The Supreme court admits the real evidence in spite of the unlawfulness during the process of acquiring it. The reason of the theory is that truth-worthiness of the real evidence has not been changed by the fault of the investigation in gathering evidence. Considering the want of Destruction of Justice statutes, the Supreme court strikes the balance between the public interest and private protection by admitting the real evidence on all occasions.
The reformed Criminal procedure law is going to introduce the exclusionary rule. The §302-2 stipulates that "The evidence which is not gathered by lawful process should be excluded." Comparing with other developed countries exclusionary rule, it is too broad.
For instance, PACE act §78 (1) in England is “In any proceeding the court may refuse to allow evidence on which the prosecution proposes to rely to be given if it appears to the court that, having regard to all the circumstances, including the circumstances in which the evidence was obtained, the admission of the evidence would have such an adverse effect on the fairness of the proceedings that the court ought not to admit it." In Canada, the constitution §24 ② provides that “Where, in proceedings under subsection (1), a court concludes that evidence was obtained in a manner that infringed or denied any rights or freedoms guaranteed by this Charter, the evidence shall be excluded if it is established that, having regard to all the circumstances, the admission of it in the proceedings would bring the administration of justice in to disrepute."
Even in the U.S., there are lots of exceptions to the exclusionary rule. Good faith theory, harmless error rule, the standing, restrictive application in Miranda rule violation. collateral use are the examples.
The German's Beweisverwertungsverbote is the theory concerned about balancing the interest to protect the privacy. Thus basically it doesn't matter the manner of gathering the evidence. So it stats from quite different angle.
When it comes to our exclusionary rule, we must be prudent when we apply the rules to the real case. We don't have to exclude the real evidence solely because it is not obtained according to the process of law. We should take into account the motive of the police, the seriousness of the case, the deterrence effects, the influence on the administration of justice, the value of the evidence.
If the evidence is procured by private party, it should not be excluded. The criminal justice system don't have to depend on third party's action. Also there is the possibility that the third party or dependant will abuse the rule. There will be no remarkable deterrent effect, even if we remove the evidence on account of private party's illegal behavior.

【대상판결】대법원 1994. 2. 8. 선고 93도3318 판결
  Ⅰ. 사실관계
  Ⅱ 소송의 경과
  Ⅱ. 각국의 위법수집증거 배제법칙
  Ⅲ. 검토
  Ⅳ. 결론
 [abstract]

• 안성수(인천지방검찰청) | An SeongSu (Incheon District Public Prosecutors' Office)