarant and hear their responses in court. However, even if it is hearsay evidence, if the defendant agrees to its use as evidence, its admissibility is recognized; this is called ‘evidentiary consent’.
Meanwhile, probative value, unlike admissibility, refers to the extent to which evidence can contribute to the determination of facts—that is, the credibility of evidence as its substantive value. Evaluating probative value involves assessing the degree of a difference in the worth of evidence, which is distinct from evaluating admissibility, which only determines the presence or absence of admissibility. Evidence admissibility does not guarantee probative value, nor does probative value guarantee evidence admissibility.
The assessment of probative value is left to the judge’s free judgment; this principle is known as the principle of free evaluation of evidence. When admissible evidence is submitted, the determination of its evidentiary value rests with the judge’s free judgment. At this point, the judge’s judgment must be based on reasonable grounds; a purely arbitrary judgment is not justified. Under the principle of free evaluation of evidence, the judge may freely select evidence and, in cases of conflicting evidence, decide which evidence to believe based on their own judgment. Even testimony from an unreliable witness may be partially selected and believed by the judge.
The Criminal Procedure Act establishes strict regulations regarding evidence, aiming to prevent arbitrary judgments by judges. This is an essential element for ensuring the fairness and objectivity of criminal trials. Therefore, the principle of trial by evidence is one of the fundamental pillars of the rule of law, contributing to the protection of the defendant’s rights and maintaining trust in the criminal justice system. Within this framework, the process of rigorously distinguishing between the admissibility and probative value of evidence, and evaluating the substantive worth of each piece of evidence, plays a crucial role in enhancing the quality of criminal trials.
