The Code of Criminal Procedure requires that the facts of a crime must be proved beyond a reasonable doubt, which is called evidentiary jurisprudence. Evidentiary competence assesses whether evidence is legally qualified, while probative power assesses how much the evidence can contribute to the trier of fact. This ensures a fair and objective trial.
The Code of Criminal Procedure stipulates that the fact of a crime must be proven by evidence, and that the fact of a crime must be proved beyond reasonable doubt, which is called evidentiary jurisprudence. This means that judges are not allowed to arbitrarily recognize facts, which is a prerequisite for fair and objective criminal trials. Evidence therefore occupies a central place in the criminal procedure system. The Code of Criminal Procedure distinguishes between evidentiary and probative power of evidence.
The first is the legal qualification of a piece of evidence to be used as a source of proof. Evidence that is admissible can be used as a key fact in court, and a conviction can be based on it. Evidence that is not admissible cannot, in principle, be used to prove a fact. The requirements for admissibility are stipulated by law. The Code of Criminal Procedure specifies the conditions under which evidence must be excluded under three principles: the exclusionary rule of illegally obtained evidence, the exclusionary rule of confessions, and the rule of expertise. The common purpose of these principles is to realize a fair trial by guaranteeing the rights of the suspect and the accused.
The exclusionary rule of illegally collected evidence is a principle that denies the admissibility of evidence collected without following due process, and is aimed at deterring illegal evidence collection by criminal justice agencies. Derivative evidence, or secondary evidence, collected based on facts learned through illegally collected evidence, is also excluded under the exclusionary rule. This is known as the poisonous fruit theory, which states that if the primary evidence is a poisoned tree, then the secondary evidence derived from it is the poisonous fruit on the tree. For example, if a statement is obtained during an illegal arrest without a warrant, the statement is inadmissible, as well as the evidence obtained with the help of the statement. However, the secondary evidence may be admissible if the causal connection between the illegally obtained primary evidence and the secondary evidence is diluted or severed.
The confession exclusionary rule denies the admissibility of a confession if it was obtained by a law enforcement agency or court in a manner that limits its arbitrariness. Confessions are important evidence, but when investigative methods rely solely on obtaining confessions, they can lead to human rights violations and sometimes make it difficult to get to the truth. The exclusionary rule prohibits the coercion of confessions by making the subject of a confession voluntarily admit to the admissibility of the confession without physical or mental pressure.
The hearsay rule is the principle that expert evidence is not admissible. Hearsay evidence is oral testimony given by a person who has experienced an event, such as a defendant or witness, that is not given directly in court but is given indirectly by another person. There are two types of expert evidence: oral testimony and documents. The rationale for the hearsay rule is that hearsay evidence is subject to editing and manipulation by the person giving the evidence, that the defendant cannot cross-examine the witness in court, and that the judge cannot obtain accurate linguistic information because the judge cannot ask the witness directly in court and hear the answer. However, if the defendant agrees that the expert evidence can be used as evidence, the competency of the evidence is recognized, which is called ‘consent to evidence’.
On the other hand, unlike admissibility, probative power refers to the degree to which evidence can contribute to the determination of facts, i.e., credibility as the actual value of evidence. The evaluation of probative power is differentiated from the evaluation of evidentiary capacity, which only considers the presence or absence of evidentiary capacity. Evidence does not mean that it is probative, nor does it mean that it is admissible.
The assessment of probative value is left to the free judgment of the judge, a principle known as liberal evidentiarism. When evidence is presented with probative value, the judge is free to make a judgment about its probative value. The judge’s judgment must be based on reasonable grounds, and mere arbitrariness is not justified. In accordance with liberal evidentialism, the judge is free to pick and choose evidence, and in the case of contradictory evidence, it is left to the judge’s free judgment to decide which evidence to believe. Even if a witness is not credible, the judge may choose to believe certain parts of the testimony.
The Code of Criminal Procedure has strict rules on evidence to prevent judges from making arbitrary decisions. This is essential to ensure the fairness and objectivity of criminal trials. Evidentialism is therefore one of the important principles underlying the rule of law, protecting the rights of the accused and maintaining the credibility of the criminal justice system. In such a system, the process of thoroughly distinguishing between the probative and admissibility of evidence and evaluating the substantive value of each piece of evidence plays an important role in improving the quality of criminal trials.
